--------------
[ www.tricomponent.com/productlist/hardprts.php ]
TRANSMISSION PARTS (Uncertain if they have the "Repair Kit") for TH-125 (3.1 Lumina) / / / Tri-Component, 973 Brook Ave
Bronx, NY 10451-4209
Toll free: 800-366-3874
Local: 718 402-2400
Fax: 718 402-2467
email: admin@tricomponent.com
--------------
[ www.txchange.com/sk.htm#General Motors ]
[No prices given; not sure if this specifically repairs the "stuck throttle valve" problem; - rj]
SK 125 /
THM 125 /
1980 up /
Corrects/prevents/Reduces:
3-2 clunk; lockup shudder; reverse slip; converter drain back delay;
late shifts; soft 1-2; band failure.
Most items are not available on-line. Our hours are eight A.M. to five P.M. Monday through Friday Pacific Time. Please call 800-776-1191, or 503-284-0768. We accept all major credit cards. Whether you are an experienced transmission expert or have never purchased a transmission or transmission part before, our experienced and knowledgeable sales people are waiting to help you.
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[Lumina]
1994 Chevrolet Lumina APV/Minivan: Restyling shortened the nose, and the "APV" suffix was replaced by "Minivan." Overall length shrunk three inches, and a driver-side airbag was added. Integrated child safety seats became available in 7-passenger models. Traction control became an option later in the year.
1995 Chevrolet Lumina APV/Minivan: Other than extended-life transmission fluid, little change was evident.
1996 Chevrolet Lumina APV/Minivan: A new 3.4-liter V6 became standard, as all models got seven passenger seating and standard air conditioning. Lumina Minivans disappeared after '96, replaced by an all-new steel-bodied Venture.
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{Crate Engine:]
A crate engine is a ready to run engine in a crate. Crate engines are usually put together with a whole bunch of different parts from different kinds of cars. Crate engines are also alot cheaper than regular engines, the same quality for less money.
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[Fuel Pressure Regulator]
[www.autosite.com/garage/encyclop/ency07a.asp ]
The best thing I've seen for catching inadequacies is an extremely accurate (and quite expensive) on-car fuel system tester from Hickok that measures flow against an internal standard injector, gives the static flow rate in lbs. per hour or grams per minute and dynamic flow rate in percent, finds leak- down, checks system volume and pump pressure recovery, looks for shorts and opens in the solenoid windings, etc. It takes five minutes to hook up, then you can be pretty sure of uncovering even the subtlest of troubles.
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[www.babcox.com/editorial/cm/cm120230.htm.]
FUEL PRESSURE.
To provide the exact amount of fuel the engine needs under all conditions, the pressure inside the fuel lines that supply the injectors changes. When the driver steps on the gas and opens the throttle, intake vacuum drops. To deliver the same amount of fuel, pressure has to go up along with injector on time. Likewise, when the driver lets up on the gas and the vehicle decelerates, less fuel is needed to keep the engine running. Fuel pressure can drop along with injector on time.
The device that makes all of this happen magically is not the fuel pump (which runs constantly and provides steady pressure to the engine), but the fuel pressure regulator. On most engines, a fuel pressure regulator is mounted on the fuel rail that supplies the injectors. Inside is a diaphragm valve connected by a rubber hose to intake vacuum. When vacuum goes up, the valve opens and allows excess pressure to vent through a return line back to the fuel tank. On newer vehicles with "returnless" fuel injection systems, the pressure regulator is located back in the fuel tank just after the pump.
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[ faq.f650.com/GSFAQs/FuelPressureFAQ.htm ]
The typical fuel pressure regulator should last a long time, typically for the life of the vehicle, [motorcycle msg board - rj] unless it gets clogged up with dirt, or rubber particles, shed when aging fuel hoses crack internally and are flexed to replace the primary fuel filter. For this reason, it is prudent to replace the rubber fuel hoses at the same time as the primary fuel filter to prevent clogging up the expensive fuel pressure regulator with cracked rubber "chips".
