I have a 1994 Toyota 4Runner 3VZ-E (V6) SR5 with 192K. Recently, it started having problems idling (cold or warm). Symptoms are loping idle from ~200rpm - 1000rpm. Problem comes and goes and does not seem related to the engine temperature. Other than that, the truck runs very well with a smooth acce…

The next time idle lopes, take the handle of a screwdriver and tap on the Idle Air Control valve. If the idle speed changes when doing this replace the IAC valve. Tester

What system does this truck use for “cold starts”? Some use an extra fuel injector in the throttle body and perhaps this injector is not closing properly and dripping in some extra fuel. I would check out the cold start circuits and see if you can locate a problem in it.

RE Tester: I tried tapping the ICV (Idle Control Valve) with a wooden ended screwdriver and there was no change to the loping behavior. I also ran through the diagnostic algorithm in the Toyota shop manual and everything was to spec. RE UncleTurbo: The 3VZ-E uses a cold start injector opposite the …

I’m having the same issue. It does not begin immediately upon start up. It happens after a minute or two during idle. However, mine eventually goes away once the vehicle warms up to operating temperature. I was assuming it’s a sensor, but I have no idea which one? The vehicle runs fine otherwis…

PROBLEM SOLVED! Sorry for the tardy response. Took me a couple of days to get back to this. I ran through the diag algo for the EGR system and found the problem. The EGR vacuum control valve was bad. It was bleeding vacuum at idle causing periodic opening of the EGR valve, which as we all know can …

Glad to hear you nailed it. Thanks for the update. At least it’s not the EGR valve itself, which would have cost way more than $30!

1994 Toyota 4Runner 3VZ-E unstable idle problems

Maintenance/Repairs

db4690 December 9, 2012, 2:04am 5

If you believe it could be the EGR, why don’t you disable it temporarily to see what happens.
It could be stuck partially open, though.

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1994 Toyota 4Runner 3VZ-E unstable idle problems

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