92 Grand Marquis rough idle with a/c

[TavaresE.09]

Hey, just recently i was driving it knowing that everything is up and running "perfectly" and i had the a/c running and while stopped at a red light the engine rough idles and stalled. What could be wrong?

[86VickyLX]

Computer might not be raising the idle when the compressor kicks in. I think that has to do with the IAC. How's your car when it starts cold?

[TavaresE.09]

cold start is fine... no rough idle at all only after its been driven a while on a really hot day... (thermostat reads nothing higher than halfway usually below half of the gauge.) and we turn on the a/c and only stall when stopped at a light or something. Rough idle then stalls

[Grandmarchris]

Are you running a CAI? My old car did that everyonce and awhile

[TavaresE.09]

sorry about all these questions... does CAI stand for Cold Air Intake, and if so then I do not run a cold air intake...

[gadget73]

When was the last time the engine was tuned up? Have you ever cleaned your MAF sensor? Is the vacuum line at the PCV connection cracked? Its a common spot for the line to deteriorate. PCV is on the passenger side valve cover.

[TavaresE.09]

Summer of last year i believe... I don't think we cleaned the MAF sensor... will check all this when I get home later... what would you recommend to use to clean the MAF sensor?

[gadget73]

electrical contact cleaner that says it leaves no residue, or they do sell mass air sensor cleaner for the job.

[91waggin]

This happened to me recently, and it turned out that the A/C compressor was almost shot, and was putting so much drag on the belt that it was pulling the belt to a stop and stalling the engine out. Take the car to an A/C shop and have the system checked. Make sure there is the right ratio of oil to refrigerant in the system. If you have a way of verifying that this is the problem, DON'T RUN THE A/C. You could do even more damage to the compressor (like I did) and have to replace the compressor and most of the system because the compressor completely froze up and shat metal shavings into the rest of the system.

[TavaresE.09]

91 waggin sounds like the problem... I've been playing around with that... turning the a/c on and off comparing the idle... and it seems to have a tendency to run rough and idle rough when the a/c is on... thanks will check it out this weekend

[Chevyguy]

the IAC "intake Air Charge valve" famous for getting clogged up and the motor gets tired.

Cleaning is useless, replace with a new unit and clean the orifice in the intake.

Not bad advice to check out The AC before using it further and causing massive damage. R-12 is EXPENSIVE

[91waggin]

the IAC "intake Air Charge valve" famous for getting clogged up and the motor gets tired.

Cleaning is useless, replace with a new unit and clean the orifice in the intake.

Not bad advice to check out The AC before using it further and causing massive damage. R-12 is EXPENSIVE

R-12 isn't that bad, and a R-134 upgrade isn't that bad either. BUT the compressor, receiver/drier, orifice tube, and the lines are hella expensive, plus labor if you don't do it yourself (I didn't because I don't have the know-how or equipment when it comes to a/c).

Also, IAC stands for Idle Air Control. And cleaning it does help.