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iauto8
iauto8, ASE Certified Technician
Category: Audi
Satisfied Customers: 137
Experience:  15 year ASE Auto Technician. European import specialist.
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Audi A6 Quattro: 2001 audi a6 misfiring on cylinders 4, 5,6

Resolved Question:

2001 audi a6 misfiring on cylinders 4, 5,6 replaced engine coils..replaced spark plugs and still get same reading misfiring on cylinders on cylinder 4,5,6 there is no gas smell either. what do i need to fix to solve this?
Submitted: 2 years ago.
Category: Audi
Expert:  iauto8 replied 2 years ago.

iauto8 :

I will post test procedures for missfires on the same bank. I would check cat first. To check cat without exhaust back pressure gauge, just remove front o2 sensor on that bank and run cat to see if it runs better. Chris......

iauto8 :

 










1. Inspect spark plugs, coils, connector plugs and wiring harnesses for correct connections.

2. Check timing belt tension and use Audi special tools 3242, 3391 to verify that timing belt is set correctly.

3. Perform a compression test. Specification 131-203 PSI/9-14bar warm.

4. Remove valve covers and inspect timing chain tensioner and alignment.

5. Perform cylinder balance test on injectors by disconnecting individually, or clean injectors.

6. Perform exhaust backpressure test using a gauge, maximum pressure should be below 4 PSI/28kpa at wide open throttle load driving.


Customer:

do you think that o2 sensor on the 4.5.6 bank is what could be the problem? i've already done most of the steps u listed except for the timing chain tensionor and alignment and i still keep getting the same misfire code on cylinders for 4 5 6 and the car is still misfiring u can feel it out the exhaust. the exhaust back pressure test came back at 2psi. my next step is to replace the o2 sensor on that bank. and the diagnose pc said something about the o2 sensor and referencing cylinders 4,5,6 at the store i took it too and on the dash the brake lights keep flashing but when I pull the emergency parking brake up then it stops flashing but as soon as I put the emergency brake down it keeps flashing

iauto8 :

The o2 sensor could be the problem. However I also would see if it runs better with the F-o2 sensor removed. Was the exhaust back pressure 2psi @ idle. If it was that is way too high. Should only be .5 psi or less @ idle. I think the catalytic converter is clogged. Chris.....

iauto8 :

I will be offline for the rest of the evening. I will check to see if you have more questions in the morning. Thanks. Chris....

iauto8 :

To verify exaust back pressure you may want to check other bank to compare as well. Chris...

Customer:

yes the 2psi test was done by the store and i believe it was at idle, and in regards XXXXX XXXXX brake light flashing in the dash would that be unrelated? so i should also check the catalytic converter after i replace the o2 sensor or should i do the catalytic converter before replacing the o2 sensor

iauto8 :

I would check catalytic converter before replacing o2 sensor. The brake lamp would be unrelated. Does the brake and ABS lamp flash? Chris....

Customer:

the abs light is on but its not flashing, but the brake light keeps flashing but the light stays on and steady only when i pull the emergency brake up. how do i go about checking the cataytic converter and what would defined as clogged or what am i looking for?\

iauto8 :

To check the cat you can run car with f-o2 sensor removed and see if it runs better or verify back pressure test. The spec for back pressure is a guideline because you have a 2 bank exhaust system I would check one side against the other. If one side has higher back pressure that side has a clogged cat. The ABS system would need scanned to see problem. Common problem with that system is a failed ABS control unit. It is normal for brake lamp to stop flashing when parking brake is on. Chris........

Customer:

we determined it was the timing chain tenisoner shoe pads one of the pads was chipped and how would we be able to turn the camshaft so that the chains fit correctly?

Customer:

or lined up

iauto8 :

In order to properly service the cam shaft adjuster the cams need to be removed. The timing belt will also need to be removed to do this. There are a few specialty tools needed to properly align the timing belt as there are no marks on the cam gears. Chris.......

iauto8, ASE Certified Technician
Category: Audi
Satisfied Customers: 137
Experience: 15 year ASE Auto Technician. European import specialist.
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iauto8
iauto8
Audi Mechanic
137 Satisfied Customers
15 year ASE Auto Technician. European import specialist.