Idling and acceleration problems

perk · 03-20-07, 08:55 PM

Update... cables and tps ok, not the problem. I have a new, recommended mechanic on the case. Initially he cleaned the MAF, found it to be running well, no codes etc. and gave it back. It acted up again (idling low), I took it back, he then noticed that the ground terminal on the battery was very loose. It's been like this for some time, I just never realized it was a problem (the terminal was not able to be tightened down anymore). He explained that a host of problems can result from this and perhaps this is the problem. He put a new connector on (free of charge) and sent me on my way. Drove home, running great, in fact it felt even peppier, no problems, fingers crossed, feeling hopeful.

As if it could be that simple. This morning on the way to drop my daughter off at school, it begins stumbling at low speed, shaking, running rough, bogging down. Check engine light comes on (first time in this entire saga). Take it back to mechanic, hooks up to computer, reads cylinder 4 misfire. I take it home change spark plug #4 (it's very black). It continues misfiring on my way back to the mechanic. He pulls the plug, checks compression (175), checks spark.

He decides he needs to consult some sort of Toyota Mechanics Hotline that he has membership to, and do further investigation. He mentioned wanting to find out how the #4 fuel injector is behaving. He says he wants to rule out at least one other thing before thinking the problem lies with the computer. For some reason, he didn't want to share his speculation about what the other thing is. This has become quite the mystery. I'll post back when there is a change. I'm taking it back in next Monday.

Perk

RavenTai · 03-21-07, 04:28 AM

harness.

perk · 03-21-07, 08:44 AM

I know the likely spots for a problem are behind the glove box, next to the EGR pipe, and where it enters into the cabin on the firewall. I've looked at all three spots before and there are no signs of damage on the outside. Could there still be a problem with the wires on the inside with no signs of damage on the outside? If so, whats the best way to go about isolating and repairing the problem wire(s)?

Thanks
Perk

Beowulf · 03-21-07, 08:55 AM

Quote:

Originally Posted by perk

Could there still be a problem with the wires on the inside with no signs of damage on the outside?

Perk,
Yes, there could be damage on the inside with no external visible signs. The problem with shorted/broken wires by the EGR valve is a VERY common issue with the symptoms that you describe. Read this thread.

His pictures are crappy but you'll get the idea.

Please keep updating this thread and let us know how this finally gets resolved. Seems we are having a rash of members reporting very similar symptoms as yours. There was another member 2 or 3 years ago, that had a dealer trouble-shoot the problem and they isolated a bad injector (or that's what they told him.) It is possible that your #5 injector has gone tits-up. Details in this thread.

-B-

perk · 03-21-07, 09:41 AM

Thanks Beo
Part of me wants to go open up the wiring harness and check out the wires, but I think I'll wait until Monday for the mechanic to pursue his avenues. I know he wants to make sure there is nothing wrong with the injector first. I will make sure he is aware of the likelihood for problems with the harness. I just wish I didn't have to wait until Monday to see what he comes up with.

I'll update when theres more info,
Perk

Nemo · 03-21-07, 09:58 AM

Perk,
I started having these problems with my TPS. Replaced it to no avail. Tested every test from the FSM and it kept pointing to the Harness and / or ECM. I actually borrowed a spare ECM from Slee and no change in behavior. My symptoms were a little off from what you are experiencing, but I found that the IDL connection between the ECM and the TPS was compromised. I actually spliced a new wire in to go around the problem and fixed the issue. Since then I have seen a problem with Lean Conditions and pointing me to the O2 Sensors. Checked them and the same sort of issues. I ordered a new harness and will be placing it in with a bunch of protective heat tape et cetera. Not saying yours is this, but it was my problem and I wasn't comfortable with my soldering skills and all the new wires running everywhere out of the wiring harness. In any case if I run into a ground wire it would have been a b(*ch if you know what I mean. Worth a look. BTW. The only thing that didn't check out for me was the one test for Pin 1 and Pin 2 of the TPS that should have been showing ~9V to ~14V. I was getting somewhere around 1.3V. I finally listened to the FSM and started testing with the wires and got it to work. So far so good with my home fixes, but this weekend I will be putting in the new wiring harness. Fun stuff but I don't want to worry everytime I get a check engine light whether it is the wiring or actually problem with my mechanicals.

Beowulf · 03-21-07, 10:07 AM

Quote:

Originally Posted by Nemo

... but I found that the IDL connection between the ECM and the TPS was compromised.

Nemo,
Can you be more specific? Are you saying that you suspect a wiring problem in the main engine wiring harness and that you "fixed" the problem by cutting a specific wire (to the TPS) at the ECM and ran a completely new wire to the TPS?

Do you have pics of this repair?

-B-

perk · 03-21-07, 10:07 AM

Good luck replacing the wiring harness Nemo. Looking forward to hearing about your experience.

