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Mk4 Golf AGU misfire when hot and at low revs/idle

9056 Views 6 Replies 4 Participants Last post by  markpalmer
Hi everyone,

I have recently noticed a bit of a misfire on my AGU 1.8T when the engine is up to temp. It would only last a few seconds at low revs (ie 30mph in 3rd 40mph in 4th etc) but then clear itself over 3000rpm. However, driving to work today it started misfiring constantly and would not clear. I pulled over and disconnected the coilpack plugs one at a time. No.1,2 and 3 made it alot worse but No.4 made no difference = misfire cylinder 4. I swapped coilpacks 3 and 4 but still had the misfire on cylinder 4. The same with the plugs, swapped 3 with 4 and the misfire is still on No.4! There is fuel from all 4 injectors too but this was only a visual check. I called the AA and they had a look. No fault codes present. He said he would put it down to a mechanical failier ie follower sticking, valve problem etc etc. But surely this would mean the car would misfire all the time and not only at temperature, right? Any ideas?

Now the car has cooled down again there is no misfire!?!?!
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Ignition Amplifier by the sounds of it, mine went in the same way. its a little unit bolted to the back of your airbox with electrical connections either end.
Cheers Nizturbo, I'll take a look!
Definitely the ignition amp, though it's a pricey part, mine was over ?100 if I recall correctly..
All sorted! The breather hose from the bottom of the inlet manifold was split and the fuel filter was dirty. Replaced these two and its running fine again!
that wouldnt make it mis-fire, it will be your ignition amp. mine does it every now n then.. but it aint worth replacing yet as it only does it once in a blue moon when driving round town n its really hot..
As mad as it sounds, its been fine ever since! Mine was missing every time i drove it. It was an Audi Tech who sorted it. Apparently this engine type suffers with misfires when the fuel filter gets clogged up = fuel pressure drop!? He had the car for 2 evenings and only charged me £30.
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