I really need a Volkswagen expert for this one.

Question

I had a 99 Passat 1.8 turbo (engine AEB) come to me running rough, with the check engine light on. Had codes P0300 and P0302 (16684, 16686). Found the spark plug tubes full of oil, and some leaky injector o-rings. Replaced the valve cover gasket set, spark plugs, ignition coil boots, all eight injector o-rings, and ultimately, injector #2. Still runs like it did when it came in. Compression is perfect, I don't remember the specific reading, but no more than 2 psi difference at most, and fuel pump is generating 80 psi at the fuel rail. Anyone know what else might be causing this?

Answer 1

P0300 is multiple cylinder missfire, isn't it? and P0302 is cylinder #2 missfire, I believe. If you changed all that already and still running rough, Its most likely the #2 coil pack. Try to switch the #2 spark plug coil pack with any other coil and erase the check engine light the code should change to that number cylinder. If you by ignition coil boot you are referring to the coil pack.  Then it will be the secondary ignition switch, or igniter located on the air filter box. Hope this helps out, good luck!  

Answer 2

I agree that the ignitor unit on the air filter box is a good bet. Has been for me on last two 1.8T's  that  I've seen with the same symptoms.