Missfire Diagnosis - Running out of options HELP......
I have a 2.0TFSi Quattro that has a mild missfire between 1700rpm and 2500rpm. Although it is less noticable at above 2200rpm and never noticable above 2500rpm.
It's only on very light throttle and any deflection in throttle angle causes the missfire to stop.
25% throttle or full throttle pulls, through from 1200rpm, are smooth with no cough's or misses at all.
I am however running out of options......so far I have fitted/done the following :
New DV (old one had a split diaphram)
New Coil Packs
New HPFP Cam Follower (old one was pretty much OK)
No sign of cam wear when changing HPFP follower
Diagnostics report 700-720psi fuel rail pressure at Idle and upto around 1500+psi at other times (monitored before the HPFP follower changed)
Throttle pedal was removed and stripped/cleaned with contact cleaner. There is some adjustment on the pedal so this was set to the max amount of adjustment available. It made a noticable difference to performance, as it clearly wasn't get full throttle. However, the missfire was still present at shallow throttle angles and at the same rpm as before. The throttle was then reset to the original position and full throttle was regained, and missfire was no different.
Fuelling check using Innovate LC-1 Lambda in exhaust shows nice steady 14.7AFR at idle and cruise and up as rich as 11.6AFR at WOT / high Rpm.
During cruise there is no deflection in AFR (logged using Innovate LogWorks) noticable during missfire events
Missfire is still present with Lambda removed, although ECU default fuelling is a touch leaner, being between 14.7AFR and 15AFR.
Monitoring boost/vacum and the missfire always occurs at -15 To -20 in/hg vacum. Outside of this range it appears OK.
Boost appears to be about 11psi dropping to about 5psi at high rpm, but I want to log this again with an analogue gauge to confirm.
Car has covered 89,000 miles with Full Audi Service history and is very clean and well looked after by it's previous owners (I've only had it 3 weeks). I was suprised how good the HPFP follower was after seeing some on here and other interweb images.
Any help would be much appreciated......