91 3FE - No power to ISC

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STICKP

STICKP

Joined
Dec 12, 2016
Threads
3
Messages
31
Location
Wilmington, NC
I have replaced my ISC with one that is definitely good, however, I'm still not getting any power to it. I don't hear the click when I cut the engine off, and it's behaving exactly like my original that I thought had gone bad.

Any ideas on what may cause this. I just adjusted my TPS, so I'm sure it's correct according to the FSM.

I have a high idle (1800 in park) that also fluctuates rapidly upon startup.

Thanks for any advice.
 
I finally broke down and took my LC to a mechanic. He said that there was definitely an electrical issue and that he didn't have time to sort it out. Are there definite areas of suspicion? What are the common areas of the wiring harness to look for? I've read something about this in the past but can't seem to find them on the forum. Thanks for any help you can provide.
 
I hear a lot of people that get chafing on the wires that run close to the egr valve, start there, and I'd also look around your exhaust manifold to see if anything looks melted thru there. Other than that start on one side of the engine and "grid search" it inch by inch. Pain in the ass, I know, but most thorough way I know of. Good luck!
 
Vacuum leak?
 
Alleycats said:
Vacuum leak?
Click to expand...
Ben through all lines and everything is good. Also used propane around every vaccum line and connection to make sure I hadn't visually missed anything. However, it does act like a vacuum leak.

I've chased down about every known culprit that would cause my rough idle and stumble, and finally arrived at the IAC as the problem. The new one I bought didn't work, which turned me on to the fact there was no power going to it.

Now to find that problem.
 
How is your charcoal canister? I had a similar issue where my IAC would not click when I shut the engine down and I was also having pressure issues in my gas tank so just to troubleshoot I capped off the charcoal canister and vcv and viola, I had clicking on engine shut down. Not saying this is your issue exactly, just throwing out ideas.
 
Last edited:
Alleycats said:
How is your charcoal canister? I had a similar issue where my IAC would not click when I shut the engine down and I was also having pressure issues in my gas tank so just to troubleshoot I capped off the charcoal canister and vcv and viola, I had clicking on engine shut down. Not saying this is your issue exactly, just throwing out ideas.
Click to expand...
 
I checked the charcoal canister...clogged tight. It seems to run better after I bypassed it, but not great. Also noticed that my manifold was glowing after a 10 min drive at 55mph.
 
If your manifold is glowing after that little bit of work, then I would say that's leaning toward clogged catalytic converter.

Also, check your timing because too far retarded timing will be firing the charge too late and you're pushing flames out the exhaust valve and overheating the exhaust valves and manifold.

That does not see to be what your original post was about, but you don't really state what the "problem" is other than no click. Maybe I'm misunderstanding.....
 
@BILT4ME, thanks for the reply.

It all started about 6 months ago. My LC was running fine, cruising 65mph down I-40 when I had a sudden stutter and loss of power. Still ran, but very rough. I attributed it to a rust hole getting sucked through on my down pipe. I had exhaust components replaced, including cats but it didn't fix the problem. I found an o2 sensor faulty and replaced it. Later, threw a code for TPS and replaced it, adjusted per FSM. Still didn't fix the problem. I've since replaced fuel pump, fuel sock, fuel filter, all vacuum lines, intake hoses, cleaned the throttle body, wires, plugs, dist cap, rotor, fuel pressure regulator, dampener....no change. Finally narrowed it all down to my IAC. I replaced it. Still no power to it. That's where I'm at so far....

Currently it stumbles, but accelerates pretty good through 2nd and 3rd gear. When it hits 55mph, it misses and shakes. Feels like i would imagine driving a helicopter might.

Finally I took it to a mechanic figuring he might be able to go through the wiring as I haven't had time to do myself. He said there was definitely something screwy electronically but didn't have time to tinker with it.
 
@jonheld
Is it possible he slipped a tooth on his timing chain and he's running out of time? I'm not familiar enough with the 3FE to know the intricacies. However, if the computer is trying to compensate timing, dumping fuel to satisfy O2 sensors, he may be over-fueling which is causing the other issues. Since it happened suddenly, I could think it was electrical, but with the issue of the exhaust manifold turning cherry red, that indicates timing to me.

Have you checked your timing by bypassing the computer (paperclip?) and checking the base timing?

Thoughts?
 
BILT4ME said:
@jonheld
Is it possible he slipped a tooth on his timing chain and he's running out of time? I'm not familiar enough with the 3FE to know the intricacies. However, if the computer is trying to compensate timing, dumping fuel to satisfy O2 sensors, he may be over-fueling which is causing the other issues. Since it happened suddenly, I could think it was electrical, but with the issue of the exhaust manifold turning cherry red, that indicates timing to me.

Have you checked your timing by bypassing the computer (paperclip?) and checking the base timing?

Thoughts?
Click to expand...

I checked my timing a while back, but that was at the time I installed the new TPS. I later discovered was out of adjustment. I will check the timing again today and bypass the computer. I did not do that before, just adjusted it at idle.

Thanks @BILT4ME & @jonheld
 
I cannot get the idle down to 650. Still no power to the ISC. I'm going to pull the plenum this evening and check the wiring harness that runs underneath. Hopefully I'll find the culprit.
 
STICKP said:
I finally broke down and took my LC to a mechanic. He said that there was definitely an electrical issue and that he didn't have time to sort it out. Are there definite areas of suspicion? What are the common areas of the wiring harness to look for? I've read something about this in the past but can't seem to find them on the forum. Thanks for any help you can provide.
Click to expand...

Why is it that mechanics shy away from electrical issues? I mean they are going to get paid for the job! It seems to me that most "certified auto technicians" when it comes to electrical issues, tnt know much or they are afraid to deal with it...:bang:
 
jvazquez53 said:
Why is it that mechanics shy away from electrical issues? I mean they are going to get paid for the job! It seems to me that most "certified auto technicians" when it comes to electrical issues, tnt know much or they are afraid to deal with it...:bang:
Click to expand...

because a large portion are only going to get paid for what it calls in mitchell or alldata and finding an electrical problem can take hours or days and they will not get paid for the hours they actually put in then if the issue arises again and they have to warranty the work they did it could be another loss of hours trying to find if its the same point of failure or something new.
 
The 3fe has timing gears, so the chance of them skipping a tooth is really low.

However, I'm not sure if the gears themselves are held with a woodruff pin or something. I suppose there's a chance that they slipped on the shaft.

Is the stumbling RPM related, or is it continuous throughout the RPM range?
 
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