P0300 - Removed 3 coil wires no difference
 

2000 S4

Having P0300 so I changed plugs, and ignition control modules.
So I remove one coil wire at a time while running to see if there is any difference. No difference when each of 3 on one side of the engine are removed. Anybody???

vacuum leak somewhere.

I found one little broken vacuum hose and fixed it, but not much of a change.
Can a boost leak cause misfires? saw a pdf on how to make an easy tester.

Found a nice broken non return check valve now. Gonna get that and hopes it fixes.

Replaced broken non return check valve and now I still have P0300 and two new codes.

P0102 Mass or Volume Air Flow Circuit Low Input
P0154 - O2 Sensor Circuit - No ActivIity Detected (Bank 2 Sensor

I had the o2 sensor changed 10,000 miles ago.

you still have a huge intake leak, From MAF to engine boost pipes, air breather, ect. Theres low input from the maf because its just pulling air through the giant air leak not the maf and airbox. The o2 sensor has no activity because the mixture is so lean the o2 sensor is maxed out. both codes are a result of the extreme air leak you have. not failed parts

Yeah going to build one of these next.
http://www.awe-tuning.com/media/pdf/...ure_tester.pdf

Davemark, did you end up fixing the code? I have the same situation! I only have the P0300 code, no individual misfires. Thinking I have a vacuum leak as well.