Hi guys,

I got another problem with my 1991 4Runner V6 2WD with 100K miles on it. Nobody seems to know what causes it and I don't want to take to the stealership.
Ok, truck starts good and keeps ~900-1K rms. When it warms up the rpms go down to ~800 rpm. The problem starts if I shut down the engine when it's hot for about 15-20 minutes and start it back up, the rpms go down to ~400-500 and it stays low and jumps a little. When it happens the engine shakes a bit.
The same problem also appears when I drive in traffic. The rpms seem to go slowly, ~100rmps every time I stop, until it goes down to 600 rpms. And then it just keep it at 600.
After that, if I drive it for a while without stopping, the rmps go back to normal.

It seems like something gets too hot and doesn't do its job!!!


Guys, you are my last hope before I'll start giving my $$$ away to the stealership.

 

That doesn't sound like that big of a problem, mine does that all the time. Recently it's even idled roughly it's been so low. You might just want to clean the throttle body, run some injector cleaner, basically do a tune up.

 

but why does it do it ONLY when the rig is hot???

 

This is only a guess but the same thing happened to my g/f's Accord. After it warmed up, the idle would drop so low that it would vibrate.
It was a simple idle adjustment by the mechanic. You can adjust the idle with a screwdriver.

I'm not familar with the older 4Runners but it doesn't sound serious at all and I think Robinhood is correct, just a tuneup. Maybe the idle is linked to theromostat and is just mis-adjusted and drops the idle too low.

 

Nope, tried it and it didn't help much. COuld a fuel pump, egr valve, pcv valve, module, or AFM cause this problem?? I trying to pin point it without having to spend LOTS of $ on replacing parts that are good.

 

Oh yeah, almost forgot...I changed the plugs (I installed the Toyota originals) 2K miles ago and I've done the whole tune up 15K miles ago (got all the parts from AutoZone).

 

This happened in my 94. The dealership claimed I needed an Injector Rebuild. The tech said this was leaky injectors. Well, not being one to give a stealership 500 bucks, I did an agressive treatment of injector cleaners. From what I gather from this board the 3.0's injectors get gunked up. Also you may try a "Motor Vac" if you can find a shop in your area that has this machine. People get good results from this but its not free. Or, if you can be without your truck for a while and have the ability to, take out your injectors and get them ultra sonicly cleaned and balanced, get some new gaskets and to the rebuild youself.

 

I hate to say this, because I don't want to scare you, but that problem is also a symptom of a leaking headgasket... The problem occurs because when the engine heats up and then is left to sit for a while, there are some fluids from the coolant system that have leaked into one or more combustion chambers and it takes a few minutes for the excess coolant to burn off and the headgasket to expand again, sealing the leak.

You might want to have the cooling system pressure tested to check for that. Talk to a mechanic who is intimately familiar with the 3.0, even if it means talking to a dealer. There are some good ones out there.

Hope this helps.
G

 

When this first happened the head gasket was the first thing I thought. It was one of my first posts on the board. Here I did have a compression test with spark plug change and that came back fine. I never had the cooling system checked but it did try to over heat going over the mountains. Mabey I did have a head issue.

 

Mossback, that could very well be your problem, as that is another symptom of a leaking headgasket...

G

 

When was the oxygen sensor last replaced?

 

[QUOTE=Dr. Zhivago]I hate to say this, because I don't want to scare you, but that problem is also a symptom of a leaking headgasket... G/QUOTE]

This was the very first symptom I had of a leaking head gasket. I din't realize what it was at the time, but that was the root cause. Call Toyota...maybe you're still covered for the replacement. If you are, drive it like you STOLE, and get a new long block. If you're not covered, it's a sad thing...$$$$$$$$

 

[QUOTE=Blair]I've done the head gasket recall 2 months (1500 miles) ago. I've had the problem before the recall and I still have it now.

And I have not changed the O2 sensor.

 

Hearing this would then make me lean in the direction of the 02 sensor. I'm thinking that the symptom shows up because the 02 sensor gets fouled by the coolant in the exhaust stream. Did they change your 02 sensor?

All these symptoms went away for me...and then I rolled the runner!

 

Nope, they didn't. Could it get too hot when and cause the problem?

 

Have you set the base idle? A bad Idle air control valve can cause stuff like that to happen too. Something to check.

John

 

Not positive, but I think it can get fouled in the exhaust stream. More learned members will be sure to chime in through out the day.

 

I'd say replace the fuel filter and oxygen sensor and check the idle air control valve and throttle body. I'm not too familiar with the 3.0's but I've had the same problems with an old car of mine and currently my girlfriend's. Her's even cut off quite a bit. After the above maintenance it runs fine now.

 

I'd vote O2 Sensor or TPS

Fink

 

My friend had a problem on his v6 with the idle going up and down,.He had two things wrong: Egr sticking and TPS was set wrong.