a2 1.4tdi misfire

C

Chrissyboy92

Member
Hi,
I am a new member. I have a 1.4tdi 51 plate with 127000 miles on the clock. It has developed a major misfire which I am trying to diagnose. I have changed the fuel filter and no fault codes are showing up or warning lights. Been to local garage and they can't pinpoint the problem saying it could be a money pit trying to source, compression check, injector harness, carbon build up. Can anyone help? I am in fife Scotland if anyone is nearby.
 
Welcome. Sorry to read that your first post is a tale of woe, but I'm sure the forum can assist! Sounds like your local garage doesn't want your business!
You say no fault codes - what are you using to do a check scan?
Are there any other symptoms - is the misfire permanent, or does it go away after you re-start the car? Does the misfire only happen when the car is cold or warm? Has any other work been done to it around the time of the misfire starting?
 
dan_b said:
Welcome. Sorry to read that your first post is a tale of woe, but I'm sure the forum can assist! Sounds like your local garage doesn't want your business!
You say no fault codes - what are you using to do a check scan?
Are there any other symptoms - is the misfire permanent, or does it go away after you re-start the car? Does the misfire only happen when the car is cold or warm? Has any other work been done to it around the time of the misfire starting?
Click to expand...

Hi,
Thanks for the reply. Car has been scanned at the garage so sorry don't know which machine they used. The misfire has got gradually worse over the last week. It was happening after refuelling but now think this was a coincidence. Changed fuel filter. The misfire at worst throws out a lot of smoke on start up and runs very lumpy, driving it's down on power and very jumpy around town. Car has a full service history and I have only had the about 3 months. Looking for some inspiration so I can narrow down the cause.

Hopefully someone can help
 
Welcome.
Try changing injector wiring loom, as those wires take a lot of heat and can produce similar problem.
Have had such an issue and in my case turning off the climate would make it run smoother a bit, try turning it off and on on idle.
As for carbon buildup, I've seen my engine head removed at ~150k miles and it was nothing to be worried about.
Reason for the service was head gasket, water and oil mixing and this can be diagnosed by coolant expansion bottle going darker inside, check that as well.


Cheers
Neo
 
Hi,

Engine misfires will cause a DTC to be logged on the engine controller, so I'd suggest getting the car scanned by someone who has VCDS and can provide you with the output of the scan. Without the output you're starting from scratch.

As Neo advises, the injector wiring loom can fail. It's not an expensive part to purchase from a local dealer, but my advice would be to get the car scanned first to see what DTC's are thrown up.

Similar issues can be caused by a failed temperature sensor, but this is more likely to be the case if this issue occurs when the car is warm, not cold.
The sensor is of a dual configuration in one housing.
One half provides a signal to the engine ECU for correction of fuel/air mixture depending on engine temperature.
The other half provides a signal to the temperature gague.
If there is an issue in the half that provides the signal to the engine ECU, the engine may be at correct operating temperature according to the gauge but the ECU might be fueling it for a cold engine - hence black smoke.

There could also be an issue with the charge-cooler. A leak in the air from damaged pipework, or the intercooler itself, will cause mis-fueling.

Air filter - has it been changed?

When was the cambelt changed?

Are you capeable of removing the belt top cover and inspecting the wear of the belt?

Reason for asking the above - something you could try, if the car was running sweet prior to this issue, is a Italian tune-up.
Drive the car at a constant 4000RPM for 3 to 5 minutes once it is up to running temperature.

Fuel up with a full tank of high quality diesel such as Shell Nitro or BP Ultimate.

Hope this is of some use.

Cheers

Jeff
 
It's relatively straightforward - allow yourself 90-120mins to do it. The tricky part is working out what bits have to come out before you can access the rocker cover - e.g. take off the windscreen wiper, scuttle cover and air scoop...
 
Hooray looks like that did it. My little a2 is back to its best :) since owning I have replaced central locking ecu, fuel flap motor and the flexi part of the exhaust all in 3 months. Hopefully will be plain sailing now and can look at modding :)
 

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Hi, just a quick update. After a few weeks the misfire was back so took it along to Star Performance for a diagnostic check and finally got to the route of the problem. A faulty airflow meter. It now drive like a completely different car. Can't recommend star performance enough if u are near fife, Scotland will be booking in soon for a remap.
 
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