Idle issues

[Brandon++S]

97 z28 m6 tuned by pcm for less. Idles high until completely stopped for about 2 seconds then comes down to where it should be. Sorry if this has been covered before but is this tuning or vacuum etc?

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[Camaro96]

We have a sponsor of the form MoeHorsePower. I'm not sure why people are use PCM for less. Almost everyone that I see that has a tune from them have issues or is unhappy.

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[Brandon++S]

Yes unfortunately wasn't active on this forum at the time of my build and really didn't know who to use

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[MoeHorsePower]

Its probably in the tune, but what you can try is to close the throttle blades just a hair and see what happens, if it starts surging then the tune will have to be adjusted.

[Brandon++S]

Thank you, I will have to try that this weekend

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[Brandon++S]

MoeHorsePower it was tuned for 52mm tb and I'm still running stock would that cause this type of issue?

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[Injuneer]

Check your closed throttle TPS voltage. Check the reading on the coolant temp sensor (the one in the water pump housing) - PCM elevates idle speed when engine is cold. Check the IAC "counts" to see how the PCM is reacting to the high idle. If the counts are bottomed out at "0" you may have a problem with the IAC valve. Is the SES light on? Have you scanned it for codes?

Might want to list all the major engine mods.

[Brandon++S]

Le heads cam, 227/235, long tubes, ory. No emissions. Only code I've had is o2 heater..it only idles high while rolling,when stopped at red light takes about 2 seconds for it to come down and idles fine. It's 109 lsa so pretty choppy idle nothing extreme. No issues on cold start at all

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[Injuneer]

Hopefully Moe can comment, but I believe as long as the car is moving (VSS not = O), the PCM opens up IAC to prevent the engine from stalling if the throttle blades suddenly close. It's normal for the idle to stay a bit higher until the car comes to a stop.

[SSlowBoat]

Hopefully Moe can comment, but I believe as long as the car is moving (VSS not = O), the PCM opens up IAC to prevent the engine from stalling if the throttle blades suddenly close. It's normal for the idle to stay a bit higher until the car comes to a stop.
I had a bad vss connection and it would randomly read 1-2 mph so it would idle high in my first 94 z28. I believe you are correct

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[Brandon++S]

Thanks Injuneer that makes more sense I was thinking maybe it was keeping idle up for vacuum purposes for brakes etc. That may be a little old school thinking....lol

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[MoeHorsePower]

Pretty much what injuneer stated, check everything he noted, if it's idling for more than 3 seconds, it can be lowered a bit.

[Brandon++S]

Thanks for all the replies

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