Help needed with 2.7T misfire problem - PO300 - Audi Forums
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post #1 of 9 (permalink) Old 08-17-2009, 01:39 PM Thread Starter
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Help needed with 2.7T misfire problem - PO300

Hello,
After 35k miles (total of 79k on the car) I am having my first real problem with my 2004 Allroad that I cannot seem to easily solve.

I have been having a heck of a time with this issue. My car started acting up last Friday on the drive home. By that, I mean you could feel sudden misfires and lack of power. Feathering the gas pedal was the only way to got it home.

1) Pulled all spark plugs - all were beige and clean. Changed plugs while in there and also added some drygas to the tank just in case water got in there.

2) I pulled codes - got 306 initially. Swapped cyl 6 Coil with another cylinder, cleared codes. Test drive was 5 minutes and the problem started to "feel" worse. I rescanned the car and now found codes 300, 301, 303, 304, 305 and 306 - all but one were misfiring.

3) Getting worried, I removed the timing belt cover. I could not see any visible signs of trouble. The belt appeared to be fine.

4) I changed the Fuel filter. When the nut was cracked loose, serious pressure forced some fuel out. Not a valid pressure test but a good indicator. No improvement on next startup.

5) I pulled one plug from each bank and ran a cranking compression test. Both sides still have 120PSI.

6) I unplugged the cam timing sensor on the Driver side. No change in behavior other than the expected code of 020.

So, I think I have ruled out injectors, coil packs, fuel filter and plugs for sure. Things now may get expensive.

One more thing. The car idles badly now too. The engine shakes visibly in the engine compartment. Again, all the plugs where clean after limping home and before changing them anyway. This same problem occurs when the car is cold or warmed up so guessing it is not an EGT sender or O2 since both take time to heat up.

I tried calling Audi of Nashua to see if a tech would be willing to spend just a few minutes with me. I was almost floored when I was told that the techs were busy trying to make a living and that they do not like to give advice for free. After that, the service rep said he'd see if he could talk to someone for me. They have not called me back and now I would not take my car to them ever again.

The day the problem started was also one of the hottest days of the year out here - not sure if this could be a clue or if it could have contributed so sensor failure.

Any thought or ideas would be much appreciated!

Thanks!!
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post #2 of 9 (permalink) Old 08-17-2009, 04:44 PM Thread Starter
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Update:
I contacted the gas station to see if anyone else had problems. They referred me to the supplier who said that their gas comes up from Boston and has the maximum ethanol content in it only as of lately (full 10%).

I was able to limp to a different gas station 4 miles away. I added 13 gallons of super unleaded fuel just in case the gas was bad. On the 4 mile return trip, there was no difference noticed. Either lots of fuel is making its way into the exhaust or the car is running terribly lean and heating the pipes. The exhaust was so hot under hood that I thought a fire could ignite. The plugs do not suggest a rich condition as one would expect with misfires - they actually suggest a lean one??

I pulled the codes again and got 300, 302, 304, 305 and 306. 2 and 5 are known to have good compression (120 psi).

I measured the passenger-side cam sensor with an ohm meter and found 16 ohms. Not sure if this is normal or not. Unplugging the sensor caused the same behavior which makes me wonder if this has ruled the sensor as the problem out? The passenger side sensor seems to be different - it has three wires. I did not attempt to measure it.

As expected, Audi of Nashua never did call me back. I just don't understand how they can stay in business treating people the way they do.

I am about out of things to test/try. Anyone have any ideas?

Marc
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post #3 of 9 (permalink) Old 08-17-2009, 05:09 PM
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Talking audi of nashua

Yeah i here you on that one. I was going there too. But about 5 years ago i stopped. because they made me fix somthing that should of been done for free(recall on a4 control arms). It costed me 2000$. So i took it to audi of america. You know what they did. They mailed me a check for 187$ and said that what it would have costed for the recall. I was never so insulted. After this s4 i will never buy another audi again. My 1st one i had for 7 years and i had over 40,000$ in receipts thats more than i paid for the car itself.
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post #4 of 9 (permalink) Old 08-17-2009, 07:12 PM Thread Starter
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Man... sounds like I made the right call to stay away from Audi of Nashua! Sorry to hear that it has turned you away from an otherwise great car! They are not the easiest things to work on for sure.

So another test is done and the mystery is growing. I cut the fuel supply line and installed a brass T. I had a mechanical VDO gauge hanging around so I installed it for now and fired the car up.

