Hello to all, have been searching forum posts for years and have always found my answer, but this one stumps me, Please Help.
Day 1: Changed valve cover gasket. Oil in spark pug tubes. 99.5 A4 Quatro 1.8T 95K mi.

Day 2: Misfiring upon startup idle and had a cel. Like it did when it needed an icm. Misfire and cel immediately go away. My first thought was the icm that I already replaced 2 yrs ago with a HUCO. I decided to see if it comes back.

Day 3 No problems.

Day 4: (ever few minutes) Randomly "bucks" Misfiring? under load with no cel. Pulled codes from day 2 cel at autozone. P0304 cylinder 4 misfire, P0102 MAF low input. (not thesame random multiplemisfire codesI had with the ICM problem)I Deleted codes and went home.First thought is cylinder 4 spark tube not contacting spark plug or coil and causing a misfire which in turn caused the MAF code.
I took the tubeapart and cleaned them again. After 2 test drives no problems! Thought problem solved!

Day 5: Misfires while drivingagain with no cel.I wish it would give me a cel code!PLEASE GIVE THOUGHTS!

 

I get misfires too, no cell. Dealer couldnt fix, but could take my money, big suprise. If you find an answer i would like to know, but i dont think my problems would be that much related to yours, since i never changed the valve cover gasket.

 

sounds similar to my issue too. I only started experiencing these "bucks" under WOT since I got chipped.....Ive never had them at idle though... I am changing my plugs tomorrow and hoping this may solve it.

 

Just back from some more diagnosing, I Pulled the plugs and checked them... all look good since I replaced them at the same time with the icm.
After putting it all back together, I let the car idle. I noticed that the idle has a very slight bounce to it. 5 min. into idling the car choked and almost died just as before. This continued about ever 5 min. I am almost positive it is not a misfire. This is too strong of a choke for a misfire even formultiple cylinders. I started thinking it is the MAF again. But still not one cel code. I decided to check the airfilter again even though i knew it was new and it was fine. As I put the airfilter housing back on I noticed a valve that is above the icm connected to two vacuum hoses. It is totally rotted and broken. I was able to see a rubber gasket\stopper in the broken valve. I started the engine and lifted slightly on this stopper and the car choked again! I thought ah ha. But what is this part? I will go to the dealer tomorrow to find out. I think it is the waste gate. If someone could help I.D. it will be very helpful! My only concern is that the choke that I manually caused only happened that first time. I attempted it again with no choking, just vacuum leaking. I hope this is my cure and not a coincidence. Either way I need to replace broken mystery part.

 

well its only been 2 days since you cleared the code. so im sure it will come back eventually..the ecu just has to pick it up twice in order for the light to come on. if it comes back with a misfire code heres what ide say to do:

take out the coil and plug for the cylinder given in the codeand swap them with different cylinders. dont put them in the same one though. and you might want to mark the coil and plug you are moving too. then, clear the code and wait for the light to come back on. now youve isolated the problem. if its the coil, it will gie u a code for the cylinder you move the coil to. if it the plug it will give u a code for that cylinder. if it gives you the same cylinder, it could be the injector.

 

Just buy bulk vacuum hose from any auto parts store, its real cheap, and just cut it to length.

I think you have found your problem. other things to look at if this does not fix:

Inspect the plug in that cylinder very closely for a hairline crack in the ceramic part
Clean the Throttle body
Do a TB alignment (turn the key on, do not start the car, wait for 60 sec.)
Clean MAF with electrical cleaner or rubbing alchohol

 

Update on Problem...

I have sense replace the check-valve that was rotted out. The result ( which i think is coincidental) was a high MAF input. This causedthe car to run supper rich. I then concluded that the MAF sensor was bad. After shopping around I found the the VW dealer had the best price on the unit at $170. I replace the unit and the car runs GREAT! The misfires thatI was having at first was from a F\A mixture too lean that caused a misfire.

Thanks to all for there help!

 

sick nice pick up man, good 4 you tahts the kind of stuff we need on here ppl figuring weird **** out for them selved and enlightening us all.