Car ran very well and then the Starter went and the car sat for a few weeks.

I replaced the starter and the ignition switch and the car started right up but ran rough very rough and the throttle was out of whack. Did a throttle body alignment on the vag and after that throttle was fine but car still ran just a little rough at idle so I cleaned the throttle body

At this point, the car still ran rough at idle. The check engine light was on and 7 codes came up so I replaced the vacuum tubes to try to solve some of the rough idle problems. It did not solve the rough idle problems but it took care of some of the codes.

Car still idles somewhat rough and my vag-com gave me the following cylinder misfire codes.

P0300 - Random/Multiple Misfire Detected
P0301 - Cylinder 1 Misfire Detected
P0302 - Cylinder 2 Misfire Detected
P0303 - Cylinder 3 Misfire Detected
P0306 - Cylinder 6 Misfire Detected - Intermittant

I am getting ready to diagnose these problems and my first step is probably either a compression test or spark plug replacement. I have only owned the car for a few months and to my knowledge, they haven't been replaced. I am selling the car so I am just looking for basic solutions. Any idea of the steps I should take?

Also, I have a 98 A4 2.8 and I can't find the idle control valve. I followed a diy for cleaning it but the location of the picture they take of the icv, is not on my car. I looked there...right next to the throttle body and did not see the cylindrical black piece as shown in the diy...does anyone know where it is?

 

I'd first replace all the plugs with some NGK's and make sure they are gapped perfectly. I learned that too small a gap creates rough idle and too large a gap can cause misfires. If that doesn't solve the problem, new ignition coils should be the next thing to consider.

 

There's no reason to think you've lost engine compression as a result of sitting a few weeks. Also the 2.8 coils aren't known for failure like those in the 1.8T. How much gas is in the car?

 

There Is just under half a tank in the car.

 

That's more than enough empty volume to get a lot of moisture in the tank. You may just have gas that's watered down from sitting.

 

Filled the tank and installed new plugs gapped to about .037. Still idling rough. Any other suggestions? The idle seems low...can someone tell me where the idle control valve is?

 

VAG-COM gave me a misfire on all the same cylinders. What do I do next?

 

Bring the gap down to .032" (that is what's called for by Audi). See if that helps at all.

 

is it possible to lower the gap? how do you do it?

 

changed the gap on the new plugs and the idle is still rough.

BTW the part # forthe spark plugs i used is BKR6EGP and the NGK.