Alright here it is, when i come to a complete stop my rpm gauge falls down to its normal spot (800rpm) then about 3~5 seconds later my rpm drops down for a second and my car idles rough, then it immediately jumps back to 800. This issue also occurs when im in idleing in neutral sometimes. And ideas as to what it can be? I also noticed my car idles "rough" (rpms move up and down between 790~820. its hard to notice but its there. Ive already replaced the air filter, spark plugs, dv, bunch of.hoses and bearings, thermostat, fuel filter. There are also no boost/vacuum leaks. Im thinking it the fuel pump because the fuel filter was clogged pretty bad and i dont think it was ever changed. It would also explain my jerky/hesitant acceleration. Ive also already tired injector cleaner too. Your thoughts/feedback on my issue would be great, thanks in advance.

 

Bouncing idle, especially with the other stuff you've covered/replaced already, points me to your primary O2 sensor. Your ECU uses readings from the primary O2 sensor to adjust fuel at idle because there's not enough air going through the MAF to get an accurate reading

 

Ok thanks, ill clean it tomorrow. I dont have any cels and the maf was replaced also. But om thanks ill clean it tomorrow. Any other ideas if that does not work?

 

Cleaning it might not be enough, mine was borked and needed to be replaced.

 

anyway to tell its bad without a cel?

 

Other than the above symptoms and bad gas mileage, not really.

 

yeah i have bad gas mileage. i scanned my car with a special scanner (not your ordinary obdII scanner) and i had a code for bank 1 sensor 2 i thibk it said frequency or volatge was too high. could the secondary sensor also cause these issues?

 

Probably not - that's mainly for catalyst monitoring. The primaries are the fuel mixture controllers.

 

yeah that's what i figured, thanks for the help. By any chance could a bad coils cause this? called up audi and sure enough i have a coil pack recall, i already replaced half the car might aswell get free coils out of it lol.

 

Yes,bad coil packs can cause a rough idle. I bet that's your problem.