My car has doing the acting weird for a few months now, but I have no clue what it could be. When I'm at idle (red light), the car shakes real quick like the voltage drops or something. Only for a split second and then returns to normal. Like if someone was playing with the coils or something. Anyone know what this is or how to fix?

 

Rpm's drops too

 

A/C on or off? How old is the battery? Hows the alternator?

 

Battery has nothing to do with running of engine after battery powers up starter. Car runs entirely on alternator. (All cars work like this.)

1. moisture in fuel system. Try drygas or a top tier brand of gasoline. It may take several tanks. Do not use cheap gasoline. Period.

2. Fuel filter??

3. Attach wooden close pin to fuel line under hood if you can get to it. It will assist in eliminating vapor lock in fuel line.

4. Other??

 

I would change the spark plugs first.

 

It could be an ignition coil on one of the cylinders is going bad.

 

Thanks for all the advice. I only use shell v power but I'm at 80k and have to do a service. Maybe it's that. What should I do?

 

I think you answered your own question. I don't know if it would do any good, but I would run by an Auto Zone store and have them use the OBD II to see if any codes pop up. Can't hurt. In the mean time start with the simple things/least costly things first.

Interested in finding out what happens.

 

See if you can get someone to check the code, my 550 did the same thing, it turned out to be the coil, I ordered one at the store, oddly enough it's nit that expensive for a BMW part, lol. Changing it took all of 15-20 min.

 

+ 1 .... at 80K might be time. Lumpy idle .... I'd do a quick investigation first to be sure it's not something simple like a vacuum leak or a loose oil filler cap.