1999 A6 - 2.8 - Car runs great at cold start up for 5 minutes, then runs rough below 1500 RPMs then the CEL comes on - code P0303 ( cylander 3 misfire) and P0158 (o2 circuit high voltage) CEL flashes if i give it too much gas, so i have to drive using triptronic and shifting at high RPMs.

Thought it was the coil, pulled wire off plug and i am getting a good spark ( inserted screwdriver and held 1/4 inch off hood latch - getting a good spark.)


Can it be a bad injector? - How do you remove and check to see if it is bad?

please advise?????????????????????????

 

check to be sure your not leaking coolant into the cylinder. If it were a fuel or lack of fuel problem the sensor would not be reading high. But it could be that the injector is stuck on too. Pull it out and actuate using a 9volt battery so you don't fry it. You'll hear it click, You can also apply a little air pressure to it an blow it out while you actuate it. I cleaned mine by soaking just the tips in sea foam. If it doesn't click, it's not working.

I checked my cylinders to see if anything is leaking in there by inserting a suction tube through the spark plug hole when cold. Then I atach a hand actuated vacuum pump with the cup for bleeding brakes and see what comes out.

 

How do you remove the injector? Their seems to be a fuel rail running across the top of the 3 injectors on the side of the engine. Are they under pressure? do i need a special tool to remove them ( besides the star tool to remove the fuel rail?

Please advise

 

I would suspect spark more than fuel -- just based on experience with other cars. You might try swapping coils and see if the misfire moves. Then spark plugs. If it stays on #3, then fuel injector is next to check.

 

You cannot switch the coils on a 99 A6 coil. They are wired together and go to a harness coming into the coil pack. If you switch the wires, the firing order will be off.

How do you check the coil. ( their are 3 coils with 2 wires coming out of each one)

 

I agree it's probably a coil, but you never know.

Disconnect the fuel line from the rail, wrap a rag around it to catch the fuel.

Unbolt the fuel rail, and remove the vacuum line from the fuel regulator. Pull it straight up.

Before doing this stop in to your local Audi, BMW, Landrover dealer and pick-up a couple new injector o-rings they all pretty much use the same size.

When re-installing them lube the o-rings or they will tear. I use Vaseline.

Also make sure you put No. 3 Injector in a different cylinder. If the problem moves you'll know it was the injector.

At what point does it misfire??? all the time, start-up...or when?

 

Havent we gone through this a couple of times? I remember telling you how check the coils recently...

https://www.audiforums.com/forum/sho...d.php?t=140251

 

I know we have gone through this before, but since i do not have a gauge to check the spark output and the coil pack is one unit, is their a way to check the coil for a cylander 3 (PO303) on a 99 a6 2.8.

Please advise. - Also car runs fine when cold, after 5 minutes, the misfire starts occuring.

 

can anyone help me on this issue i have a 99 Audi A6 i get misfires on all bank one only misses at idle , and get codes p0300, p0301, p0303. p0302, i change coilpack which is one uni, plugs, did timing belt change cam sensor, one thing i notice is the plugs are geting soaked in gas, so i switch injectors to other side still get the misifre on all bank one and plugs still get soaked