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[forums.vmag.com/suvjim0199/messages/4056.html ]
...Surging and bad gas mileage are sure signs of eithe a bad fuel pressure reg. or leaking fuel lines or "nut kit"
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[http://www.misterfixit.com/94Blazer.htm]
...so I installed a new cap, rotor, wires, module, and plugs. This fixed the arcing problem but not the surging/stall. I checked the fuel pressure and it was within spec but on the low side. I put my scanner on and found no codes and erratic readings from the sensors due to the surge. I eliminated the TPS, MAP, IAC, EGR and O2 sensors by individual testing.
The engine backfired through through intake so I suspected a lean condition. I rechecked the fuel pressure and found that when I snapped the throttle, the pressure dropped from 55 to 41psi. (spec is 54-64 psi). I then pinched of the return line and had 65 psi. The fuel pump was good. It was the CPI unit [central port fuel injection - i.e., one injector for all cylinders (as in, my car don't got this) - rj] which houses the fuel pressure regulator that was bad. The unit was less than 2 years old, and very expensive ($360) so I was surprised to find that it was bad. The replacement took about 1.5 hours and was very easy. You pull the upper plenum and it is right there, no special tools required. The truck is now running great. I hope this info is useful to someone and not to wordy.
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-----
{VAN STUFF}
[ www.babcox.com/editorial/us/us90334.htm ]
When I started as a kid working in the gas station, our mechanic, "Greasy Joe," diagnosed most problems by placing one end of a sawed-off broomstick handle on the engine and the other end in his ear. This homemade stethoscope diagnosed a lot of beat-out connecting rod bearings and worn wristpins. But the rest of Joe's diagnostic portfolio was basically an association of symptoms with component failures. Vapor lock was caused by hot days and overheated fuel pumps. Closed-up ignition contact points more often than not caused sluggish engine performance. Surging and stalling was caused by worn fuel pumps, clogged fuel filters and collapsed fuel pump inlet hoses.
With the MAF disconnected and operating in the default mode, the snap throttle response was crisp while the idle was smooth and uninterrupted by the previously noted engine miss. With the MAF re-connected, all the previous symptoms, including the stumble and slight engine miss, returned. This seemed to indicate, based upon symptom-based evidence, that the MAF sensor was indeed defective. But, even though I reluctantly ordered a new MAF sensor, something lingered in the back of my mind that said the MAF wasn't the cause of the problem.... After flushing the injectors, adding a heavy-duty injector cleaner to the fuel tank and topping off with quality gasoline, a test drive proved the theory. The engine accelerated without hesitation. The only nagging problem left was a constant engine miss during acceleration....With the substitute wires attached, the Probe ran perfectly. [t least it shows the MAF sensor **might** be it; see if it runs differently disconnected (and disconnect battery 3 minutes to reset PCM) -rj]
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[http://retro.co.za/efi/DIY_EFI/1998/efi3-321.txt ]
[88 Buick 3.8L] My parents bought it new in 88. They decided to get rid of it about 5
years ago because it had always idled rough, left them stranded once
(crank sensor), and was intermittently prone to stalling when you let
off the throttle at low speed around town. Figuring that an intermittent
will eventually get bad enough to be continuous so that it could be
diagnosed, I bought the car...All cylinders 140-150 psi compression cold.
Lynn, have you tested the MAF? while it is idling, rap it firmly a
few times... if it stalls, it's bad... I've seen this many times.
And TWong29770@xxx.com wrote:
"I forgot, one more thing to check is the MAF sensor, check it by lightly
tapping the body of the MAF sensor while the engine is idling. If there is a
problem with the MAF the engine will stall when you tap it. Use a large
screwdriver handle or a rubber mallet, I mean TAP not BASH!"
I've been the MAF fail route before. Twice. The first time it loaded up
and ran full fuel. I dug out the Chilton's and web searched for
diagnostic procedures. WRONG! They said to look for a varying voltage
from the MAF - NOT. Because the ouput signal from the MAF is variable
frequency so it always reads about 2.5 volts. Of course I only found
this out later, but replaced the MAF and it was indeed the problem. The
cheapo replacement unit crapped out about 3 months later by cutting out
completely (engine died at 75 MPH). It started back up after a cool
down, and this time the tap test was completely effective.
