Maxima Forums - Daniel Martin,I did the test with the AC my RPM's went up when i turned the AC on

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- - Daniel Martin,I did the test with the AC my RPM's went up when i turned the AC on (https://maxima.org/forums/4th-generation-maxima-1995-1999/47132-daniel-martin-i-did-test-ac-my-rpms-went-up-when-i-turned-ac.html)

I did the test that you told me to do. I turned my car on ran it to normal operating temperature and then turned the AC from off to High my RPM's went from about 500 to 700 and then back down to 500. Why did they do this? Emax says it may be my Mass air flow sensor do you think that could be it? You said my RPM's should dip and then recover I wasnt expecting them to go up and then back down. I did the test more than once and it did the same thing every time. I dont have the equipment to do the other test you told me to try. Thanks again for your help it is greatly appreciated! Thanks

Quote:

Originally posted by pimpman81
I did the test that you told me to do. I turned my car on ran it to normal operating temperature and then turned the AC from off to High my RPM's went from about 500 to 700 and then back down to 500. Why did they do this? Emax says it may be my Mass air flow sensor do you think that could be it? You said my RPM's should dip and then recover I wasnt expecting them to go up and then back down. I did the test more than once and it did the same thing every time. I dont have the equipment to do the other test you told me to try. Thanks again for your help it is greatly appreciated! Thanks

The results you report suggest (but do not guarantee) that your IACV-AAC valve is good. Now you have to look further...
- vacuum leak (damaged or disconnected vacuum line)
- crack in the black plastic air duct which conveys filtered air to the Throttle Body
- dirty Throttle Body interior
- bad Positive Crankcase Ventilation valve
- stuck-open Exhaust Gas Recirculation valve

Wouldnt the RPM vary when the AC compressor turns on?

Quote:

Originally posted by mzmtg
Wouldnt the RPM vary when the AC compressor turns on?

Yes. The added load on the engine causes the idle speed to drop below normal and the IACV-AAC valve is supposed to compensate by admitting a little bit of air. This is equivalent to the driver stepping on the accelerator just a bit.

We are accustomed to calling the accelerator "the gas pedal". With our modern fuel-injected engines it might be more correct to call it "the air pedal".