Implausible signal / misfire on Cylinder 4???

**audballz** · 10-20-2010 11:24 AM

So I've been having my CEL on for about a month now. VAG shows:

2 Faults Found:

16684 - Random/Multiple Cylinder Misfire Detected

P0300 - 008 - Implausible Signal

16688 - Cylinder 4 Misfire Detected

P0304 - 008 - Implausible Signal

I keep clearing but they keep coming back. My coilpacks, spark plugs, and battery have been replaced recently. Also CEL flashes when I'm at a stop light or idling, although idle is not rough. Not all the time but it's happening more frequently. I searched and I couldn't find any threads on just Cylinder 4 misfiring. I replaced all check valves even though original ones didn't look bad. Also cylinder 4 didn't have any traces of oil leaks. What else should I look for?

**Jflow23** · 10-20-2010 11:29 AM

Swap a coil packs between cylinders and see if the misfire moves, I know you said that the coil packs have been replaced but it sounds like a cp issue. Also check your gap on plug 4. You can also swap the plug to see if the misfire moves.

**audballz** · 10-20-2010 11:37 AM

Jflow23,
I did swap coilpacks and it still CEL's on Cyl 4. New NGK plugs gaps are within specs. I forgot to mention that on my first post.

**cdn20valve** · 10-20-2010 12:36 PM

swap injectors.

**audballz** · 10-25-2010 03:49 PM

Swapped Injectors 3 and 4 and still getting misfires on cylinder 4. Cylinder 4 is closest to front bumper right?? So coilpack, spark plug, and injectors have been cleared. Also no signs of oil in Cylinder 4 so gaskets aren't leaking. Anything else to look for?

**cdn20valve** · 10-25-2010 03:54 PM

Two more things it can be.

- Visually check for broken/cracked wires in the coil harness. Also, while the car is running, tug on the harness, and see if the misfires change.
- Next is not good news. Do a compression test. You may find that the suspect cylinder has low compression, and as such not enough to get proper ignition.

Please report back.