The Stig

Hey all,

Last week my MIL light came on and flashed a few times, the codes came up as misfires in cylinders 1, 3 and 5. After resetting the codes the MIL light came back on, flashed a few times indicating more misfires.

The battery died while scanning so I changed it that night.

The next day, the MIL light stayed on without a single flash, however the next day it flashed every time the RPM's hit 2200 in 2nd-4th gear (automatic transmission).

Yesterday it wouldn't start. I towed it to a mechanic (regular audi mechanic couldn't get me in for 3 weeks so I took it to a guy who does basic work out of his garage who I trust) and the codes again showed misfires in 1, 3 and 5 and a crankshaft position sensor code also came up. I had already bought spark plugs, wires and an ignition coil so we changed that out hoping for the best, but no luck, it still won't start. It sounds like it's trying to, but ultimately fails.

Would replacing the crankshaft position sensor fix this issue or is it something more serious?

The Stig

Update: I have now replaced the crankshaft position sensor and the only change is that a new code is coming up for the camshaft position sensor bank 1. The car still won't start.

Any advice would be appreciated, even as simple as where this sensor is located on the 2.8L engine so I can test the voltage to it.

The Stig

Update: The camshaft sensor has been replaced and was cracked - clearly what was causing the engine to not start.

The car will now start and runs fine, but I am still getting the codes p0300 - random cylinder misfire, p0301 - cylinder 1 misfire, p0302 - cylinder 2 misfire, p0303 - cylinder 3 misfire, p1338 - camshaft position sensor bank 1 short to ground, essentially putting me right back where I started before I changed out the plugs, wires, coil pack, and crankshaft sensor. This is mildly frustrating to say the least.

I am going to disconnect the ECM for 10 minutes and let it reset, hoping that this is what is causing these codes.

LR Audi

Did you try replacing the spark plugs and checking the resistance from the wires/coils? I had had misfires starting on Cylinder #3 that eventually to all cylinders. I replaced all the plugs and I was good to go. Gained some fuel economy while I was at it.

The Stig

Yeah, I had done all of that with no luck. It ended up being a timing belt tensioner damper.

The only positive to finding this out after the fact was like you suggested, I ended up with a new ignition coil, plugs and wires which did increase fuel economy.

LR Audi

Good to hear that it all worked out for you, it's unfortunate that the timing belt tensioner was failing. However, if it completely failed then you'd be whooped for a new engine. Having to replace that part by itself and given the labour involved it might've been worthwhile to do the whole timing belt/waterpump service. I have to say that in my experience I've never heard of someone's timing belt tensioner failing as it's normal to replace it during your timing belt/waterpump service. Perhaps the last time it was installed it may have been a defective part. But it's good to be back on the road with your vehicle operating correctly. I'm surprised that this would cause a misfire code though, I really didn't expect that. I was thinking it would be more fuel/ignition related.

The Stig

I still had 50k before I needed a complete timing belt service so I opt'ed to just replace the tensioner. It's at 190k now, I'm not certain I will be driving it much past 240k or if it will even make it. Mechanic that did my timing belt/water pump/themostat service didn't actually change that piece out at 110k.

LR Audi

The technician definitely should have strongly recommended it, since you'd be paying only for the part itself and no extra fees for labour. It's actually one of the parts that needs to be replaced during the timing belt/waterpump service. It's like replacing the waterpump and leaving the original thermostat it.

Anyhow, when you do trade your car in you can go with a more fuel efficient 2.0T model that has much more useable power and is a lot easier to service than our generation A6. Our vehicles aren't actually all that bad, and amongst the 2.8 30V, 2.7T and 4.2 40V models our 2.8 30V is the most reliable. Gutless, but reliable. The 2.7T eventually requires turbo replacement and the 4.2 40V eventually requires the ZF 5HP24FLA to be rebuilt.

The Stig

I will admit to being surprised when I found out this piece wasn't replaced as part of the standard timing belt service, however I was given the optoin of doing a complete timing belt service when they diagnosed the tensioner damper as the problem. I declined based on the fact that I had been chasing this issues for a couple weeks and already spent about $1400 in the process and couldn't stomach another $1200. I took the cheap route and only spent an additional $600. I'll pay for it later, but hopefully at a time when this will be routine maintenance.

LR Audi

I don't blame you, I would have done the same thing. If you're mechanically inclined the timing belt service isn't too difficult of a job, although it requires the purchase or rent of specific tools. To do it the first time around will take about 4-6 hours but you would save a tremendous amount on labour costs. Again, this is only recommended if you plan on keeping your vehicle on a long-term basis. I'm still surprised that the tensioner would cause those codes. It is good to know that you're on the road safely though, but it is unfortunate that it had to come at such a considerable cost.