Intermittant missfire at idle

[Adam25]

hi guys

I have recently aquired an A4 Avant 2002 1.9tdi (awx engine) with some issues, the main one i have at the moment is as above, car starts fine cold and hot, when the car is warm however it starts fine but then starts missfiring, sometimes when you blip the throttle it kicks a small cloud of blueish grey smoke, but when it returns to idle its still missfires, sometimes if i leave it idling it will eventually even itself out. Driving wise it boosts as normal and on a normal run i get between 38-43mpg acceleration is fine and smooth. I have checked the injector smooth running on a snap-on eithos diagnostic machine and got these readings (whilst it was missfiring)

Cyl 1 -1.38mg/s
Cyl 2 -2.23mg/s
Cyl 3 2.99mg/s
Cyl 4 0.48mg/s

With the previous keeper being a friend of mine i know some of its history and that it recently had a brand new injector loom and crank sensor fitted along with a used second hand injector! Which one i dont know, and this cured the issue for a short time.

Any advice would be welcome as this car is my daily whilst i do an engine swap on my Nissan 200sx.

Adam

 

[QuattroCalum]

Have you checked to see if the camshaft is in good condition? http://www.myturbodiesel.com/wiki/camshaft-lobe-wear-inspection-and-replacement-on-tdi-pd-engine/

 

[Adam25]

I havent yet as i thought if the camshaft was worn it would missfire all the time?

 

[QuattroCalum]

Well you have a point there, diesels and missfires, the more complex they become, the more problems it creates.

 

[Adam25]

Your telling me lol, my suspicions are pointing at injectoron cylinder three but at the prices injectors are im just trying to make sure in my mind thats what it is.

 

[Gazwould]

Very rare for actual injector fault , common after 150k is injector loom , sub £60 .

 

[QuattroCalum]

Very rare for actual injector fault , common after 150k is injector loom , sub £60 .

Stated in the first post, new injector loom fitted

 

[Adam25]

@Gazwould injector loom was replaced only a couple of months ago. I think im just going to have to remove the rocker cover and have a look. Just wondered if going by the injector smooth running values would determine a faulty injector to be the cause?

 

[Adam25]

So I still have this issue clouding this otherwise lovely car, so far I have done the following...

Replaced the injector loom in the head with a brand new one from Audi
Replaced all 4 injectors with good reconditioned ones
Replaced the fuel filter
Replaced the cam belt and set the cam pulley using a friends VCDS

So now I'm in the position where the engine shakes quite violently at idle hot or cold, starts on the key and drives fine acceleration is good.

I have put a snap on diagnostic reader on it when it's at idle and the results are
Cyl 1. -3.05
Cyl 2 -2.57
Cyl 3. 2.99
Cyl 4. 2.99

If I gradually raise the revs and hold at 1500rpm cyl 3,4 and 1 return to around 0.40 and cyl 2 jumps up to 2.99

My friend who works in an Audi workshop reckons it's the dual mass flywheel stuck and at idle is imbalanced causing the shaking and the injector readings to be trying to compensate it. So I'm looking at replacing the clutch and flywheel possibly for a single mass flywheel?

If anyone has any suggestions please comment, I'm scratching my head with this.


Sent from my iPad using Tapatalk

 

[QuattroCalum]

So I still have this issue clouding this otherwise lovely car, so far I have done the following...

Replaced the injector loom in the head with a brand new one from Audi
Replaced all 4 injectors with good reconditioned ones
Replaced the fuel filter
Replaced the cam belt and set the cam pulley using a friends VCDS

So now I'm in the position where the engine shakes quite violently at idle hot or cold, starts on the key and drives fine acceleration is good.

I have put a snap on diagnostic reader on it when it's at idle and the results are
Cyl 1. -3.05
Cyl 2 -2.57
Cyl 3. 2.99
Cyl 4. 2.99

If I gradually raise the revs and hold at 1500rpm cyl 3,4 and 1 return to around 0.40 and cyl 2 jumps up to 2.99

My friend who works in an Audi workshop reckons it's the dual mass flywheel stuck and at idle is imbalanced causing the shaking and the injector readings to be trying to compensate it. So I'm looking at replacing the clutch and flywheel possibly for a single mass flywheel?

If anyone has any suggestions please comment, I'm scratching my head with this.


Sent from my iPad using Tapatalk

I wouldn't put a single mass flywheel on a diesel you will regret it if you do. Replace with a dual mass.


Sent from my iPhone using Tapatalk

 

[boffin486]

I just replaced My clutch & DMF a couple of weeks ago. The clutch was knacked (slipping) anyway but the symptoms of uneven idling (sounds just like a misfire) was being caused by the DMF. When I examined the old one, there was about 1/2 an inch of play in its springs!

 

[Adam25]

Problem has now been resolved, turns out two of the recon injectors i bought were faulty, replaced those with genuine bosch reconditioned ones and car runs perfect!

 

[QuattroCalum]

Problem has now been resolved, turns out two of the recon injectors i bought were faulty, replaced those with genuine bosch reconditioned ones and car runs perfect!

Glad you found the root of the problem, well done mate!