Looking for help sort of tricky(P0303)
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LET C32 2002
Looking for help sort of tricky(P0303)
I have a P0303 that ONLY shows up at first start of day ONLY IF I let car idle to warm up usually after secondary air pump turns off. Now IF I just turn car on and go...no warning ever shows up and car runs perfect. I can't work on it until weekends when my buddy has time to help me. I've done new plugs,swapped coil packs several times as well as spark plug wires and even fuel filter since it has the regulator. Code only shows up at cylinder 3...I haven't done compression test cause since car pulls hard even at WOT it tells me it can't be compression based...I doubt it has to do with cats cause like I said car pulls hard no problems no hiccups..If it were to be fuel I'd expect multiple cylinder misfires everytime instead of one. My next step is swapping injectors to see if code follows that cylinder. If anyone has feedback or schematics of DIY I'd appreciate it.
Thread Starter
MBWorld Fanatic!
Joined: Feb 2006
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LET C32 2002
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MBWorld Fanatic!
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From: Washington DC
1999 E320 4matic Wagon, 2005 C55 AMG - sold, 1998 VW Jetta TDI - sold, 2006 C230 Sport - Totaled :(
So you tried swapping coil packs and wires already...did you try swapping plugs to see if the code moves then? Then you can see if maybe it's a bad plug. Have you had the plugs changed recently?
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Thread Starter
MBWorld Fanatic!
Joined: Feb 2006
Posts: 6,213
Likes: 8
LET C32 2002
Thread Starter
MBWorld Fanatic!
Joined: Feb 2006
Posts: 6,213
Likes: 8
LET C32 2002
Here's info again:
I've had a fault p0303 that's a misfire cylinder 3. It only shows up when car is cold basically fresh start of day I don't think outside temp matters cause in summer with 70+ it still happened. I was monitoring today with full air boxes and splitter off leaving throttle body fully exposed and one hose open at valve cover on drivers side and noticed as usual engine light comes on after secondary air pump turns off...car engine temperature was under 40 degrees at that time. I reset code and turned car off then on temperature was around 50-55 eventually warning code p0303 showed again. I waited til car engine temp at 60+ and reset code then turned car off then on again and NO codes. Now IF I just turn car on and drive NO codes appear at all. I've already:
1. installed new plugs rechecked again by me and a shop swapped also
2. Swapped coil pack many time last was from cylinder 6 to 3 and still code in same cylinder 3 (p0303)
3. Changed fuel filter since regulator in it.
4. Checked and still monitor fuel rail pressure when on constant 60 p.s.i.
5. Swapped spark plug wires several times even tried factory wires.
I'm told could be a vacuum leak but today I had full air boxes off including splitter...thus hose from splitter going to second opening from valve cover was exposed but no code at all when engine warm 60+
I was told compression but like I said IF I turn car on and drive before secondary air pump finishes NO codes at all and car runs perfect.
I was told injector but this car by what I'm told doesn't have a history of bad injectors and when car engine warm car runs perfect but I still feel at cold start maybe injector cylinder 3 could be intermittently faulty
I was told Cats but how does car run perfect even at WOT with even a cat going bad
I've had a fault p0303 that's a misfire cylinder 3. It only shows up when car is cold basically fresh start of day I don't think outside temp matters cause in summer with 70+ it still happened. I was monitoring today with full air boxes and splitter off leaving throttle body fully exposed and one hose open at valve cover on drivers side and noticed as usual engine light comes on after secondary air pump turns off...car engine temperature was under 40 degrees at that time. I reset code and turned car off then on temperature was around 50-55 eventually warning code p0303 showed again. I waited til car engine temp at 60+ and reset code then turned car off then on again and NO codes. Now IF I just turn car on and drive NO codes appear at all. I've already:
1. installed new plugs rechecked again by me and a shop swapped also
2. Swapped coil pack many time last was from cylinder 6 to 3 and still code in same cylinder 3 (p0303)
3. Changed fuel filter since regulator in it.
4. Checked and still monitor fuel rail pressure when on constant 60 p.s.i.
5. Swapped spark plug wires several times even tried factory wires.
I'm told could be a vacuum leak but today I had full air boxes off including splitter...thus hose from splitter going to second opening from valve cover was exposed but no code at all when engine warm 60+
I was told compression but like I said IF I turn car on and drive before secondary air pump finishes NO codes at all and car runs perfect.
I was told injector but this car by what I'm told doesn't have a history of bad injectors and when car engine warm car runs perfect but I still feel at cold start maybe injector cylinder 3 could be intermittently faulty
I was told Cats but how does car run perfect even at WOT with even a cat going bad
Last edited by c32used; Feb 6, 2015 at 03:41 PM.
