Im working on a '93 pontiac trans-port van with the 3.8l motor. Its my
neighbors car and he broght it to me cause the muffler has a hole in it but i
noticed it wasnt running smooth at all. turned out that one of the coil packs
wasnt making spark at all. I got him a new coil pack and changed all the
plugs, and it runs way better now, but there is still a hesitation/miss at
about 1500-2000 rpms when revving the motor up quickly. It idles smooth and
if you give it gas slowly it accelerates smooth. but "stabbing" the gas makes
the engine stumble, and sometimes the check engine light comes on. this
almost feels like a miss but i thought at first it was a fuel starvation
prob. i checked fuel press and there is 40 lbs., even when this stumbling is
happening. I jumped the obd connecter pins and got the check engine light to
flash the codes. ive got code 12 and code 18. 12 is just the self check code
which you disregard but looks like 18 is for crank or cam sensor. IF i had a
bad cam sensor the motor would not start, so this could be the crank sensor?
also im wondering if dirty fuel injectors could be the cause. the car has
160K miles on it.
Those engines had a magnet on the camgear which gives the pulse to the
It was common for them to come loose and drop off. That may be what you are
seeing. If so, the engine will start and run with them that way. Just my 2
Ok that would make sense. I did go and change the plug wires yesterday
because there was some arcing across the boots when it rained outside. i
thought that would clear up all my troubles, and it did run smoother after
the wires were done, but there is still a rough running condition in certian
RPM ranges and the check engine light came on again (after clearing it out)
the cam/crank sensor fault is gone now. there is now a fault for the spark
computer , code 42. this car is posessed!!
i double checked my wires to make sure the firing order is correct. I think
maybe the spark arcing tricked the computer into thinking the timing was off
and throwing the crank sensor fault. but now this ignition module short thing
has got me stumped. i dont know much about how GM ignition systems are set up.
Im a BMW guy.
Napa and Autozone can test the ICM which is common source for this fault,
check the wiring to it also, look for corrosion on the mount base plate too.
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For some of them, at least, the ICM is a "slice of cheese" between the coils
the mounting plate, IIRC.
It has been a while, unfortunately, and my memory is no longer photo
I am sure that if I am wrong, someone will punish me>)
yeah i found the ICM and it is sandwiched between the coils and mounting
plate. I dont see any corrosion on the terminals or anything like that.
somebody mentioned that aoutozone can test these? is this true>? cna i just
take the unit to them or do they test it on the car? i know they can read
faults but i already have the fault code. i dont think they have the tools to
test this sorta thing
Sorry for losing track in this thread - can you refresh me with respect to
what you've done so far in addressing this? Without going back in the
thread I don't even recall what year the car is. Did you check the TPS yet?
That's a fairly common problem point with hesitation problems. I'm also
assuming you've cleaned the throttle body, etc.
Its a 92. but im not going to go any further with the thing untill i figure
out this fault code 42. the code is for ICM shorted to ground. I need to
either replace the ICM or find the shorted wire. could this fault have been
set due to the bad coil that i replaced?
thats how this all started, the car was only running on 4 cylinders. i found
the bad coil, replaced it, replace the plugs and wires, and it runs alot
better, but still kinda misses/stumbles at certian rpms. there is a check
engine light and fault 42 now
Message posted via CarKB.com
Here's something I dug up.
Typical causes for this code include:
1) BYPASS line is open or grounded
2) EST line is open or grounded
3) PROM or CALPACK not seated properly in the ECM
4) Poor connections between ignition module and ECM
5) Poor routing of EST harness and/or poor quality ignition wires (EMI
induced electrical noise)
6) Faulty or incorrect ignition module
7) Faulty ECM
This came from http://www.gnttype.org/maint/malf.html#42
thanks for the info!!
Well i decided to just grab an icm and 3 coils from the junkyard. they only
charged me 15 bucks. I put the icm on but the car wouldnt start. It came off
a buick park avenue but the 3.8L engines should all be the same, no? anyway i
decided to try it again with the original icm and 2 of the junkyard coils.
(the 3rd was brand new) and it runs fine!! i guess it was a coil that was on
the verge of failing. i could have had this all fixed if i would have done
all 3 coils in the beginning. just weird how the ECM was throwing all these
weird faults at me. kinda throws you off base,.
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