------
...check for vaccuum leaks first. Common places on the 3.8L SFI is the vaccum
resevior hose at the resevior, ...Also check your vacuum booster. Mine leaked
horribly.
....you
may want to try replacing the DIS module which is the module that is what the
coils are mounted to [Ignition Module - rj].I was a GM tune up mechanic for many years, and we had many problems with the
early 88 DIS modules.
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{MASS AIR FLOW (MAF)] 1993: 3.8L Year: 92-93 $208.65 their price: $146.06
1994: 3.8L 94-96 $208.65 $146.06 [GET IT? THEY'RE DIFFERENT FOR '93 & '94 - RJ]
Regular Auto Parts Store Prices: 1993: Delco Stk. No.: AC DELCO 213-230 151.05 core dpst.:66.00 ) generic PRICE: 105.32 / CORE:75.00
1994 (Delco Stk. No.: AC DELCO 213-270 - [Different # than '93 Part no.!] 151.05 core: 66.00 [Same price as '93]) reg part generic PRICE: 105.32 / CORE:75.00
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[http://www.me.mtu.edu/~edan/talon/digest-01.28.99.html ]
I have peen plagued with a bad idle for a long time now. I have replaced 3
Idle control valves. After some time of this happening, I started experencing
violent hesitation and bucking during low end acceleration. After about 3000
rpm, it seems to smooth out. I have checked my ECU for leakage.
I just
recently replaced my TPS. After replacing the TPS, the symptoms were not as
prevelent, but yesterday it was up to its old behavior again. If I unplug my
MAF the idle seems to smooth out, but I am not sure that this may be putting
the car into "limp mode" and using all preset values and not monitoring any
sensors. I am also hesitant to drive the car without the MAF because I don't
understand how the computer can compensate without it. I cannot find any way
to check the MAF in the service manual. Does anyone know how to check the
MAF? Has anyone experienced these symptoms and what was your remedy?
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{Distributorless Ignition System (DIS]
[www.mightyap.com/Data/TT76.pdf.]
The DIS System consists of 2 or 3 separate ignition coils, an ignition module, a crankshaft sensor, a network of wiring and the Electronic Spark Timing Circuit within the Electronic Control Module (see Fig. 1). Precise and consistent signal inputs are imperative or a no-start condition is inevitable. The DIS System must distinguish between crankshaft sensor signals and other signal noises such as Radio Frequency Interference. This requirement means the module waits for specific voltage signals before identifying the fluctuating crankshaft sensor output voltage as the proper signal, to begin the firing sequence.
The crankshaft sensor signal varies with engine speed and air gap spacing. The signal strength can vary from a positive 200 millivolts AC to a negative 200 millivolts AC, at very slow cranking speeds; to a positive 150 volts to a negative 120volts, at high speeds. The voltage must rise above a certain positive threshold and then move through zero volts on the negative transition. At this point the module will trigger or count off the zero voltage crossing of the waveform. However, until the voltage reaches the threshold value, the module will not recognize the zero volt transitions and count the signals, thus a no-start. A NARROW GAP The crankshaft sensor is mounted on the bottom side of the DIS module and protrudes into the engine block.
There is an approximate .050 inch airgap between the sensor and the crankshaft reluctor, when installed. The gap is critical, as the signal output is in relation to engine cranking speed and air gap spacing. Air gaps smaller than .030 inches will create higher than normal voltages and some high speed abnormalities with the threshold volt-ages, internally in the DIS module, and potential circuit damage. Air gaps larger than .070 inches will result in weaker voltage signals and some engine starting problems due to weak and erratic signals. The signals can be too weak for the module to count. When installing a crankshaft sensor and module, make certain it is properly torqued and never shimmed for any reason. The reluctor is cast into the crankshaft. It has six evenly spaced slots cast into it, 60 degrees apart.
A seventh slot is positioned 10 degrees from one of the other slots and functions as a "sync pulse." As the reluctor rotates past the sensor, the slots change the magnetic field of the sensor, creating induced volt-age pulses. By comparing the time between pulses, the DIS module can recognize the pulse representing the seventh slot or "sync pulse," which starts the calculation of the ignition coil firing sequence. The second crank pulse following the "sync pulse" signals the DIS module to fire the #2⁄5 ignition coil, the fourth crank pulse signals the module to fire #3⁄6coil and the sixth crank pulse signals the module to fire the #1⁄4 coil, on a 2.8L engine.
