QuestionQUESTION: 1990 4Runner (3.0, 5spd, 4wd, 120k miles). After I have been driving the truck long enough to fully warm the motor and then shut the engine off to run in a store, when I return and restart the truck a few minutes later, it idles VERY low (200-300) and obviously, rough. The idle stays low until it has been driven a few more miles and then returns to the appropriate idle rpm. If the engine is shut off for several hours, it will idle fine when restarted. This problems seems to happen more when the air temperature is warm, but this may be my imagination. I am fairly stumped on this one and before I start dumping money into a guessing game, I wanted to ask the expert ;) Thanks for your help.
ANSWER: Is the check engine light ON?
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QUESTION: No the CE light is not on. Tested for codes and didn't find any. FYI - I replaced the throttle position sensor a while ago (5,000 miles) to fix an erratic idle and set it per the FSM (seems adjusted corrected). I don't think this is related, but don't know for sure. I've poked around online and wonder if the cold start injector isn't shutting off like it should on warm restarts. Or, I've read about some kind of wax thermo-valve in the throttle body (can't find too much about it online) that I suppose might cause problems if it isn't shrinking/swelling like it should. Or, I have also thought about the EGR valve - though it has passed a few basic tests, but I haven't ruled it out. Anyways, I've been thinking about it plenty, but really have no clue. Thanks for your help.
ANSWER: If the engine just idles low but not rough then it may help to remove the intake hose from the throttle body and the cleaning the inside of the throttle body with some spray cleaner and a brush, also check for any cracks in the air intake hose or any of the other vacuum hoses.
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QUESTION: I checked for vacuum leaks using an unlit torch and haven't found any. I've run seafoam through the throttle body and visually, it looks clean. The idle is low ONLY after I've driven the truck a while and then shut it off for a brief period of time and restarted. All other times, it idles perfectly, so it seems to me it is related to the motor or a sensor/valve warming up. Any other thoughts?
AnswerIt's possible that the egr valve may be staying open causing the low rough idle, it can be checked with a vacuum pump, by applying vacuum directly to the valve it will reduce the idle and the engine will idle slow and maybe stall, if doing so will duplicate the same condition you are getting while driving then the valve is the problem.
