xips069

Hello I just picked up a 2001 audi a6 2.7t with 188000 miles and have codes p0300 p0741 p0421 I'm seeing lots of different answers for what some of the codes could be caused by and wanted to post asking if any of the codes could cause the other codes to be thrown. like for p0421 I seen a post saying it could be the o2sensor and another post saying it could be the cat. p0741 says it has to do with the trans that's not where my main focus is right now I want to get this running with out the misfire. Right now it will start and run but its not running on all 6 and it seems to stay that way all through the rpms. I do notice a coolant smell but not seeing any coming out. And my temp is not going past half way. on a 40min drive my oil temp was at about 225. If you guys can point me in the right direction for getting this thing running correctly that would be awesome.

SloopJohnB@mac.com

Std problem with turbo and many engines is vacuum and or boost leaks. Find and fix.
Clean engine and look for coolant leaks.
Check for maintenance records on when TB was last done. If more than 5 years or 90K consider doing it if you're keeping the car for more than 30k miles...

xips069

That would make it misfire to?

ddillenger

Pull the coil packs, check to see if the sparkplug holes are full of oil.

xips069

Ok I pulled the coils and checked the compression its consistent right around 170 165 175 all close together. 2 out of the 3 cyl on the driver side had small amount of oil in them not much at all. The passenger side did not have any oil in them. I did swap the coil packs from one side to the other and it did seem to run a bit different. The main thing I noticed was that there is water vapor coming from the passenger side rear corner of the engine looks like right by the valve cover. Is there any thing back there that would be letting coolant out? Or is this most likely a bad head gasket?

xips069

O also there's oil in the intake system all the upper tubing past the mass air flow sensor.

SloopJohnB@mac.com

Were any of the plugs bright clean indicative of a head gasket failure/leak? Are you losing coolant? If the misfire moves with the coil moves then you have a bad coil. Otherwise keep looking.

jseklund

If you remove the accordion tubing between the airbox and the Y pipe, and look straight down you will see a temperature sensor for the coolant in a pipe that goes between the heads. If you see dried coolant around there, that's you're leak. Since you are not loosing coolant at a fast pace, that would be my first guess. My second guess is cracks in the coolant resevoir, third spot would be the auxilary pump under the intake manifold, fourth would be the waterpump/thermostat.

The CTS could cause misfires and possibly the O2 sensor code. It's less than $30 and takes 30 minutes to replace. They go bad quite regularly.

Pull each coil pack and check for spark. Spark issues could be caused by spark plugs, coil packs, or the POS. You really need to try to narrow the misfire down to a cylinder. If you've got spark, I would pull the injector rail and make sure each injector is firing.

And as stated above - look for vacuum/boost leaks.

As stated above, you really should change the timing belt if you are not 100% positive of when it was changed last.

Finally, one more item that could tie all of these together is a bad MAF - but I would save that for more diagnosis.

xips069

Ok so I replaced the spark plugs and two coil packs both the front ones left and right side. Car still having a mis. So I thought I would go to aamco and have them chevk codes with there code reader. I have a lot of codes. Lot more then autozone gave me. Here we go.
P1458
P1624
P1176
P1131
P1602
P0741
00532
01212
65535
P1296
P0421
P0431
P0300
P0304
P0306
P0303
P0305

Damn that's a lot of codes.

SloopJohnB@mac.com

Clear them all out and try again.