A3 8L 1.8T Limpmode / Missfire?

reptor245

reptor245

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hey guy, just drove my car and all was ok, then after about 2 miles its gone into limp mode. (severely misfiring / juddering) I managed to get it home and run Vag-com on it with no fault codes.
Ive tried cleaning the plugs, maf, connectors the the ignition module with no change. I did notice some unburnt fuel on plug number 3. Was just wondering if a coil pack would cause it to be in limp mode rather than a misfire?
Any ideas please
 
I am assuming its an AGU? if so then its likely to be the ignition pack

<tuffty/>
 
Yeah its a agu. Was wondering how to check for sure before I shell out money on something it might not be.
coil 3 has like a burnt mark on it (might not be but looks like it) also would a coild pack make it rumble really bad on idle too
 

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swap them around and see if the misfire follows the coil pack

<tuffty/>
 
How can I tell if it follows it around? I swapped 3 and 2 and still in limpmode (heavy juddering and popping) can smell fuel a bit too from exhaust.
 
Thats not limp mode... that's just something is broken mode... swapping it like that won't fix the issue...

To test which cylinder is misfiring pull the injector plugs one at a time (replacing as you go of course)... if the engine note doesn't change then you have found the misfiring cylinder...

To test if its a coil pack (unlikely as its almost always the ignition amp and ironically cyl 3) then swap the coil pack on the misfiring cylinder to one that doesn't and repeat... if the misfire is now on the cylinder you fitted the suspect coil pack to then its the coil pack... if its still on the same cylinder as before its the ignition amp

<tuffty/>
 
Injector plugs? Never done that before. Is it easy to do? I did have same symptoms ongoing for year's now you mention it to do with the ignition amp. I found if I clean the connectors it cleared the issue
 
Injectors will have wiring plugs on each one... metal clip facing the cam cover needs to be pushed in and then lift the electrical connector... these are normally aired together with a bit of plastic so don't yank/pull too hard... you only need to lift it enough to electrically disconnect the injector while the engine is idling..

<tuffty/>
 
Update. I had a spare ignition amp for a audi a4 I bought in error. Bigger fitting to the air box but same connectors. Just plugged it in and problem solved. Thanks tuffty for talking me through some steps :)
 
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