RPM Jump

01yellercobra · Feb 19, 2020

On my son's 99 GT when he turns on the A/C or defroster the RPM will jump up to about 1500rpm. It does it with or without a tune in it. My initial thought is the IAC. But I've never had them cause a jump in RPM. Usually they go the other way in my experience. What do you guys think?

evilcw311 · Feb 20, 2020

Bad iac can cause an rpm jump.

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white95 · Feb 20, 2020

Where does it idle prior to turning the AC on? The AC kick should bring the RPM's to around 1000.

How many miles? It's possible the clutch/compressor is working harder than normal due to age related wear [clogged orifice, low/high line pressure, etc]

01yellercobra · Feb 20, 2020

Without the tune it idles whatever the stock rpm is. With the tune it idles at 750 since that's where I have it set.

I want to say it has 167k or 168k on it.

OLD H2S · Feb 23, 2020

Or the TPS is jumping from 1 volt idle read to 9 volt spark read at the PCM.
Loosen the TPS screws just a little bit and wiggle the hosing back and forth 1mm, twist counterclockwise wise gently and tighten down the screws and see what changes..

01yellercobra · Mar 24, 2020

Swapped out the IAC and all is well. He finally got around to it.

evilcw311 · Mar 25, 2020

Huh........I don’t wanna say I told ya.............

......but I will!!!!! I told ya, I told ya!!!!! [emoji1787]

I know, I’m childish at times....... [emoji23]

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ttocs · Mar 25, 2020

evilcw311 said:
Huh........I don’t wanna say I told ya.............

......but I will!!!!! I told ya, I told ya!!!!! [emoji1787]

I know, I’m childish at times....... [emoji23]

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good call on the IAC, but it took you nearly 35 mins to answer it. If you do not start to do better we might need to discuss a punishment.

evilcw311 · Mar 25, 2020

ttocs said:
good call on the IAC, but it took you nearly 35 mins to answer it. If you do not start to do better we might need to discuss a punishment.

Between your grumpiness, white bustin my balls, and blak’s crazy hairbrained schemes.....

......not sure I could be punished more!!! [emoji38]

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