# Misfires and CEL after Timing Belt Change



## jollespm (Aug 18, 2000)

My 2002 2.8 V6 car was running fine for a couple weeks after I bought it used with 58000 miles. The first thing that started to go wrong was the spark plug wells started to fill with oil. I've read that was common, so I ordered valve cover gaskets, checked the PCV stuff, and parts to do the timing belt job while I was in there. I've completed all that with new cam seals, spark plugs, plug wires, etc.. When I first got the car back together, it started one time, made some awful clattering, and wouldn't start again.
Fearing the worst, I had the car towed to my local mechanic, where they were able to tweak the timing and get the car running again, but it was low in compression on the drivers side, and misfired like crazy. They suspected bent valves.
I got the car home and proceeded to remove the drivers side head, and had it inspected. There were no bent valves, but the head was warped about 7 thousandths. To be safe, it was decked, and I had the shop install the cams and timing chain in the head so I wouldn't be tempted to screw that up.
I put the head back on the car and it started up easily, idled well, but any time I got on the throttle it starts misfiring and throwing codes again. Watching with VAG-COM, I have to get up to ~2000-2500 RPM for the misfires to really get bad. If I go get up to 3000-3500 the misfires seem to go away, or at least frop from the 45-60 range back to 4-5. Is there some variable valve adjustment kicking in at some point? Higher oil pressure on the cam chain tensioner?
The codes I'm getting are:
16730 - Camshaft Position Sensor (G163): Implausible Signal
P0346 - 35-10 - - - Intermittent
16684 - Random/Multiple Cylinder Misfire Detected
P0300 - 35-00 - -
16688 - Cylinder 4 Misfire Detected
P0304 - 35-00 - -
16689 - Cylinder 5 Misfire Detected
P0305 - 35-00 - -
I also get misfires on 6, I just didn't let the car run long enough to trip the code. Using VAG-COM I've checked the cam tensioner (block 094) and that test comes back ok. I've ruled out a bad cam position sensor, I've swapped them side to side, along with trying a known good one. I've double and triple checked the timing with TDC and the cam locking bar.
I've got the car apart again and took a few photos of the cam position to make sure they were ok.
Exhaust Cam








Intake Cam








The intake cam doesn't look like it's lined up well, but if I rotated it one tooth, it doesn't appear that it would be any better. I currently have 16 pins between the engaged teeth on the sprockets, so I'm pretty sure everything is ok.
On top of all this, I did a compression test and cylinder 1-2-3 are at 145+, while cylinders 4-5-6 are all about 115. I'm not sure if this is related to the misfires and cam position, or just another issue I didn't know I had before I started. As I mentioned before, I just pulled the head off and there were no bent valves, and the head isn't warped. I'm guessing it must be rings, but it seems odd to only happen on one side. I had someone mention they had a similar misfire/compression issue and it was lifters, but I've got the cam position errors thrown in as well.
I'm at a loss of what to do next. I suppose the cam tensioner could be mechanically bad, and is allowing the cams to be out of sync, is that even possible? Any other ideas? I've owned this car for almost 2 months and have had it torn apart for 6 weeks!


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## Slimjimmn (Apr 8, 2006)

*Re: Misfires and CEL after Timing Belt Change (jollespm)*

#1- did you use new head bolts
#2- That lower cam is off 1 tooth for sure. It should be somewhat on the arrow. (its usually like 1/2 in the arrow) but that ones totally off 1 tooth. 
You will need to pull the cams on that head and re-adjust them. Note you need the black plastic special tool (i think 3366?) to pull the adjuster together to releive tension on the adjuster so you can properly time the cams. http://cgi.ebay.com/ebaymotors...Tools


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## jollespm (Aug 18, 2000)

*Re: Misfires and CEL after Timing Belt Change (Slimjimmn)*

Yes, I did use new head bolts when I put the head back on.
As it turns out, after looking at it again, I came to the same conclusion you did, that the intake cam had to be off by one tooth. So I tore it all apart, again, and reset it. 3 hours later, the car starts up, no error codes. All my problems the whole time was that I marked the cam wrong and put it back together incorrectly.
What a headache, but I'm glad it's been figured out. I appreciate the help. Now I just hope I don't have any leaking fluids. I don't want to take this apart for another 60000 miles.


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