Bad times.... (Audi A3 1.8t-agu)

Points
30
Location
Suffolk
Car
Audi A3 1.8T-Sport
So.... I'm driving along at about 40mph and my car decides to run on three cylinders, then two, then three etc.
I pull up at the side of the road and it dies, it won't restart.

I get it recovered to my mates workshop where we swap coil packs (number two isn't sparking) and crankshaft sensor (as we had these to hand) to no end.

The computor doesn't come up with any faults and there are no warning lights on the dash.

A compression test sees me sweating profusely....
Cylinder one-100, cylinder two-40, cylinders three and four are both 90.

The cambelt and camchain are both tight and cams don't appear to be broken (all turn as they should on the starter).

Head is coming off tomorrow.

Bad times.
 
Lets hope it is something simple like a dead spark plug or faulty ignition lead. My first guess would have been a coil pack but I'm guessing this didn't fix it.
 
Lets hope it is something simple like a dead spark plug or faulty ignition lead. My first guess would have been a coil pack but I'm guessing this didn't fix it.

We checked/replaced all coils and plugs to no end, still no spark on 2. Its the lack of compression on 2 which scares me :confused:

I'll know more tonight when we whip the head off. I'll keep you posted.
 
Please do. If I ever needed to get a head for mine I would go to CNC and get a +1 oversize exhaust port done as well as their usual flowing and porting.
 
before i wip the head off i would find out why you dontt have spark to no.2
is it the pencil coils you have or is it 2 coil packs
1&4 2&3
if the 2 pack does no.3 have spark if it does new not 2nd hand pack if that still no good
then got to look at the wiring got to be a cut in the wire somewere or the wire is no good it self

then look at the compression
put a small bit of oil down the bore if you get good compression then its the rings
but need the spark
 
Obviously you have to get a spark for that cylinder.

@ Lutonmatt - if the oil does not improve the compression reading then is it possibly a sticking valve stem or tappet? Perhaps one of the valves has accumulated carbon deposits and is not seating properly? These are 5v per cylinder engines if I remember correctly and can be prone to buildup of 'gunge' if they not running perfectly.
 
that it can be
i alway put a little bit of oil if it is low then it rules out the rings and then only leaves the valves or stem seals or even the head gasket not not very likey that

just safes doing half a job then the customer saying i dont have the money to do the rings
 
luton its individual coil packs, and i think the AGU have an separate ignition amplifier as well that supplys the coils.

im surprised that its not showed a fault for the spark but again its an earlier engine
 
i would of thought it would of showed a code as well
had a golf in the other week got one of the other chaps to service it then it come back next day with a miss fire and the light was on

had a look and think what he had done was dropped the spark plug and cracked the cermaic causing the spark to jump out of the side of the plug
ecu loged it on a a missfire

but if it has pencil coils they are comman to go
did not know they had separate amplifiers
 
Ok.

The state of play now is as follows:

Head is off and all valves and pistons look fine, im having it all thoroughly checked out today.

Still not sure whats causing the lack of number 2 spark. Its not the coil or the plug.

Will update again tomorrow.
 
Removed all the valves last night.

All buckets look good, valves are all slightly cokey and pitted but nothing more than you'd expect on a car with 92k on. All will be thoroughly cleaned and valves will all be reseated.

The spark issue. Im going to fit a new camshaft position sensor and the ignition sub-harness just to rule those out. I obviously won't know if this has worked until i fire it up with the shiney clean head back on lol.

Typically this has all come at just the right time.... As im about to sell the car....

I need something more practical, sad i know. I need more doors and a bigger boot so my little silver rocket skate must go. Someone is going to get a bargain though, full audi service history and just had full service and top end rebuild!

Anyways, will update when i have more news.
 
RESULT!

Me and my mate were in the workshop until 23:10 last night and back down there again at 08:30 today.... It was worth it.

She now runs and drives absolutely beautifully! YES!

We're still not completely clear on the which of the contributory factors was the final straw but its all sorted now and driving better than ever. My theory is this; all the valve stem seals were worn and all the valves were a bit pitted and cokey. Number two's stem seals were worse for some reason which lead to it's valves being a little more coked up than the others. Eventually number two decided enough was enough and lost all compression. I still have no clue as to what caused the loss of spark to cylinder number two but its perfect now.

So! She's had a full top end de-coke and rebuild with new seals and gaskets throughout and is now spot-on! As im thinking about selling her i refitted the origional airbox and blanked off the BOV's trumpet (its a splitter).

Anyways, i hope you've all enjoyed my little unexpected half-term project :)
 

Similar threads


Please watch this on my YouTube channel & Subscribe.


Back
Top