91 3FE - No power to ISC

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Jdayment hit it right on the head! When I help out my bro-in-law at his shop (after all the wanna-be mechanics get mad and quit) I only get paid what "the book" calls for on labor. So, on his 80, if I'm working on the IAC and the book calls .5 for replacement...... I get .5, whether it takes me 5 minutes.. or 5 hours I'm still only getting .5 credit. Anyone knows chasing electrical "gremlins" eats hours up quick. So you can see why "shop" mechanics run when a job like that shows up! Now, we would tell the customer if they could leave the vehicle for a week or so, we would work on it during slow times, and that way we could get them out with a little more $$ in their pockets!! End of book! Lol
 
jdayment said:
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
STICKP said:
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
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Those 3FE are bulletproof. No timing chain; it has gears and never heard of one losing a woodruff key.
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This is true. After all, I've been trailing this problem for weeks now. However, I had a breakthrough today. Where the wiring harness is routed under the plenum, I found that it was burned through at the air intake manifold. When I say burned through, I mean completely fried, wire insulation and all. I'll be working to fix the problem this weekend. I will post pics for future victims. Just glad I found the problem!
 
Here are 2 pics from this weekend. You can see how extensive the burn through is. I'm still working on getting everything reconnected. The only wire on my ISC that wasn't burned through was 1 12v wire. 3 of the TPS wires were completely burned through, along with another from the coolant temperature sensor.

LC.webp


LCII.webp
 
STICKP said:
Here are 2 pics from this weekend. You can see how extensive the burn through is. I'm still working on getting everything reconnected. The only wire on my ISC that wasn't burned through was 1 12v wire. 3 of the TPS wires were completely burned through, along with another from the coolant temperature sensor.

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Wow....that's scary..... I'd hate to try a "trail fix" on that!
 
Marine7 said:
Wow....that's scary..... I'd hate to try a "trail fix" on that!
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I'm amazed that I was still able to drive it around at all. It looks like the previous owner had messed with the wiring at some point...lots of electrical tape and barely legitimate connectors. I'm thinking that when he replaced the plenum, he didn't route the harness around the upright bracket that supports the plenum. This would have kept the harness away from the heat source.
 
Man, my 91 literally just did this exac5 thing a couple weeks ago and have been chasing it myself. Even has the same codes. The only difference is mine acted up a couple times a few months ago at a stop light and sorted itself before I got home. Did it a couple days later for a few minutes and then sorted itself once again. Wend a couple months and BAM! Now its hardcore all the time lol. Ill be checking this out next before I go wasting more time.
 
@kickfli12 - Definitely check it out. I chased so many problems that were at first intermittent and then constant. What I think was happening is the wires were getting super hot and really hard but not quite burned through, then I guess, the hotter they became, they eventually burned totally through. I could have saved myself a lot of money and sweat had I looked there first. I will add, that with the plenum on, it wasn't clear that any wires were burned through, so it's definitely worth taking the plenum chamber off and checking the wiring harness good.
 
So i got home from work and looked in there. Toward the firewall it looks like the previous owner had already been down that road. Looks like theyve sorted it correctly too. Even used heatshrink. Cranked it up and it ran awful like it has been. Shook the hell out of the harness to see if anything would change. Nothing. Startes to poke around some more. Cleaned the contacts on temp sensors and whatnot. Some were corroded and the wires were stiff. Still ran like crap. Tapped on my efi relay cause before if you did this the truck would try to die and I had just replaced it with a new one from toyota. The truck tried to die like the original and then started to run alright again.... I guess ill have to tear the fuse box apart and replace the terminals and see if its a contact issue. I doubt it is cause I can wiggle the hell out of it and it didnt help the running rough issue.
 
Sorry to jack your thread but I'm pretty sure ive got the same thing going on as you. As I said in my last post the truck started to run alright again. Decided I would go on a test drive to the gas station to put some gas in it and about 5 seconds after I crossed the railroad tracks it started to run really bad again. Limped it home and pulled codes 41 and 51. I replaced the tps last week after having these codes previously as well as code 28. And the tps wires run right through where our harnesses were fried so tomorrow I'm going to tear into it to see what I find. Thanks again for the photos and the info
 
Well @kickfli2 did you find your problem?