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[Hesitation}
[www.autosite.com/garage/encyclop/ency09c.asp ]
Strictly defined, hesitation is the inability of an engine to speed up instantly from idle when requested to do so by the driver's right foot, but I'm going to add reluctance to accelerate from any point in the rpm range. Even an old rag of a powerplant with bad valves and worn-out rings should be able to do that, so internal engine problems are low on the list of potential culprits. Whenever you encounter this condition (lag, flat spots, stumble, bog, etc. are synonyms you're apt to hear, and stalling is this malady's terminal stage), run through the following possible causes in your mind before you do anything:
Too little extra fuel is being supplied during acceleration. /
The mixture is too lean while the engine's cold. /
The intake air is too cold. /
A vacuum leak is present. /
EGR is occurring before the engine is warmed up. /
There's a problem in the ignition secondary system. /
The spark advance isn't right.
With a feedback carb or EFI system, a bad sensor signal is causing the computer to go into its limited operating strategy, also called the fail-soft or limp-in mode.
It will be a very rare case indeed that isn't the result of one of the above. Concentrate on the symptoms as you take a test drive and see if your experience aims your suspicions in a particular direction. Just be careful not to jump to any unfortunate conclusions.
...fixed them in no time flat by reconnecting a vacuum motor line or installing a missing hot air duct.
...
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[http://www.users.bigpond.com/INTERJECT/Problem1.htm]
CAUSE: - CHECK ALL SENSOR GROUNDING POINTS ARE UNDER 0.03V.
IF ANY ARE OVER THIS, THERE MAY BE PROBLEMS WITH THE CARS FLAT SPOT ABOVE IDLE.
REMEDY - REPAIR / REPLACE GROUND CONNECTIONS. ...SPARK PLUG LEADS, LEADS ARCING ACROSS...[any wiring harnesses crossing the spark plug leads]
Other causes: LEAKY FUEL PRESSURE REGULATOR. (???:) ALTERNATOR DIODES FAULTY, TO MUCH AC CURRANT INTERFERING INTO THE DUTY CYCLE (DC?) CURRENT OF THE IDLE STABILISER VALVE.(???)...SYSTEM IS NOT MATCHED PROPERLY TO A NEW OR SECOND HAND ENGINE, WRONG INJECTORS FITTED TO A LARGER ENGINE, STANDARD INJECTORS FITTED TO A TURBO ENGINE [Not Applicable, it's the same engine, AND it worked OK before; BUT something may be mismatched in a way that makes it too sensitive to whatever "damage" caused the defect- RJ] ...[While I'm talking to myself... the FUEL PUMP: was SLIGHTLY low [41 PSI when it's "supposedta be" between 42 - 48... and it IS electronic...BUT what's it got to do with the battery project?)
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[BLOCKED EXHAUST/CATALYTIC CONVERTER test]
For the possibility of an exhaust restriction or improper valve timing by performing the following test.
With engine at normal operating temperature, connect a vacuum gauge to any convenient vacuum port on intake manifold. /
Run engine at 1000 rpm and record vacuum reading. /
Increase engine speed slowly to 2500 rpm. Note vacuum reading at steady 200 rpm. /
If vacuum at 2500 rpm decreases more than 3" Hg from reading at 1000 rpm, the exhaust system should be inspected for restrictions.
Disconnect exhaust pipe from engine (or remove 0@ Sensor - RJ) and repeat Steps 3 & 4. If vacuum still drops more than 3" Hg with exhaust disconnected, check valve timing.
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...What I have found is, that if I disconnect the O2 sensor, the problem
goes away, but then I get the awful smell from the converter from what I
guess is a rich mixture
...
