audiohs

Last weekend, I noticed my car stumbling when I was at WOT between 2000-3500 RPMs. Boost would come on fine to a full 15psi and then drop 1-2 psi each time it stumbled. It would only do it 2 or 3 times and then be fine all the way up the rest of the rev band. No CEL or codes thrown. Originally thought that it was a BPV or leak somehwere.

The next day, I was able to get it to throw a code and got "16684 - Random/Multiple Cylinder Misfire Detected" and "16685 - Cylinder 1 Misfire Detected". So I swapped coilpacks on #1 and #4. I hadn't logged data yet (I'm a VAG-tool n00b) but discovered blocks 15 and 16. Went for a drive and see that it is misfiring in #4. Based on the codes above, I thought it was a coilpack for sure. Go to the dealer and get coilpack and replace #4. Went for drive again but still misfire in #4. So, I swapped both coilpacks and spark plugs between #1 and #4. Go for drive again and now misfiring in #1. I figured that it was the plug so I replace it with Bosch copper plugs.

Now, it is no longer misfiring at WOT as described at the very top but now is registering some misfires at idle. These are very slight misfires and can be barely felt but are there nonetheless. No codes are being thrown either but are registering on blocks 15 and 16 on all cylinders. But it's not happening all the time. I would say that 95%, it idles fine but you can feel it ever so slightly misfire. So tonight I pull the plugs out to check the gap and see that they are .27" (if that). So, I make the gap around .30". Bentley says range is .27 to .35.

The random misfires are basically gone except I am getting the odd one in Cylinder #1 (the one that has the new coilpack too). Still not enough to throw a code.

Looking for ideas as to what it may be. Perhaps my ignition module is on the way out? I had it replaced 2 years ago. I know what it's like when it has failed. Perhaps I need to clean my injectors out? Looking for other ideas.

Thanks.
Henry

Andy_FL

...but someone posted a how-to on checking the power output stage (ICU) with a multi-meter or test light. Was very simple IIRC. Other than that, yeah I'd say it still may not be happy with your plugs--even the new ones. Denso Iridiums caused me all kinds of misfires.....so I trashed 'em and put in "regular" Denso plugs from the local AZ.

If you're still having problems after ruling out everything else, swap in a fresh set of plugs, different brand/type if you can. For $10..... that's cheap compared to any other part that you could replace. nDBW coilpacks seem pretty bulletproof--they're rarely the problem. Good luck

Andy

audiohs

I'm thinking that the test probably would not show up anything since it's so slight. I would need to reproduce the exact currents to maybe get that blip which I don't think a little 1.5V battery could do. The test is good if the igntion amp is really toasted.

So, sounds like I'm on the right path. I'll keep an eye on it. This morning, I didn't hook up the VAG to my car on my way to work and didn't notice anything even if it did misfire...it's that slight. Who knows, maybe my car has been doing this for a while now? I'll try swapping plugs again and rechecking the gap on #1.

Thanks Andy... you always seem to have suggestions helping me with my car problems. Much appreciated.