Hi all.

I have a 97 A6 Quattro 2.8v6 AFC.

I rebuilt the top end due to the rad blowing and the motor overheating. It's had a new rad, full top end gasket set, timing belt kit, head bolts, cam position sensor, water pump, thermostat, spark plugs, air filter, oil/filter, transmission fluid/filter, stub mount and brake fluid that I can remember.

The car was running ok (besides blowing all its coolant out of the exhaust) before I tore it down. I stripped the heads down and had them skimmed and had the valves reseated.

I now have it all back together and 4, 5 and 6 are misfiring. I have checked evening I can think of and evening I could find to check on here.......

 

I tested the fuel injectors with a multi meter (all within normal parameters), put my multi meter on the injector leads (reading voltage, but my meter is not fast enough to show the pulse), swapped the plugs, leads and injectors over from the other side, triple checked (with the correct tools) that the timing is correct, checked ask the connectors are in the correct place, checked all the vacuum hoses are in the correct place. I also checked the compression on all the cylinders today. 160 psi was the lowest, 170 psi was the highest.....all normal.

After all this, 4, 5 and 6 are still acting up. It idled fine for about 30 seconds, twice today but then went back to misfiring.

I've searched on here but found nothing like it, but I got a few of the ideas to try in the process.

If it was the cam position sensor, surely if that was bad then all the cylinders would be playing up?

Also, if it was fuel, then again all cylinders would be acting up.

I'm running short on things to try, so I'm hoping someone might be able to point me to my next test to try.

Thank you for any help I can get.

 

It could be the cam sensor - there's one per bank of cylinders. Could be your driver side sensor is acting up, although the V6 engines can and will run with one bad CPS, since the engine can read the crank sensor and one cam sensor and infer timing on the opposite bank.

What did you do to verify your timing setup is correct? It sounds an awful lot like bank 2 is off.

 

My car only has one cam position sensor and I used the timing bar and crank pin to set the timing. I've had the idea that I'm going to spin the coil pack around and connect the ht leads to their respective opposite connections and see if the misfire jumps to the other side. I'm let you know how it goes.

Any other ideas of things to check are most welcome.

Also, if the timing was off, it wouldn't run good for a few fleeting moments. It would just simply run bad.

Here's a link to to a short video I was taking of it running good, then not.

http://vid1154.photobucket.com/album...810_194719.mp4

Also, my apologies for the typo's I'm on my phone and the auto correct makes me look like an idiot!

 

Well, that's another avenue of thought ruled out. It's not the coils, the igniter box or the MAF sensor.

I took the coils and turned them around in their bracket and bolted it back in place and started the car. 4,5 and 6 are still misfiring. Any changes would have ment coils or igniter box but no.

I also tried disconnecting the connector to the MAF and the engine just stopped.

Like I have said earlier, I know it's not the injectors because I have swapped them over to the other cylinders with no change. Also when I disconnect one of the misfiring injectors, the motor misfires a little less and struggles even more to run.

I put the new cam sensor on this morning also with no change.

This is very frustrating.....

 

I plugged in a generic code reader after pulling and reconnecting a load of connectors to listen to the motor, and not surprisingly I had 18 codes waiting for me!!

After clearing those and running for a few mins the only codes to show again were
P1106
Feeze frame Data
Fuel sys 1 OL fault
Fuel sys 2 OL Fault
Engine Load 2.7%
Temp 177*f
STFT B1 32.8%
LTFT B1 0%
STFT B2 32.8%
LTFT B@ 0%

followed by p1101 (drivers side O2 sensor.

I also checked the tightnes of some of the bolts on the intake housing and noticed that some were not very tight, so fixed that, but made no difference.

I also had an earlier misfire code P0300
Freeze Frame Data
Fuel sys 1 OL
Fuel sys 2 OL
Engine Load 5%
Temp 78*f
STFT B1 0%
LTFT B1 0%
STFT B2 0%
LTFT B2 0%

followed by P0304/5/6

A dodgy o2 sensor surely isn't going to cause this misfire is it?

 

I also found some loose bolts holding the intake housing down but tightening them made no difference to the misfires.

I've had someone from another forum suggest that I remove the upstream o2 sensor to check if the cat is clogged. Though a clogged cat wouldn't cause misfires would it? Wouldn't it just choke the bank in question?

 

Is it possible a big *** vacuum leak could be the culprit?

 

check your ignition module/modules. in my A8 there are two, one per cylinder bank. there's a easy how to check it instruction somewhere out there.

 

There's only one on my a6 and I'm sure it's fine BUT I'll try anything right now. I'll look for the “How To" tonight.