Misfire, Shuddering/shaking, lopey idle... (1 Viewer)

[BlueCruiser84]

Riad,

Thanks for the link. It ended up leading me to a bunch of other useful links. I am hopeful that the wiring harness is going to be my issue.

 

[BlueCruiser84]

Update..

I dug into the harness at the fiewall and whaddya know; two wires were melted through the insulation and two others were starting. I patched up the wires and wrapped the harness back up with electrical tape.

What are people wrapping the harness with before they button everything back up? is it anything special or is it just header wrap and aluminum tape? Anyone got a link?

 

[Dave 2000]

Update..

I dug into the harness at the fiewall and whaddya know; two wires were melted through the insulation and two others were starting. I patched up the wires and wrapped the harness back up with electrical tape.

What are people wrapping the harness with before they button everything back up? is it anything special or is it just header wrap and aluminum tape? Anyone got a link?

Great you found something but is it running better?

regards

Dave

 

[BlueCruiser84]

Great you found something but is it running better?

regards

Dave

Haven't got it all back together yet. Napa wasn't open over the weekend, but I ordered the heat wrap today and I am about to go pick it up.

Hopefully I can get the thing buttoned up tonight and then to the moment of truth.

Brian

 

[Dave 2000]

Fingers crossed mate, but as I am off to bed now I will 'check in' tommorow morning

regards

Dave

 

[BlueCruiser84]

Got it all buttoned back up. Threw in a new valve cover gasket and spark plug donuts because I was right there, and I disabled the EGR so there is not a chance of ruining my rehab'd wiring harness.

I wrapped the harness in electrical tape, then header wrap, then tape, then hose clamped an extra piece of the header wrap to the side of the harness where it will be resting against the EGR valve. I then disabled the EGR... you can never be too careful. Since mine is a '93 and it still has the factory jumper in the ECU side of the EGR temp sensor (and doesn't even have an EGR temp sensor) I didn't have to do anything there.

Started her up and she ran like a champ. Nice smooth idle, granted the computer was still figuring some stuff out, but otherwise she idled great. I haven't taken her for a drive yet, but I will report back when I do.

 

[Dave 2000]

Way to go! Good to see your back on the road again, give yourself a pat on the back and buy a 6 pack from the money you saved by not going to a garage.

regards


Dave

 

[kidglove13]

Nice work Glad you got it fixed

 

[S.CarolinaFZJ80]

Which two wires were toast?

 

[BlueCruiser84]

Well on the harness it was two of the injector wires. I think a yellow-green (a little bit melted) and a white-red (a lotta bit melted)... I can't remember for sure. All the injector wires run right by that EGR pipe on the outside of the harness bundle... it just kind of depends how they were wrapped.

the ones behind the glove box were easy to check and back there I had a white-red wire that was totally severed - not sure how that happened, and a blue-white wire that was very frayed. The wiring diagram shows clearly which wire is for which injector. If you are having issues and can narrow it down to an injector I would check behind the glovebox first.

If the glovebox checks out ok and you are still having intermittent misfires, or in my case just a misfire you should check the wiring harness by the back of the valve cover. The bad part is that you (well I did anyways) have to remove the throttle body, EGR, the valve cover, and some of the injector clips (which all broke) to really get the harness out where you can work on it. Even then it is a pain especially if you have a lifted truck. On the plus side you can do some good maintenance items while you are in there.

Let me know if you have any other questions.

 

[MARKTLC80]

My experience with this kind of shaking, miss fire was blown head gasket on first cylinder but like I said it was my experience. It would not hurt to do pressure test since the sparks will be out anyway. Good luck

 

[BlueCruiser84]

Ok, how about an update...?

It is back. After I "fixed" the problem I took it for a spin and after about 5 miles it smoothed out, idled great, ran really well in general. I got it home and parked it. Next couple times I drove it it would always start up a little rough and then once it warmed up would run really well. Now it just misses/misfires, though not as badly as it did the first time.

Again, no check engine light, no milky oil, no bubbles in coolant, no white smoke... no signs of a headgasket failure.

I think I've read somewhere on hear about a coolant temperature sensor causing issues like that? what about the fuel pressure regulator. The one on the truck looks like someone has beat on it in the past. Maybe it was having issues?

 

[BlueCruiser84]

What about the fuel pump relay going out on the low side? If I rev and hole the gas at higher RPMS, say >1500 it smooths out considerably. If I then release my foot from the pedal the rpms drop normally but continue down passed idle until the motor stumbles a couple times and dies. It will start back up fine.

