Car shakes then stops when at a light it is worse when AC is on what could it be?

Answer 1

Possible cause poor fuel pressure. Replace fuel filter first. Doesn't solve problem check fuel presure. Need to know what kind of car you have for futher diagnostics. You're fuel pump may be bad. There are other things that can cause this but need more information.

Your car may be equipped with an Air Conditioning Idle Valve which increases idle speed when the air conditioning compressor engages to compensate for the greater power required to run it. If the A/C Idle Valve is not functioning properly and switching on, then the A/C compressor needs more rpms than your motor is producing at standard idle, and pulling power from the engine itself.

my car does the same 93 maxima se manual transmission. I checked and found out that two of the cylinders are not working so the car is running on 4 cylinders. And that's why the car shakes when the a/c is on not enough power. I plan to either wait till the car gives up or buy a rebuilt engine.

Clean the IAC valve. I had the same problem and I did tune up, changed fuel filter but it still remained same. Then I opened the IAC valve from the throttle body and cleaned it's dust using a Carb cleaner (walmart) and from the very next ride, the AC went normal.. even when idle.

- Sam

It could be your idle control motor (or servo kit), it's part of the fuel induction system and basically regulates air intake. (A new idle control motor should run you about about $200). I had to replace this on my Mitsubishi it cost me $183 to do it myself, which is alot better than what the mechanic wanted ($670.00!!!!)