Hello,

So, I recently bought a 99 A6 2.7T (AJK engine) that unfortunately have recieved way to little love over the last few years.
Before it was left in the hands of someone who clearly should've been banned from owning an Audi, the car went though a major transformation.
A few things that might be worth mentioning before I get to the problem:
- Rebuilt from tiptronic to 6-speed manual
- K04 turbos
- Downpipes, race-cat and exhaust from Dählback
- Upgraded intercoolers
- Intake and Y-pipe
- Giac chip



Anyways, when I bought the car the engine wouldn't run properly and 2nd, 4th and 6th gear was nearly impossible to reach. I thought it would be an easy fix, and the price was really good considering all the money and work that had been put into it by one of the previous owner. (The tuning, RS6 interior, valves, camshaft etc was replaced 5 years ago)


Got the car home and ran vagcom..
Ended up fixing:
- Crankshaft position sensor
- MAF (Didn't solve the problem.. Turned out to be the connector)
- Sparkplugs
- Tightening a loose plate under the gear lever fixed the problems with gear shifting.
- And obviously a regular service

The car has been throwing these codes ever since I bought it, and neighter of the repairs I've done fixed it:
- P0300 - Random/Multiple Cylinder Misfire Detected
- P0301 - Cyl.1 Misfire Detected
- P0302 - Cyl.2 Misfire Detected
- P0134 - O2 Sensor Circ.,Bank1-Sensor1 No Activity Detected

Using vagcom I checked the misfiring and cylinder 1&2 will misfire a hundred times in maybe 7-8 seconds. Cylinder 6 misfires occationally, so I think thats the one throwing P0300.

I tried swapping the ICM modules but it didn't make any difference.
Then I swapped the coils to see if it would move the misfiring to the other cylinders, but no..
Sparkplugs are brand new and they do get wet on the cylinders that misfire.


Any ideas would be appreciated

Yes, I did search the forum and read a bunch of posts without getting any closer to the answer

 

I would check out the injector(s) for those cylinders and then from there start looking towards the intake / exhaust values causing little to no compression.

 

I was going to say what Nabu said. I would go in this order. First go rent or buy a compression testor and check to make sure you have good compression. This would be the easiest and fastest of the tests to perform. IF your car had timing belt issues under a previous owner it is likely that you have a bent valve or two. Next I would check to make sure your fuel pump is pushing enough pressure to fire the injectors properly and check the injectors. Then i would check your vacuum lines and vacuum soliniods to make sure all that is working right.

 

Thank you both for replying
Did a compression test today and got 0(!) compression on the cylinders that is misfiring, while the other 4 is stable at 160-165.
Clearly there is something terribly wrong with cylinder 1&2. What are the most common failures that would cause this? Since I got absolutely no compression at all on those 2 cylinders I'm thinking the valves must be jammed open some how :/

 

I am sorry to say that 90% your problem is bent valves. If two are bent to 0 compression several more are likely bent a little also. Your most likely looking at complete head jobs on both heads. You could try to shortcut the job and just do the one head that has the bad cylinders in it but I would not suggest you do that. If you want to do it right your looking at $2500 to $3500 depending on the machin shop and how much they want to charge you. I got lucky, or so i have been told, and mine only charged me $1500 for two complete head jobs and all new valves. I hope I am wrong.

 

There is one more test you could do to be sure but the outcome would not reduce your repair bill any. You can pour a little oil into the cylinders that are bad and run your compression test again. If you get any boost at all in the result it could mean that rings are the problem. The other test is a "bleed down" test. YOu pressurize the cylinder with air and listen...If you hear air hissing out of the intake manifold then you know its intake valves that are bad. If air comes out the dipstick and or the crankcase breather then its rings and if it comes out the pipes its exhaust valves. The result still means that both heads have to be pulled and tested anyway.

 

Happy new year fellas.
I finally have some updates on this matter (The car's been standing still for some months now, but it's finally time to get back to fixing it ) Sorry for the long wait btw..

Turned out the wiring to MAF was broken making it go on a really rich fuel mixture, causing O2 sensor to fail.
These combined most propably made quite a lot of heat in the cylinder areas on that bank, causing the spark plugs to fail.
I found that 2 spark plugs have disintegrated leaving debris inside the engine (The insulation cracked into pieces and fell inside the cylinder, to most likely be crushed against the valves and jamming some if not all of the valves on those 2 cylinders.) Thankfully this is on one bank so I'm hoping to get away with just one head job.

Inspected the piston and cylinders as well as I could and it does not seem to have made any damage to either of those, leaving valves the most likely issue here. Then there is the question of turbo's.. I don't know just how crushed the porcelain insulator would have been, if it in fact got crushed against the valves. Might have to replace the turbo on that side if the porcelain bits were big enough when they passed though, if they got that far.

Btw, the local audi shop estimated 9k-10k USD for a complete heads job including labor