missfire with a4 1.9tdi... driving me nuts

[lancasterchelse]

The story so far…. It is driving me nuts

I have an audi A4 tdi AFN engine… 1.9…. 150,000 miles

About 18 months ago I started to have a severe miss-fire
Some days it would be very bad and on one occasion it went into limp mode
Eventually I had the following work done…

4 new/recon injectors, new temp sensor and terminals
I have also blocked off the exhaust gas pipe from recirculating back into the manifold

The misfire is not as bad but happens most days. I couldn’t sell it as it is.

Theories include….. corroded terminals inside the EMU box….. it looks fine but has got wet at some point….. something to do with the air intake ??

The original fault codes (about a year ago) were…. Injection start control control difference/ needle lift sensor G80/incorrect signal… 00550 p0017 00542 p0155

Any help anyone

[lancasterchelse]

its a 1998 car

another theory is a fault on the electric harness that connects the injectors ???
there was a recall tears ago ????

[Col]

Problems like this are a nightmare.

You could end up spending a fortune getting it diagnosed with no results.

Have you considered setting yourself up with vagcom which would allow you to self diagnose? Look in the vagcom subforum for information.

My guesses would be;

Another faulty needle lift sensor (which by the way is integral with injector Nr.3). I'd guess that on the recon injectors you've had fitted they would have cleaned / re-profiled the pintle and nozzel but left the lift sensor bit alone as I'd guess it isn't a servicable part of the injector.

or

Pump timing; this you can check and adjust dynamically wirh vagcom.


There are some Pro mechanics on here and hopefully they'll read this and shed some more light.

[lancasterchelse]

thanks very much for your reply BigCol
I will look into your ideas and suggestions
as you say..... I've already spent about £700 and the car is probably only worth £2k at most !!!!

[Col]

Getting vagcom is the way forward then !

[paul b]

Could be the throttle body. Costly though. If you're lucky you could strip it down and replace the internal parts much cheaper.
Paul

[Col]

Could be the throttle body. Costly though. If you're lucky you could strip it down and replace the internal parts much cheaper.
Paul

Didn't think there was a throttle body on the AFN ?

[paul b]

You could be right BigCol, I have not worked on one with AFN engine, but I have with others with one.
Paul

[onzarob]

Didn't think there was a throttle body on the AFN ?

Your right Col, No throttle body on a diesel thats on petrol engines!!!

A Miss-fire is probably the wrong description for a diesel engine as it compression ignition. how would you describe the symptoms, vibration, noisy running lumpy running etc. Misfire is more of a petrol engine symptom

[ruud boy]

A quick check for the needle lift sender (as bigcol says is the No.3 injector) is to pick the revs up to around 4000rpm and with a SMALL hammer tap the injector if it misses hard you know this is the fault.