And @STICKP did replacing the fried section of harness solve all of your issues?
 
catfishhands said:
Well @kickfli2 did you find your problem?

And @STICKP did replacing the fried section of harness solve all of your issues?
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@catfishhands - Solved everything. In fact, the truck runs better than it ever has. I suspect this was a longstanding problem that kept getting increasingly worse until vital engine managment components were starting to fail. I cut the harness open, snipped out all of the hard sections (one at a time) and using connectors, added in a new section of wire. It fired up and purred like a champ.
 
@catfishhands yeah, sort of. I had other issues that needed to be addressed afterwards cause I'm sure all that fried harness killed a lot of my sensors.
 
Looks like it maybe time for me to do the same. Truck would just shut off while driving, would need to sit for at least an hour before it would restart. I replaced the EFI relay this past weekend. Started right up and sounded and felt like it was running much better with a brief ride around the block. I went to get in it today to take it up to the store and it would not start and actually started to backfire into the air cleaner box with noticeable smoke and exhaust odor. It will turn over, fire for a second after a couple tries and stall immediately with what sounds like a backfire into the breather. I am at a loss over this one. When turning key on all lights on dash come on, etc.
 
kickfli12 said:
Sorry to jack your thread but I'm pretty sure ive got the same thing going on as you. As I said in my last post the truck started to run alright again. Decided I would go on a test drive to the gas station to put some gas in it and about 5 seconds after I crossed the railroad tracks it started to run really bad again. Limped it home and pulled codes 41 and 51. I replaced the tps last week after having these codes previously as well as code 28. And the tps wires run right through where our harnesses were fried so tomorrow I'm going to tear into it to see what I find. Thanks again for the photos and the info
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Did you replace your efi relay with the plastic Camry one yet? Part number is 28300-16010. Here’s a link

28300-16010 Genuine Toyota Relay Assembly, Starter

ToyotaPartsDeal.com offers the great deal for genuine Toyota parts 28300-16010 (2830016010) Relay Assembly, Starter. All parts are backed by the Toyota's warranty.
www.toyotapartsdeal.com www.toyotapartsdeal.com

Definitely look around for better deals, but this was such an amazing improvement to my ride. My metal relay would get so hot I couldn’t even take it out after driving. If I shut the car off, it wouldn’t start for 15 minutes until it cooled down. Haven’t had a problem since swapping to this one. I believe Jonheld is the mastermind of that change.
 
Navyator said:
Did you replace your efi relay with the plastic Camry one yet? Part number is 28300-16010. Here’s a link

28300-16010 Genuine Toyota Relay Assembly, Starter

ToyotaPartsDeal.com offers the great deal for genuine Toyota parts 28300-16010 (2830016010) Relay Assembly, Starter. All parts are backed by the Toyota's warranty.
www.toyotapartsdeal.com www.toyotapartsdeal.com

Definitely look around for better deals, but this was such an amazing improvement to my ride. My metal relay would get so hot I couldn’t even take it out after driving. If I shut the car off, it wouldn’t start for 15 minutes until it cooled down. Haven’t had a problem since swapping to this one. I believe Jonheld is the mastermind of that change.
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Your saying this starter relay could be the culprit with the issues I am having with my 1992 FJ80?
 
ToyoFJ80 said:
Your saying this starter relay could be the culprit with the issues I am having with my 1992 FJ80?
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I was responding to kickfli12 because he specifically talked about tapping his efi relay. I figured before he replaces the terminal he should try getting the better relay. I’m not an expert on electrical systems, but the guy who just commented, jonheld, is. Definitely heed his advice if he lends it, i was able to get through some issues with his written guide. Hope you can resolve your issues!
 
Jumped in my 1992 and fired right up this morning! Yeah!!!!! Ran on high idle due to it being cold and shut down like someone turned the key off. Check engine light was on, would not start afterwards. I believe there is some sort of electrical gremlins in this thing!!!!
 
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