3.8L hesitation

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.
--
Message posted via http://www.carkb.com


Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Those engines had a magnet on the camgear which gives the pulse to the sensor. 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 cents
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
HLS wrote:

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.
--
Message posted via http://www.carkb.com


Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
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.

----== Posted via Pronews.Com - Unlimited-Unrestricted-Secure Usenet News==---- http://www.pronews.com The #1 Newsgroup Service in the World! >100,000 Newsgroups ---= - Total Privacy via Encryption =---
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Shep wrote:

thanks for the info. Where is the ICM? is it simply the plate that the coils are mounted to? this question probably sounds stupid but like i said i really only work on imports
--
Message posted via http://www.carkb.com


Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

For some of them, at least, the ICM is a "slice of cheese" between the coils and the mounting plate, IIRC.
It has been a while, unfortunately, and my memory is no longer photo correct.
I am sure that if I am wrong, someone will punish me>)
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
HLS wrote:

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
--
Message posted via http://www.carkb.com


Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

I believe you're correct on your assumption. I think about all they can do is scan codes.
--

-Mike-
snipped-for-privacy@alltel.net
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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.
--

-Mike-
snipped-for-privacy@alltel.net
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Mike Marlow wrote:

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
http://www.carkb.com/Uwe/Forums.aspx/gmc/200804/1
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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
--

-Mike-
snipped-for-privacy@alltel.net
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Mike Marlow wrote:

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,.
--
Message posted via http://www.carkb.com


Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Related Threads

    Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here. All logos and trade names are the property of their respective owners.