92 runner that i cant diagnose!

[keganthewhale]

Alright gents, I'm lost and don't know how to fix it!

I have a 92, 3.slow runner that I picked up recently for cheap and the guy couldn't figure out what was wrong with it and couldn't afford to put more time into it (it was an actual repair shop and they weren't going to get their money out of it if they fixed it).

Now I already have a 95 runner that was on it's last limb so I have one to pull parts from and have quite a few times so far. When I got the vehicle the guy wanted to "isolate" the issue to try and diagnose it and in the process pulled almost all of the vacuum lines, the EGR valve, most of the air box, and unplugged several wires under the hood. So since I bought it I have replaced the power steering pump, the alternator, the battery, the fuel pump and filter, the mass air flow sensor, the EGR valve, the ECU, and have (to the best of my knowledge and picture reading abilities) replaces all the vacuum lines that he removed. Mind you there were reasons behind replacing all of those parts, I wasn't just throwing parts at it.

What do you know?! it starts! and it drives awesome!
here comes the problem, once its warmed up and after its been shut off for a few minutes then you start it back up it runs like crap!
-it barely holds 250 rpm
-will often die if you rev it up and then remove your foot from the gas (even while driving if coming up to a stop)
-feels like its bogging when you try to accelerate
-has a very difficult time getting above 2500 rpm
- if you are going down the road at 2500 rpm and try to accelerate instead of increasing rpm and accelerating, it drops about 250-500 rpm's and accelerates very slowly

Leave it for about 4 hours, let the engine cool down, come back and start it up and it runs just like it should again... and this is a consistent problem it has gone on for about 3 weeks now and I honestly have no idea how to go about fixing it and the only code that it gives is #12: engine speed sensor circuit.

Have any of you experienced something like this before? Any idea where to start so I can diagnose it correctly and go about fixing the problem?

Any help is greatly appreciated!

-Kegan

 

[giro]

I've had one or two times where my v6 hasn't performed right after a hot restart, but it's only been when it's really hot, and only that time or two.

The FSM has a "difficult to start in hot" section for engine mechanical - troubleshooting. My '92 manuals have it on page EM-81, but with the downloadable ones (see the top of the classics section) I think the closest is for a '93, so the page number might be different.

On a different car the fuel system sometimes had trouble with a hot restart due to vapor lock, but it had a 2 step fuel pump. By overriding the relay so that the pump always went at full, it fixed it. But on a similar idea, some places to look might be at a fuel pump that is starting to fail, or a fuel filter that is somewhat clogged.

The FSM says to look at the water temp sensor circuit, fuel quality, idle speed control valve, or the fuel pressure control system. It then has another 7 things. The nice thing with their troubleshooting is that they steer you towards the most likely culprit first.

Good luck

 

[KidVermicious]

That sure sounds like a fuel issue. You said you replaced the pump and filter, did you pull those off the other truck or are they new parts?

I also wonder about the TPS.

 

[keganthewhale]

The fuel pump and filter I replaced were both new and if you undo one of the bolts at the end of the fuel rail and put the key in the "on" position it will pump gas out like there is no tomorrow, so I'm sure that its at least getting to the injectors.

The only parts that were from the other runner was the power steering pump (and the diaphragm that the vacuum lines go to, it had ruptured or something and was sucking power steering fluid into the air intake, talk about clouds of white smoke and guzzling fluid...), the alternator, the EGR, and the ECU (the guy pulled the other one apart to see if had gotten wet or something and it wont run on its own ECU).
The MAS, fuel pump, fuel filter, and battery are all new.

The only reason that it being fuel issue doesn't make sense to me is that when it starts cold it runs perfect every time and stays that way as long as it isn't turned off. If I turn it off for 30 seconds and try to start it again it goes back to those symptoms. Wait 4+ hours and it'll start like new again.

 

[KidVermicious]

The only reason that it being fuel issue doesn't make sense to me is that when it starts cold it runs perfect every time and stays that way as long as it isn't turned off. If I turn it off for 30 seconds and try to start it again it goes back to those symptoms. Wait 4+ hours and it'll start like new again.

Yah, that's weird. Fuel and electrical issues are the ones that always kick my butt, mostly because I don't understand exactly what's going on in there.

So if you're stumped, drop back and punt. Test out the TPS because a flaky TPS can cause all sorts of funky issues that you wouldn't think it would be involved in, bypass the Circuit Open Relay and see if that makes things better, find the ground for the injectors and make sure it's terminated well. Um, what else, is there a vacuum line on the fuel pressure regulator? Check that, maybe heat is causing a vacuum leak there. Maybe the FPS itself gets sticky? Definitely run down the list of things the FSM says to check that Giro posted.

Not saying any of those are the trouble for sure, just throwing out ideas. Good luck!

 

[nicnmike]

Have you replaced the coil? I know on older cars, a bad coil often made starting hard when hot.

 

[giro]

The FSM has a "difficult to start in hot" section for engine mechanical - troubleshooting. My '92 manuals have it on page EM-81, but with the downloadable ones (see the top of the classics section) I think the closest is for a '93, so the page number might be different.

The FSM says to look at the
water temp sensor circuit
fuel quality
idle speed control valve
fuel pressure control system. It then has another 7 things

Ok, the next 7 things, all in order:
Intake air temp sensor circuit
cold start system (hmmm, strange, but maybe from activating when not)
Fuel pressure regulator
fuel pump
fuel lines
injectors
engine and ECT ECU

That was all for "Difficult to start in hot", but your problem is not just starting but running. See the page, and try to find something that fits.

One trick that I learned after being stuck with a different car is that you can unplug something like the MAF to have the ECU just use defaults instead of using values from the sensors. If one of your sensors is really screwed up, then once the engine is warmed up it will use that bad data. For an already hot engine, it would use the data right from the start.

I don't know why that would then cause bad drivability, since the same issues should have happened once you were warmed up. Somehow you're getting into a bad loop. But pulling the MAF connection might then let you know if it's actually stuck in something bad, or if it's sensor driven bad loop.

(on that other car, a twin turbo 3000gt, the air ducting after the MAF came apart after downshifting. Like that, once warmed, it would blow white smoke out the exhaust, and barely stay running. But unplug the MAF, and it ran decently. This was known as the "limp home" mode, and those cars aren't anywhere as reliable as a 4runner, so it was more common. Very fast car(0-60 in 4.2!!!), but it had a problem with a cylinder (horrendous sound sometimes), and when the head gasket went from a small leak to a big one, I decided to sell it. I wish I still had it, but we barely drive our two cars, and I'm sure it would be like the Alfa Romeo my dad had for a while, that it takes much more repair and servicing than it really should...at least in comparison to fairly reliable vehicles)

 

[keganthewhale]

So it's now giving code 12 and 73 (failed egr) and I was told to swap the vacuum line on the egr and that should solve the problem, but it didn't! And I had another guy say that it might be a clogged catalytic converter and to unbolt it and try to start it hot and see if that fixes it, does that sound feasible?