A3 3.2 Intermittent Misfire
Discussion
So, I’ll try and keep this brief, but it’s become a bit of a saga.
I missed my mk5 R32, so picked up a 2005 A3 3.2 cheap from the auction (I know, I know). It’s always had a slight hunting issue at idle, but only when warm. No engine light on.
The problem got more common, so it went into an Indy garage who had a theory that the car had forgotten the “closed” position of the butterfly valve in the air intake. They reset something and the problem went away for a month.
It then creeps back in, gets progressively worse, I squirt some intake cleaner into the air box and the problem goes again for a week before it comes back with a vengeance. Engine light, misfire at low revs, having to keep the revs up to make it driveable.
Booked it into a local garage, they try a coil pack before realising the misfire was moving around the cylinders. They admit defeat but rule out the coil packs.
I book it into another VAG specialist who now tell me that it’s the timing chain stretched because blocks 208/209 are reading blank, therefore out of measurable range.
I took that on face value, but I’m now doublethinking this...
The fault is still intermittent and not when cold.
There’s no loss of power.
There’s no rattling from the engine.
The block 208/209 measure thing is debated widely about whether or not it’s an accurate measure of timing chain stretch (and in any case, their machine didn’t actually provide a value, just blank boxes “suggesting” that the positions were outside of readable limits).
The money light hasn’t been triggered by a cam/crank position mismatch; it’s only been triggered by the misfire.
I am now thoroughly confused. Has anyone had this experience? It’s only on 112k miles. I’m loathed to splash out on a new chain anyway, let alone with confusion around how the diagnosis was reached.
I missed my mk5 R32, so picked up a 2005 A3 3.2 cheap from the auction (I know, I know). It’s always had a slight hunting issue at idle, but only when warm. No engine light on.
The problem got more common, so it went into an Indy garage who had a theory that the car had forgotten the “closed” position of the butterfly valve in the air intake. They reset something and the problem went away for a month.
It then creeps back in, gets progressively worse, I squirt some intake cleaner into the air box and the problem goes again for a week before it comes back with a vengeance. Engine light, misfire at low revs, having to keep the revs up to make it driveable.
Booked it into a local garage, they try a coil pack before realising the misfire was moving around the cylinders. They admit defeat but rule out the coil packs.
I book it into another VAG specialist who now tell me that it’s the timing chain stretched because blocks 208/209 are reading blank, therefore out of measurable range.
I took that on face value, but I’m now doublethinking this...
The fault is still intermittent and not when cold.
There’s no loss of power.
There’s no rattling from the engine.
The block 208/209 measure thing is debated widely about whether or not it’s an accurate measure of timing chain stretch (and in any case, their machine didn’t actually provide a value, just blank boxes “suggesting” that the positions were outside of readable limits).
The money light hasn’t been triggered by a cam/crank position mismatch; it’s only been triggered by the misfire.
I am now thoroughly confused. Has anyone had this experience? It’s only on 112k miles. I’m loathed to splash out on a new chain anyway, let alone with confusion around how the diagnosis was reached.
Edited by JamesR32 on Friday 20th December 22:17
Normally if you've no reading on blocks 208 or 209 this would indicate a sensor fault. If they were stretched that far out of limit your hear a lot of marble in a tin can noise. Have you checked blocks 90 & 91 you want these as close to 0 as possible. If there out I believe this is then a timing issue.
I had an '04 A3 3.2 and had the chain stretch/tensioner failure at around 4 years old. However when it went, it went suddenly and ran as if only firing on a couple of cylinders - really rough, not just a misfire but I suppose there are varying degrees of 'stretch'?
Fortunately mine was fixed (mostly) under warranty but it took the main dealer 3 attempts and around 3 months to sort it. That said once sorted I ran it for many years up to 90k with no further problems.
Fortunately mine was fixed (mostly) under warranty but it took the main dealer 3 attempts and around 3 months to sort it. That said once sorted I ran it for many years up to 90k with no further problems.
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