Nemo · 03-21-07, 10:12 AM

No pics of the fix but yes, I cut out the IDL wire and ran a new one through the FW to the TPS and basically wrapped it up in the flex hose and done and done. I obviously had to cut out the Cruise Control for now, but I figured I was on my way of replacing the whole Engine Harness anyways. Make sure if you try these things to go over the Wiring Diagram 10 times before cutting wires and splicing in. Like I said cutting my wire required me pulling the harness to the Cruise Control ECU. So far so good.

perk · 03-28-07, 11:26 PM

It was the harness. The wires up against the EGR pipe were burnt; two running to cylinder 4 and two running to the IAC. The IAC wires explain the wacky idle. My mechanic repalced approximately 2 inch sections of these wires and wrapped it all back up with header tape. He said the rest of the wires looked fine, the burnt ones were the only ones directly against the pipe. He returned them to me and all four are burnt down to the copper. Two days of driving including an 80 mile freeway trip and it's running great, idling right at 6-700. I just looked at my original post and realized it's been over a year and a half since the symptoms first appeared.

It seems like this issue is going to affect many 80 owners. Perhaps it's affecting many currently who don't know it. Wrapping the harness in this area would be good preventative maintanence before problems arise and it has to be cut into and repaired.

This leads to the question, why is this happening to some and not others? Everyone's harness is against the EGR pipe. Aren't all engines running at approximately the same temp, assuming a healthy cooling system? I've never had an overheating problem, I replaced thermostat, fan clutch and radiator (to brass) as prevention. Aren't all harnesses prepared the same at the factory? Is it something that causes the EGR pipe to get extra hot? Definetely seems like this is becoming FAQ material.

Thanks again to all whove assissted in this saga,
Perk

Beowulf · 03-29-07, 08:21 AM

Quote:

Originally Posted by perk

It seems like this issue is going to affect many 80 owners. Perhaps it's affecting many currently who don't know it. Wrapping the harness in this area would be good preventative maintanence before problems arise and it has to be cut into and repaired.

Is it something that causes the EGR pipe to get extra hot? Definetely seems like this is becoming FAQ material.

Perk,
All 1FZ-FE equipped 80s are candidates for problems with the engine wiring harness. This problem was identified many years ago; at least 6 years ago that I know of. It has been suggested many times for new owners to wrap this area with heat tape as part of their base-lining.

The EGR pipe will get hotter on extended trips. As you point out, if this has not been added to the FAQ then it should be. Both the PM, the problem identification, and the problem resolution. Can you confirm that this is NOT in the FAQ?

-B-

fj40fax · 03-29-07, 08:50 AM

Maybe some people's clips don't break and therefore keep the harness farther away from the EGR. I know mine was broken.

Fax

fj40fax · 03-29-07, 08:57 AM

When mine got fixed it got zip tied about 2" away from the EGR. I think that distance and a good thick layer of header wrap wrapped in heat tape should make this a long term fix.

knorrena · 03-29-07, 09:52 AM

For the most part I can follow this discussion, but I am having trouble orienting myself with the various harnesses and their locations. I realize that this is due to my nube status and my consequent lack of familiarity with my truck. Are the harnesses that are subject to heat damage obvious, in other words, can I just pop the hood and discern which harnesses should be protected? Can someone recommend a heat tape?

Karl

Beowulf · 03-31-07, 08:00 AM

Knorrena,

Heat tape is available from your local ricer shop or speed shop. Online at Jegs or Summit Racing.

The location of the harness is shown in post #64. You can use the large nut in the upper right portion of the picture for a landmark. That is the nut on the EGR valve which was removed in that picture. The general location is along the firewall in the center. You will see some heater hoses and the heater valve. Right under that is the EGR valve and right next to that is the main engine wiring harness.

Let me know if you need more help finding this harness.

-B-

bpenn1980 · 11-29-07, 03:34 PM

Quote:

Originally Posted by Beowulf

Perk,
All 1FZ-FE equipped 80s are candidates for problems with the engine wiring harness. This problem was identified many years ago; at least 6 years ago that I know of. It has been suggested many times for new owners to wrap this area with heat tape as part of their base-lining.

The EGR pipe will get hotter on extended trips. As you point out, if this has not been added to the FAQ then it should be. Both the PM, the problem identification, and the problem resolution. Can you confirm that this is NOT in the FAQ?

-B-

Just picked up my fzj-80 last week and am having some similar issues to those discussed in this thread. Start up idle at 1,800-2,000 rpm, slowly comes down to 800'ish rpm over a couple minutes of warming up, idles after reaching operating temp in Drive at stops at 600 rpm (feels smooth), but sometimes idles very rough at 400 rpm or just under and feels like it could stall but doesnt.... I'll isolate the harness from the EGR and add some insulation, but I suspect the damage is probably already done. We'll see

ps- I couldnt easily find this thread and/or fix in the FAQ so I dont know if its been added. From my searches on "low idle", "rough idle", "IAC", etc it seems this is a recurring issue that should be in FAQ if it isnt already

franku · 12-02-07, 08:43 AM

I would replace the fuel pump relay...

pmccumber · 06-13-09, 12:12 PM

Since this is a thread about the source of nasty idles. I had one recently and it is now perfect.

The source of the problem was one of the pins on the IAC connector was bent over. Didn't throw any codes. It would "figure itself out" every other day and run good for a while. The other piece of wisdom that is probably all over this site but is worth repeating is that pulling the EFI fuse for 15 minutes or so clears all the bad stuff it had learned. Furthermore, a very good source told me that this is actually something to try if your rig is ever running badly as it will force the factory settings upon the controller.

Oh, I'm pretty sure the pin got bent during a valve service. I'm really happy with how it is running now.

Paul