can anyone help i have a 99 a6 1.8t auto it has a missfire on no1 cilinder at low revs above 2500rpm its seems fine it has plenty of power when driving
at tickover you can remove no 1 lead with no change to running so i dont think it is fireing the ecu has been checked as has the plugs coils timing chain compression and a smoke test done throttle body has been cleaned and ignition amplifier has beed checked and the injectors cleaned and checked all with no change to the running its starting to get very expensive can anyone help

 

If you are saying that removing plug at idle does not make the car run any different, then obviously you are not getting any spark to the cylinder. So I understand you check the plugs and coils? How did you check it? Did you check the plug caps?

I would just switch the coil, plug, and plpug cap from any other cylinders to no. 1 cylinder and see if the no. 1 cylinder runs again. If it still does not run, then it is probably wiring related.

 

Check the ohms of each fuel injector. When was the last time you changed the fuel filter? Is the problem intermitent? Is it only the #1 cylinder?
I may be the fuel injector, the ignition, an air leak, etc.
For air leaks, they spray the outside of the intake manifold with a chemical which causes the idle speed to drop if there is a leak.
However, a plugged fuel filter or weak fuel pump could also cause a misfire. There is no easy way to measure the fuel pressure on an Audi with a fuel pressure gauge.

 

we swaped the plugs and coils with no change it is always no 1 the only thing we have not changed is the wiring as looks like changing the whole loom do you think a bad earth migh be the problem or a slightly broken wire?

 

Well if the plugs and the coil checks out, then the only other thing related to electrical is the wiring. Also a6hcw has some good points. It could be the injector. Or other possiblity is the head gasket. Have you check compression on all cylinders?