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Old 08-19-2011, 12:03 AM
1st Gear
Join Date: Aug 2011
Posts: 5
Angry [resolved] Loosing my mind: Misfire on 2003 A4 1.8T

Driving for about 10 minutes, pull over and put it in park and the idle jumps to 1500. Nothing was wrong before, so i drove home which was about a 5 min ride. Turned it off and back on and it started shaking at idle. The RPM's slowly rose to 1500 so i got out to look at the engine and noticed a hissing noise. I listened and it sounded like it was coming from a check valve so i wiggled it and it snapped right off. So i replaced that and it didn't help.

Still idling rough so i go to auto zone and get replacement coil packs. No dice. After the car runs for a while the RPMs go high again so i opened the hood and checked the MAF connector. Unplugged it and the RPMs go back to normal, plug it back in and nothing changes, still normal, still misfiring.

Go buy a basic OBDII scanner and read codes: P0300 P0301 P0302 P0303 P0304 P0171 P0507. Got new spark plugs, engine air filter and MAF cleaner. Cleaned the MAF and installed the plugs, no change but RPMs are normal and misfire still exists.

Went to Audi and got new NGK plugs, a new MAF sensor, New dipstick (The seal on mine was bad). Cleaned the throttle body with throttle body cleaner and cleaned connectors on coil packs and MAF sensor. Cleared all codes and disconnected the battery for a bit. SAME DAM THING!!! Still idling super rough and throwing all misfire codes. I hear a hiss still on the right side of the engine but i searched for hours for a leak. I did the smoke test and zone isolation with a towel. If i drive the car it seems to lose a little oil from the dipstick area but the oil level reads fine.

Ive tried swapping coil packs and plugs. I've traced the MAF sensor wires and checked for and verified power to that sensor with a test light.

Symptoms: Misfiring, shaking
OBDII Codes: P0300 P0301 P0302 P0303 P0304 P0171 P0507
Replaced: Coil Packs (non-OEM), OEM MAF, OEM Plugs, Non-return check valve, Spark Plugs, Engine Filter.


The things i've seen on this forum but don't know which i should try are:

ICM, Diverter Valve, Fuel Filter.

Last edited by supersix4our; 08-22-2011 at 09:42 PM. Reason: solved
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Old 08-19-2011, 01:01 AM
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Join Date: Apr 2007
Posts: 6

check for vaccum leak and check fuel pressure. or maybe there is this round diverter valve on top of the engine, inside the dv the rubber seal usually goes bad. if thats bad u have to change that part. It seems more like vaccum leak problem, pretty sure its that.

Last edited by a4ak4boost; 08-19-2011 at 01:07 AM.
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Old 08-19-2011, 10:22 PM
1st Gear
Join Date: Aug 2011
Posts: 5

So i narrowed the issue down to one hose today by taking a tube and listening around in the engine. I realized the hissing noise was coming from an entire area and decided to squeeze the hose and wala! My engine went back to normal idle, the hissing sound went away and the misfires stopped immediately.

Now obviously i cannot keep the wire pinched so I still have a problem.

Click the image to open in full size.

The hose leads into the part labeled 06a-103-247 (that is not my picture) which i believe is a breather valve or pcv valve.
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Old 08-20-2011, 09:14 PM
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Join Date: Aug 2011
Posts: 5

Pulled the pvc valve out and the spring inside was stuck. Hopefully thats what it is.
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Old 08-22-2011, 09:41 PM
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Join Date: Aug 2011
Posts: 5

For those that bump into this thread it was the PCV valve. However Audi does not call it a PCV they referred to it as a bleeder valve although it appears to server the same purpose. The part number for it is 06B-103-245.

Car is running like a champ now.
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Old 12-11-2011, 06:45 AM
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Join Date: Dec 2009
Posts: 21

Originally Posted by supersix4our View Post
So i narrowed the issue down to one hose today by taking a tube and listening around in the engine.
Click the image to open in full size.
Nice picture!!! I just had to replace all of that... Question, how did you find the spring in the pressure valve? Did you actually pull it apart or was it a simple view after removing it from the system???
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