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View Full Version : Unknown misfire source, Please Help!



UbErKoOl B5
06-27-2013, 11:17 AM
Hello all,

Im a newbie here but am also member of Audiforums, due to recent suggestions have decided to join Audizine and was hoping you guys could offer a bit of advice. Also would like to offer my apologies in advance if this topic has already been discussed. I presently own a 97' audi a4 2.8 quattro sohc afc which is my pride and joy aside from this insane misfire which I cannot seem to locate the source of. I recently had the timing belt/water pump kit installed by a local indy shop for around $750, 2 days later on the way to work I noticed a slight stall as i attempted to accelerate off of a busy exit and merge into traffic. I didn't think much of it til the symptoms returned later that day finally causing the check engine light to illuminate. By this time I already had an ignition coil on it's way to RAI motor sports in preparation for a trip as I have encountered these issues previously. The codes were 0300, 304, and 306 i believe, can't recall because I cleared them w/my OBII awaiting the arrival of my coil with confidence. I installed the new prenco unit they had overnighted the next day and the car ran great even at idle for approx 30mins. Since then I have had a new prenco coil installed along w/brand new ngk wires and spark plugs. The codes are now 0300, 302, and 304 with cyl. 2 confirmed with my starter version of ross tech vag com. I am aware I need valve cover gaskets and will be tackling tomorrow more than likely, but on this particular model they do not cause much oil to seep to the sparks since they are not centered like in the dohc models 98'+ right? Also thinking possibly injectors? Any help would be greatly appreciated, will need this vehicle running ASAP

UbErKoOl B5
06-27-2013, 11:18 AM
Have also been told that the timing may be off by a tooth and have heard that it may need an ecu flash to compensate for the "tightness" of the new belt. My local Audi dealership stated that a flash would need to be performed, but Im not sure if the young girl I was speaking with was simply attempting to generate business. At this point the $130 diagnostic fee doesnt seem too bad to pinpoint the issue so that I may begin repairs.

UbErKoOl B5
06-27-2013, 11:21 AM
Additional info to present day

Icm swapped from 94' audi 100 I believe, courtesy of a local junk yard, same part id#, no dice! Still misfiring like crazy codes 0300, 302, 304, 305 now also, even tried swapping back to original icm, same results.

Parts replaced;
ignition wires
spark plugs
ignition coil (2x under warranty)
icm

Will try some injector cleaner later, made an appt with my local indy who did my timing belt for monday, trying to avoid it though, any additional suggestions folks? Am also planning to do my valve cover gaskets tonight but I do not believe they are the culprit.

UbErKoOl B5
06-28-2013, 05:30 AM
All fuses checked and in tact, any additional suggestions prior to Monday would be greatly appreciated

Kamil`
06-28-2013, 09:19 AM
Did the mechanic lock your camshafts in place while doing the timing procedure? If not he messed up your timing, even by a fraction, and that is why you are getting misfires. Timing is crucial to any motor. Bad timing results in destroyed valves, destroyed combustion chamber, destroyed piston. It can even warp your rods from the pounding, even if the pounding is so small you can barely feel it. If you don't fix it soon you might as well buy yourself a short block or a used motor.

I am no expert but I really think your timing is off. Once the timing is correct, you should have no issues. Leaky gaskets are bad but I have had leaks on my 30v 2.8 and never experienced misfire issues.

Fingers crossed. I probably just jinxed myself.

Kamil`
06-28-2013, 09:26 AM
I also did the whole timing procedure a couple months ago and didn't flash my ECU or whatever. Like I said, it is crucial to have the camshaft locking tool so your timing doesn't shift.
If you ask your mechanic if he did everything properly he will probably say yes, they never admit to their mistakes. I could be wrong myself, and maybe your timing is okay and you have other issues.

Those codes you are getting, post their exact description over here. It is possible that your speed sensor and/or knock sensor are shot also. If they aren't working properly the ECU isn't getting the correct information
regarding the position of the piston in the cylinder. If the ECU doesn't know where the piston is, it could be opening the valves a little too late or the valve overlap (known as VTEC on ricer Hondas), also known as variable valve timing, is causing the valves to hit the piston when it reaches TDC.

UbErKoOl B5
06-28-2013, 12:06 PM
Just cleaned my maf and unpluged it due to advice frm another forum, no behavioral change in either case, will pull most recent codes and post shortly. My mechanic stated that he used the locking tool when changing the timing belt and also showed me pictures, but that does not mean that it is not off by a tooth as the proceedure was not documented step by step.

Not too sure about the speed/knock sensor(s) but i doubt it due to the fact that the vehicle behaved flawlessly in that aspect for over a year, I would park it for approx 3-4mo at a time then drive it spontaneously while either my dd was being serviced or for leisure and I had virtually no issues til two days following this timing belt job.

amansoor
07-02-2013, 10:18 PM
check the pcv valve as well