[ds968]

When I started the car today the RPM immediately shot up to about 2K and remained stuck at that level . It was not " hunting " up and down or surging further, just consistently stayed in the same spot. I waited for a good minute or more to see if it restores itself but no luck. With the engine still running, I opened the hood to see if the throttle cable was caught up somewhere but all seemed normal there . I pulled and then released the lever which came back to its full resting position very easily but the idle rpm still did not change . So I turned off the car, waited about five seconds and started it again to see if anything changes, while for inexplicable reasons feeling almost certain that when it does restart it'll be just fine . And of course it did ! Car restarted perfectly fine, the RPM idled exactly where and how it's supposed to do , I drove it off to run some errands, many restarts during that time and no problems .

Electrical gremlin ? Mechanical gremlin ?

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[Rap]

Which car

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[ds968]

Green one ( tiptronic ) . But why would it make any difference , they have an identical set up ...and certainly this is not a transmission issue ?! I thought maybe the ICV got briefly stuck for whatever reason .

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[Rap]

ECU ?

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[ds968]

I guess nothing is impossible, but seems unlikely something which is programmed would cause an isolated , one time glitch , and then just revert back to normal .

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[banditsc]

I would bet on the ICV getting hung up, they can get sticky with age, some have had luck cleaning them, or shooting WD-40 into the hose, but that is usually just short lived relief. The only way the ECU can increase the idle is with the ICV, it's not drive by wire so it can't move the throttle plate, only introduce more air by opening up the ICV.

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[ds968]

noted, thanks.  yesterday morning it started and idled normally also.     

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[MCL968]

I would clean the ICV connector too. May have just been a flaky connection.

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[banditsc]

If it happens again, pinch off the ICV hose and see what happens to the idle.

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[ds968]

The ICV connector is new ( well, recently new - less than several months ago , worked perfectly fine so far..)

 

Hmm, if it happens again I'll try that .. are you thinking maybe a very small vacuum leak which needed just the right conditions to manifest itself and then in absence of such, acts normally again    ? 

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[banditsc]

No, if it's stuck open it's feeding a bunch of air into the engine, thus raising the idle, if you pinch off that hose that is feeding the extra air in it should drop the idle down.

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[ds968]

Ah, got it .

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[az968]

Did you Check where your floor mat was, maybe jammed up against the pedal?

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[flash]

have you yet corrected the throttle plate position, and calibrated the TPS?

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[ds968]

1) Yes, at the same time all that work was done on the ICV, sensors, throttle, etc. the and 2) waiting for the mechanic to return from vacation so he can check and re-calibrate the TPS, in case the first calibration ( during the above mentioned job ) was off .

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[flash]

if the TPS calibration is off, the ECU will not really know where things are, and the ICV could be fooled into opening when it shouldn't, resulting in a high idle

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[ds968]

May be the case , but keep in mind this happened only ONCE , never before and never after .. the gas pedal's long travel before adequate response I understand can be easily tied to the TPS calibration, but that's consistent .. This high revving incident is just once out of countless starts ..

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[flash]

not if you consider the other items involved.  they all work together to tell the ECU what to do.  where the engine is told to idle is determined by readings from temp sensors, the MAF, the ICV, and the TPS.  they all have to be happy together for things to work right.

 

get that thing calibrated.

 

did you ever replace the ICV, or just assume that the connector was the issue there?

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[ds968]

ICV was not replaced - no need , because it was was removed, tested thoroughly ( manually ) and determined to be in very good order, and clean , even before additional cleaning was done to it for safe measure , so no doubt it was the connector . The starting idle has been perfectly fine ever since . Until that one day ..and then back to normal , as of nothing ever happened. But yeah, checking calibration of the TPS soon .

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