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[Catalytic converter: test for Plugged condition]
[www.2carpros.com/topics/catcon1.htm ]
To test for a plugged converter, drill a small hole in the exhaust pipe right before the catalytic converter. Install a temporary hose fitting and attach a long rubber hose and a 0 to 10 pound pressure gauge. With the gauge inside the car, drive up a hill or accelerate and read the pressure. Normal is 2 to 3 pounds, restricted 4 pounds or higher. The drawback to this method is the small hole will need to be welded shut after the test; a minor job if you have a welder.
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[Torque Converter Clutch]
[ www.automotivehelper.com/topic131702.htm ]
I had the same problem with my 93 grand prix and it ended up being a simple temporary fix that you should try. it worked for me. My neighbor works at a GM dealership and i took him for a test drive in it. he said he sees this alot in Grand Prix's. Its the Tourque converter clutch on the front of the transmission. i guess its a bitch to fix but what you can do is just disable it and the car runs fine. there is an electronic plug on the front of the transmission that runs the TCC and if you unplug it your car will run fine and you don't need to change the whole TCC. He mentioned that it would hurt my gas mileage and that would be it but i haven't noticed that much of a difference. I hope this helps...it worked beautifully for me. good luck
--------------------
{"How To Repair" http://autorepair.about.com/library/weekly/aa011703e.htm ]
Wiring Harness:
Computer-Controlled Vehicles: The 4L60 transmission's torque converter clutch (TCC) is activated by an electric signal from the vehicle's engine control module (ECM). The 4L60 transmission uses a five-pin TCC connector that was introduced on 1993 model vehicles. The wiring harness in a 1983-1992 vehicle with a four-pin TCC connector can be modified to fit the transmission's five-pin TCC connector as follows:
Using the terminal removal tool supplied with the transmission assembly, remove all of the wires from the five-pin TCC connector wiring harness that is supplied with the transmission. Then transfer the wires from the vehicle's four-pin TCC connector to the five-pin connector. Remove the wire from the four-pin TCC connector marked "A" and insert it in the "A" terminal of the five-pin TCC connector. Repeat this procedure for the "B", "C", and "D" terminals, transfer the wires from the four-pin connector to the same respective terminals on the five-pin connector. (Remove the plug in the five-pin connector's "C" terminal before transferring the wire.) The fifth terminal "E" is not used in this conversion; do not connect a wire to it.
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[Not "Intermittent" per se, but...]It could be a valve that is not seating correctly, either burned or possibly hanging so it doesn't close all the way, or it could be a bent valve also not allowing it to seat properly.
The cam timing was off. Buick has supplied older [this is an '86] motors with a nylon coated cam gear. After about 90K miles the nylon starts to get brittle. The pieces break off and sit in the bottom of the oil pan. After most of the nylon has broken off, the aluminum gear underneath the nylon begins to wear off, also settling at the bottom of the oil pan. Now for all of you who are wondering if you are about to lose timing gears - Is there a predictor that warns Buick (and most GM products) that there is trouble in River City?
At your next oil and filter change punch a hole in the oil filter that you have just removed. Let the oil drain into the coffee can through a clean cloth. If you see a lot of fine aluminum power in the oil or on the rag you probably are a few miles from a timing gear failure. If you also see fine pieces of light green (Buick color) nylon in the filtrate - same deal.
...engine had a random "tumbling rock" sound that only occurred when the engine was hot. I purchased a stethoscope. it did not change with engine speed. The noise was at the timing cover. a common problem with the Buick 3.8L V6 from 1985-1987.
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[Harness wires to sensors, injectors, etc] I had found a SOFT SPOT in the wire. There was a six inch length of wire that was no longer wire. There was nothing inside the insulation but copper oxide! Green powder... It was up against a hot area.
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{Compression Test While Engine Is Running]
Put all spark plugs but one back in. Ground that plug wire to prevent module damage. Disconnect that injector on a port fuel system. / Put your compression tester into the empty hole. The test can be done without a Shrader valve, but most people recommended leaving the valve in the gauge and "burping" the gauge every 5-6 "puffs".
Start the engine and take a reading. Now goose the throttle for a "snap acceleration" reading. Reading should rise. Write it down NOTE: Don't use the gas pedal for this snap acceleration. The idea is to manually open then close throttle as fast as possible while without speeding up the engine. This forces the engine to take a "gulp" of air.