 

[Kernal]

Could you have a new problem (?vacuum leak) after working on the valve cover and throttle body??

 

[bpenn1980]

What about the fuel pump relay going out on the low side? If I rev and hole the gas at higher RPMS, say >1500 it smooths out considerably. If I then release my foot from the pedal the rpms drop normally but continue down passed idle until the motor stumbles a couple times and dies. It will start back up fine.

Per the FSM the only misfire/rough idle/stall after accelerator pedal depressed matches are:

Volume Air Flow Circuit
Injectors
ECM
Spark Plug
EGR

The EGR is ranking pretty high in priority per the FSM across all 3 symptoms. How did you disable the EGR system?

Fuel Lines and Fuel Pressure Regulator do also line up with rough idle and stall after acceleration. It seems you need sst 09268-45012 in order to check fuel pressure. There's no test for the regulator on its own according to the fsm...[edit: if pressure is high, replace fpr seems to be the test. If low, check fuel hoses, fuel pump, fuel filter, fuel pump relay, fuel pump resistor, injectors]

Are you sure you found any and all damaged wires while you were in there?

Sucks man, hope you get it sorted.

 

[BlueCruiser84]

Could you have a new problem (?vacuum leak) after working on the valve cover and throttle body??

That is very possible. Could be coincidence that is shows similar symptoms. I did a cursory check of the stuff I removed and it all looked right. That doesn't mean I didn't crack something or bend a connector just right etc.

Per the FSM the only misfire/rough idle/stall after accelerator pedal depressed matches are:

Volume Air Flow Circuit
Injectors
ECM
Spark Plug
EGR

The EGR is ranking pretty high in priority per the FSM across all 3 symptoms. How did you disable the EGR system?

Fuel Lines and Fuel Pressure Regulator do also line up with rough idle and stall after acceleration. It seems you need sst 09268-45012 in order to check fuel pressure. There's no test for the regulator on its own according to the fsm...[edit: if pressure is high, replace fpr seems to be the test. If low, check fuel hoses, fuel pump, fuel filter, fuel pump relay, fuel pump resistor, injectors]

Are you sure you found any and all damaged wires while you were in there?

Sucks man, hope you get it sorted.

To disable the EGR I removed the modulator and plugged all the lines. After the first 20 minute drive I could put my hand on the pipe, so I am pretty sure it worked. I don't have a temp sensor so I just left the factory jumper in the ECU end of the plug.

I think a check of the fuel pressure might be a good thing. At least I can rule it out.

As for the wires, I went over them about 4 times because I really did not want to go back in there, but I still could have missed one... though I doubt it (unless it is in another area).

 

[BlueCruiser84]

Drove it around for for about 30 minutes today after making sure everything was tight... the intake tube was loose. Smoothed out the idle for about a minute, but then it went right back to its old ways.

Things I noticed on the drive:

-It runs great at WOT.

-Power braking in forward and reverse nets the same amount of missing.

-Sitting in the driveway in park if I rev it very slowly it will miss all the way up to about 1800 RPMs and then usually it smooths out and pulls the rest of the way very nicely. If I let my foot off the throttle it will drop back to around 1000 RPMs and run s***ty. Sometimes, though, it will stay running smoothly.

I am starting to get annoyed because I am sure it is one of the 20 sensors that are in hard to reach places. I miss working on a carburetor with 2 wires...

 

[ajax1]

cold temp sensor went out on my wifes 4runner it ran pretty s***ty through all rpms and speeds would miss when you gave it good amount of pedal and threw check engine

 

[BlueCruiser84]

I am starting to get a bit irritated at this thing... I replaced the coolant temperature sensor (ECT) and it had no affect.

The thing that bothers me is that it has a "perfect" idle but it chugs... does that make sense? It will idle all day with no fluctuations but it sounds like it is missing on every other stroke. Kind of a glug glug, glug, glug, glug at about 600 rpms.

It is a bit underpowered. I know this because every now and then when I am driving it will perk up and run great. And it is a little rough on initial acceleration, but once it gets up above 1500 it is almost not noticeable.

The exhaust still smells pretty gassey and there are still no headgasket symptoms.

Could the TPS or the IAC be doing this to me? I know that '93 are notorious for having bad ECMs, but most things I have read sound nothing like this. I will admit that I am reluctant to get out my multimeter and start probing things.

What about oxygen sensors?

Any help fellers? I am running out of things to check.

 

[Dave 2000]

Have you done a dynamic compression check? I am not thinking head gasket but more a sticky or leaking valve, both would be very noticable at idle but would be hidden at higher engine revs.

regards


Dave