I've got a rough idle when it is hot outside after driving it around a while in town. Today it really got rough. No diagnostic code. No check engine light. I reset the ECU by pulling the EFI fuse and it started running good again. Could this be my ECU is going bad? I can't figure it out. It's a 1990 V6 4runner.

 

bump. Has anybody seen a problem like this?

 

I've had a hot re-start rough idle forever it seems on the 3.0L. It happens just after starting a hot engine that's been soaking in the heat. Driving normally or reving it for a bit makes it go away. Is this similar to what you have going on?

 

Exactly as you described! The other day was worse than usual. I noticed it was also running rich so I adjusted that and reset the ECU. Today was a hot day and it ran a lot better but I can still tell it wants to act up a little. I started noticing this at least last summer if not before.

 

I should add that, when it happens, there is no visible smoke whatsoever coming from the tailpipe. I'm inclined to think it's a temporary vacuum leak from somewhere or a sticking vacuum valve.

 

I've noticed a lot of pressure in the gas tank. I don't make the cap air tight and the problem vanishes. But since I posted the problem I really hadn't seen much hot weather lately. I'm going to try and figure it out of it continues.

 

Try replacing the ECT switch that goes to the ECU. It should be the coolant temp sensor with the plugend.... not one wire.

Hope this helps....

 

I also have been having this same problem for awhile i just turned the idle screw up as a temporary fix but can feel it not idling right still but it inst almost dieing on me as well. driving for 1-2 min would make it go away for me as well. No check engine light

 

Start looking at Distributor and coil components. Air filter dirty? Timing set correctly with Idle? If you have to adavance timing and low idle on the 3.0 you may have these probs as well.