ANALYSIS: Running compression at idle should be 50-75 psi (about half cranking compression). Snap throttle compression should be about 80% of cranking compression.
EXAMPLE 1 - RESTRICTED INTAKE CYL STATIC COMPR IDLE -RUNNING COMPR - SNAP Cyl 1 150 75 80 If Snap reading is low (much less than 80% cranking compression), look for restricted intake air- severely carboned intake valve, worn lobe on cam, rocker problem, "shutters" mispositioned in the runners. (Toyota, Vortec etc. with variable runner length) Comparing measurements between cylinders is important.
EXAMPLE 2 - RESTRICTED EXHAUST CYL STATIC COMPR IDLE -RUNNING COMPR - SNAP Cyl 1 150 75 180 If snap measurements are significantly higher than 80% of cranking measurements, look for restricted exhaust on that cylinder-such as worn exhaust cam lobe, or collapsed lifter. Or, if they are all high, look for a clogged cat converter.
When you do a normal compression test, you are checking cylinder sealing, not cylinder breathing. If one cylinder reads low running compression compared to the rest it means that the air didn't make it in. If one cylinder reads high, the air didn't make it out (and the next pulse of air raised the pressure).
[RESTRICTED CATALYTIC CONVERTER & VACUUM:]
Vacuum Gauge Reading: Slow return after revving: Snap throttle to WOT until engine at 2500 rpm. then release. Vacuum should drop to 0 then go to 25-28 then back down to normal. If vacuum returns slowly and doesn't peak the rings may be worn. If there is a long delay, look for a restricted exhaust. If the exhaust seems restricted, disconnect at manifold and repeat the now loud test. OR: Remove the oxygen sensor and start it up. The hole where the oxygen sensor was will relieve the back pressure and it should run a tad better. If so, then disconnect the exhaust pipe at the exhaust manifold and try it again. If it is a clogged cat it will scream like a banchee and rev up to its normal 4000 rpm.
If the vacuum is say 21 inches at idle and like 15 inches at 1500 then the cat is likely clogged.
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[INTERMITTENT PROBLEMS]
[http://www.misterfixit.com ]
...There is a block of 3 relays on the RF fender behind the headlight. They are all open to atmosphere at their bases. ...
[ www.misterfixit.com/izuzzu.htm ]
....A few messages for you. First, is GET THE SERVICE MANUAL!! Second is that throwing parts at a problem is not the efficient way to solve a problem, a syndrome I call the Dealer Syndrome. Third is, don't give up;... [Long story of tracing every part to find an intermittent, then finally:]The 12 volt supply looks OK and shaking the engine has no effect. The computer's ground supply wire reads 12 volts also until I shake the engine then the voltage starts jumping all over the place. Finally we've zeroed in on the problem but I've checked all ground wires in the engine compartment and non were lose? After checking this wires color code the search is on. THE CULPRIT IS FINALLY FOUND. A 10 CENT RING CONNECTOR!
On the front of the intake manifold is what looked like a large ground connector wrapped with wire harness tape and securely bolted in place but when the tape was removed it was found that there was one ground wire securely in place on one ring connector. Underneath were two more ground wires one was the computers ground wire! These were connected to another ring connector which had broken away at the connector base probably due to engine vibration but then remained partly connected because the tape was holding it in place.
Here's an explanation as to why this made the car act so crazy. When the engine was not running the tape would hold the broken connector against the good connector completing the computer's ground circuit. When the engine was running the vibration would cause the loose connector to vibrate resulting in a voltage drop to the computer. When the vibration was great enough, or a bump was hit, the voltage would drop below what it needs to work. It would then shut down or basically loss its mind (like I almost did) .
But now the jack hammer like vibration of the pistons is gone causing the connector to reconnect which causes the computer to come to. Realizing something's not right it puts the engine light on and goes into fail safe mode. Fail safe mode runs the engine with fixed timing and fuel injection to bypass systems the computer thinks may have failed. But the engine doesn't run well in this mode so you guessed it, more vibration, the voltage drops, the computer quits and your bucking along it 15 mph. Finally when you stop the car and try to check for codes the only code is 12 meaning the computers OK and they're are no codes stored because the computers memory has been erased by the power loss. So if you've got a really strange intermittent problem check the grounding wires around the engine real close.