The Fuel pressure is a solid 55PSI. Could this be too much? I would have thought it should be lower at idle? Anyway, as the engine shakes at idle, the fuel at the rails is a nice constant 55PSI. I tried loading it up for a second in drive and it did not move. I guess it would have if the turbos spooled.

This now seems to rule out the following?:
-Failing Fuel pump/regulator [55PSI at idle. Is this about 10PSI too high?]
-Fouled Plugs [changed all 6. Before change, all 6 were clean and grey/beige in color]
-Bad Fuel [added 13 gallons of fresh 93 octane, drove 4 miles on new fuel]
-Clogged Fuel Filter [changed it]
-Compression on 2 and 5 fine. Did not check remaining yet.
-Faulty Ignition Coils [misfires on all but 1 and 3 and all of the sudden. Plugs clean]
-Slipped Timing Belt [tested cyl 2 and 5. Both 120 PSI at slow crank speed. Belt appears visually ok]
-Bad Injectors [Assuming too many cylinders misfiring all the sudden to be cause?]

Current Condition:
-Rough shaky idle
-no power. Feels like misfiring for sure including vibration associated with misfire
-plugs were all clean. Have not rechecked all since changing them the other day though
-Extreme heat under hood after test drives (concerning for many reasons including cat damage/fire potential)
-Codes 300, 302, 304,305, 306
-Condition actually worsened over last day's tests. Feathered throttle to get home when issue started. Car made enough torque at low RPM to drive home. No longer the case and higher RPM needed to drive without feeling like engine is taking a beating from vibration.

I am not sure where to turn to next. The driver side CAM Position sensor (Hall effect?) measured 16 ohms. When disconnected, code 020 appeared as expected. Is there a test for these? Anyone know if they could they be the cause?

The engine does not appear to be commanding enough fuel from the injectors. It sure just seems VERY lean given high temps and clean/consistent appearance of all plugs.

A suggestion was made to disconnect the battery for a while to reset the computer. I have not tried this as I am concerned it could throw me off track as I cannot easily drive the car in the current condition to allow it to re-learn params.

Open to any/all ideas - I am running out of them!

Marc
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post #5 of 9 (permalink) Old 08-17-2009, 11:37 PM
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2.7t

The sensor your talking about is the cps (hall sender) witch is in betweem the fire wall and the rear of your engine. You have to have real thin arms to sneak in though. And make sure you take the metal spacer bracket off the old one.
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post #6 of 9 (permalink) Old 08-18-2009, 07:29 AM Thread Starter
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That figures - I can't really see back there. What are the two sensors on the front of the cams for? Seems crazy to put a sensor on both the front and the back!: confused:
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post #7 of 9 (permalink) Old 08-19-2009, 08:02 AM Thread Starter
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Does anyone have any ideas?

How likely might it be that the CAM sensor is bad? The PCM reports that all cylinders on the driver's side bank misfire. Only one on the passenger side shows misfire. This has been consistent after clearing codes and test driving.

The timing belt is 4k past recommended service. It really appears to be in great shape however.

The issue occurred after shutting the car off for 20 minutes on a very hot day and after an hour of city driving. Heat seems to be a factor if that is a clue.
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post #8 of 9 (permalink) Old 08-19-2009, 03:14 PM Thread Starter
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Talking Misfile issue resolved

If you can believe this, two coil packs failed on the same trip home. Numbers 2 and six both failed and this showed misfires on 2,4,5 and 6. (It was 90+ degrees out that day and I am sure heat was a factor)

$90 later and the car is running 100%. What were the odds of loosing two coils on one 70 mile trip? Can't image they'd be very good.

The way we found out where to start is as follows. Clear codes, start car, read codes and look for first misfire report. Repeat process. Number 2 came up first each time.

We replaced #2 and repeated process. #6 came up first each time. Replaced #6, went on test drive and no more problems!
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post #9 of 9 (permalink) Old 05-17-2013, 08:57 PM
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Wiring Harness is TOAST

I changed:

1) Both EGTs
2) All 4 02 sensors
3) All new NGK PFR6Q plugs
4) All new Beru Coil Packs(6)
5) All new ICMs

And the car still had a cold misfire, at startup and when restarting it, after running. Wiring harness is always subject to heat cycling and will eventually get brittle and crack apart. Ready for a 13 hour job?
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