S3 8P - Part Throttle Misfire at Midrange only?

S3 W · Oct 18, 2019

Hi all

Have been experiencing misfires under part throttle at midrange (3.5-4.5k) RPM. Curious to see if anyone else had the same issue & what they did to rectify it.

In brief, this only occurs at part throttle in the midrange, the car does not misfire at full throttle. You can hear the boost building & soon as it gets to the mid-range there are multiple misfires if you balance the throttle to be consistent between midrange only.

Car shows no CEL or any codes. Have changed for new all injectors, coil packs, spark plugs, cam follower, fuel filter, DV valve, cleaned the MAF & got inlet valves cleaned from carbon deposits within the last 500 miles & still the same symptom/misfire.

Appreciate any advice for anything I should look out for.

prt57 · Oct 19, 2019

As you have spent lots on this already, it is time to get it logged to see what is happening. RTech in Nuneaton should be able to sort this out for you rather than guessing.
Ignition problems should not get better at higher boost or revs so I’m thinking fuelling.
Has the fuel pump ever been off the little black rubber fuel pipe? Sometimes if it has been removed, little bits of rubber break off from inside and can cause a partial blockage to fuel going into the pump. However, again you would expect the problem to be there at higher revs too.

S3 W · Oct 19, 2019

prt57 said:
As you have spent lots on this already, it is time to get it logged to see what is happening. RTech in Nuneaton should be able to sort this out for you rather than guessing.
Ignition problems should not get better at higher boost or revs so I’m thinking fuelling.
Has the fuel pump ever been off the little black rubber fuel pipe? Sometimes if it has been removed, little bits of rubber break off from inside and can cause a partial blockage to fuel going into the pump. However, again you would expect the problem to be there at higher revs too.

Hi thanks for your comment, I also thought maybe fueling but this would be more of an issue on the full-throttle than partial throttle which isn't the case, was told maybe vacuum leak but the car boosts with no issues. Unfortunately, I'm not local to Rtech & don't know anyone in West London that truly knows what they're doing when logging data hence why id rather guess & pay the money towards parts than someone thinking they know what there looking at.

Managed to go out for a drive last night & noticed when the MAF is a connected issue can be replicated almost every time at midrange however when I disconnect the MAF, I can't seem to replicate the issue, going to put in a new MAF & will see if that makes any difference.

prt57 · Oct 19, 2019

S3 W said:
Hi thanks for your comment, I also thought maybe fueling but this would be more of an issue on the full-throttle than partial throttle which isn't the case, was told maybe vacuum leak but the car boosts with no issues. Unfortunately, I'm not local to Rtech & don't know anyone in West London that truly knows what they're doing when logging data hence why id rather guess & pay the money towards parts than someone thinking they know what there looking at.

Managed to go out for a drive last night & noticed when the MAF is a connected issue can be replicated almost every time at midrange however when I disconnect the MAF, I can't seem to replicate the issue, going to put in a new MAF & will see if that makes any difference.

I would ask the same questions on
TFSI tuning Facebook page before you spend any more cash.

K96 · Oct 19, 2019

I had a similar problem I was chasing for months and the misfiring started just like yours and worsened over time till it would misfire all over the rev range and was barely drive able.. I basically changed every part you could think of.

The cause was the fuel valve that screws into my manifold was cracked. Replaced this and the car has been running sweet since

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S3 8P - Part Throttle Misfire at Midrange only?

S3 W

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prt57

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S3 W

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prt57

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K96

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