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[ http://www.troublecodes.net/articles/solveint.shtml ]
For mechanical intermittants, the Wiggle Test is the most effective. Wiggle every wire related to the suspect circuit, push and pull on each wire in each connector, tap suspect assemblies firmly with a screwdriver handle, flex every inch of a wiring harness, and examine the internals of each plug-jack connector.
The components which are most likely to fail are those which are subject to the most vibration, and those which are subject to the harshest environment, which leads to corrosion. For example, battery terminals need to be cleaned periodically, because they are subject to a light sulfuric acid vapor atmosphere. Braided ground straps almost always fail from these factors.
One final note about troubleshootong intermittants; It does no good to test components if the car is not acting up at the time. If the car is behaving normally, then anything you test MUST, by its' nature, test GOOD.
It's a harsh fact of life among electronics troubleshooters that a part can test OK, but fail in actual operation. This is because a tester tests with only a TINY amount of power, but the component fails only under the stress of higher voltage and current. Regarding the stresses on electrical/electronic devices, the components which are most likely to develop mechanical intermittants are electro-mechanical devices, such as MAP sensors and TPS potentiometers. The components most likely to develop thermal intermittants are those which contain semiconductors, such as ignition modules and voltage regulators.
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[Keywords: Intermittent Engine Surging (completed: Search Page 5) Also: repl. "Surging" with "Hesitation" ]
[www.zhome.com/ZCMnL/PICS/hesitation/hesitation.html ]
] There are more than 33 items, which if faulty, that can cause engine hesitation and stumble problems:
Worn or defective spark plugs /
PCV hose air leak /
Air flow meter /
Intake valve deposit /
Exhaust gas sensor /
carbon canister /
fuel pressure /
fuel pressure regulator /
Injector /
injector circuits /
ignition coil and circuits /
Transistor ignition unit /
ECU harness connector /
ECU power supply & ground /
ECU /
AAC valve /
Air regulator /
clogged idle screw /
Battery /
alternator /
EGR /
Temp sensor /
Temp sensor connector /
Throttle position sensor /
Idle switch /
Cone Air filter /
Crank angle sensor //
Fuel temp sensor /
Speed sensor /
Incorrect timing belt installation /
Crank Angle sensor and circuits /
Ignition Timing
5.3 Wiring faults
Is your hesitation problem intermittent? If so the chances are that its an electrical connection- whether it be a connector, a relay contact, or a crimp joint in the wiring, or a soldered joint on a printed circuit board. Are there any signs of green deposits on wiring harness connectors or sensor connectors? Note that wires are crimp jointed to the connectors, so not only can you get contact failure between the male & female part of the connector, but also at where the wires run into the connector. I've noticed connectors at the front of the engine (the two temperature sensors) are much more corroded than those at the back of the engine (exhaust gas sensor, variable valve timing control solenoid etc). The other connector which can get really dirty, is the fuel pump connector, located on the outside of the car, but accessed through a panel underneath where the spare wheel is.
If you are experiencing intermittent problems, you might find page EF & EC 47 in the manual helpful. Here, there are some tips on how to try and force an intermittent fault to show up. For example, race the engine rapidly to see if engine movement causes electrical breaks, wiggle connectors etc. It may be necessary to connect up LED's (light emitting diodes) at various points in the circuit, so when the fault occurs, you can spot it immediately.
After many years, connectors can be a source of problems. Unplug any suspect connectors and squirt some WD 40 or CRC 556 into it. Inspect the wires that go up to the connector closely. If the copper in the wire has a coating of copper oxide (black colour), then you may have to dismantle the connector, clean up the wire and solder it to the terminal. What happens here is that black copper oxide is an insulator, so over time your crimp joint can go open circuit as the surface of the copper wire turns from copper to copper oxide.
Another potential source of difficulty is the fuel evaporative emission control system.I think you can get too much vacuum in the tank which then prevents the fuel pump from delivering full fuel pressure to the injectors. When I changed mine, it was slightly clogged ( a black deposit) , and reduced the fuel pressure by about 2 psi across it. Fuel pressure is around 43 psi, more about that later. To test for this condition, disconnect the canister purge hose & plug it. If you want to remove the carbon canister for checking (there's a valve in it), allow for a bit of cursing if there is stuff in the way. To get at mine, I had to remove the front bumper. Of course, in my case there was nothing wrong with it.
I was having problems with my engine missing on my '90 300TT a few months ago. I took it to the dealer at least 5 times for it. The last time I asked to talk with one of the techs, he opened the hood with engine running wiggled a connection which killed the engine. He proclaims "Well, there's your problem."
Apparently, the connection to the crank angle sensor [Any sensor connection may do this - rj] can get loose and corroded, compromising the connection and causing an irregular miss. He cleaned and crimped the connections and no problem ever since.
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[ www.troublecodes.net/articles/ECMreset.shtml ]
If the vehicle is having intermittent driveability problems such as surging, bucking and/or stalling and the CEL (check engine lamp) is seen either solid or flashing with no trouble codes being stored then, there is a good chance that a reset is occurring. This can sometimes be seen with a scan tool as "NO DATA" or, the scanner seems to "freeze up" while the reset is occurring.
Any time you have an intermittent driveability problem with no CEL or stored trouble codes the power, ground and reference circuits should be checked by making sure all connections are clean and secure. The ECM can't store codes if it doesn't have power or ground circuits. I've found that the ground circuit that is at the thermostat housing on some GM vehicles is a potential ECM ground problem so, I add a ground wire from the battery negative post to the ground at the thermostat housing. I've also found ground circuits that were attached to a head bolt, and the bolt was broken. So if you have a ground circuit at a head bolt be sure and check the bolt.
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Most convertors these days have a honeycomb screen inside of them, these honey comb screens are coated with platinum to aid in superheating the exhaust to help burn any HC's left over from the combustion process.
Sometimes the screens melt or collapse inside and partially or completely block the path of the exhaust, which can create enough backpressure that the engine cannot breath well enough to run properly,
eventually the entire inside of the convertor will melt and sometimes shoot sparks and out of the exhaust.
you may have a failing fuel pump... / On my car, I think the diaphram in one of the valves is bad, but I haven't had time to check further... / don't forget to check the EGR... /
[www.babcox.com/editorial/us/us80312.htm ]
Scenario #2: An engine starts normally one day, but not the next. It cranks but refuses to start the first or second time, but may start normally after it sits awhile. The condition does not seem to depend on temperature or humidity. Something is obviously disrupting spark or fuel, but what?
The trick here is to catch the engine when it is acting up. If there's no spark, check the crankshaft position sensor or distributor pickup and module. If there is spark, check the injectors and fuel system. Is the fuel pump working? Are the injectors buzzing? No buzz means no injector driver signal from the PCM. The underlying cause might be a bad injector relay, no trigger signal to the PCM or a bad driver circuit inside the PCM. If there's also no spark and the vehicle is a Chrysler with an ASD (auto shutdown) relay, it's probably a bad relay because the relay supplies voltage to both the fuel pump and the ignition coil.
If the coil, fuel pump and PCM are all hot but there's no injector signal from the PCM (which you can check for at the injectors with a noid light), the driver circuit in the PCM may be bad - or one of the injectors may be shorted and pulling down the PCM driver circuit. Check the resistance of each injector before you condemn the PCM.
If there's no fuel and the pump isn't running, the pump may have a loose or corroded wiring connection, or a bad relay. If the vehicle has a safety inertia switch that cuts off the fuel pump in case of an accident, check that too.
Scenario #4: An engine suddenly quits running, but then starts again and runs normally. The cause may be the loss of an important sensor signal such as the crankshaft position sensor signal (distributorless ignition systems) or the ignition trigger signal (engines with distributors). Most of the old Ford Thick Film Integrated (TFI) modules that would quit working when they got too hot have been replaced, but there are still a lot of them on the road. Older GM HEI ignition modules also were prone to this disorder - especially if someone replaced the module in the distributor and forgot to apply the heat sink grease underneath to prevent the module from overheating.
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[www.c4vettes.com/ecm.htm.] 