2.5 TDI misfire/hesitation

[slarti]

Hopefully someone on here will be able to help me diagnose what's wrong with my car.

The car is a 1998 A4 2.5 V6 TDi quattro. I have recently noticed a misfire or hesitation when accelerating at around 2500-3250RPM with around half to three quarters thottle. When it comes in, it gives a judder through the car. To start with it was so slight that I thought it was just bumps in the road but now it's got much worse and I have to anticipate when it will happen and adjust how hard I'm accelerating and my pressure on the accelerator to minimise it.

Also, a while ago I notice that the speedo was reading 0 when I was coming to the end of a journey. Next time I drove it, it was fine. Since then it intermittanly drops to 0 or waves around on the dial. I have noticed that when it drops to 0 the fuel guage waves around a bit when going round corners or accelerating/braking.

I don't know if the two issues are related.

I ran a fault code scan with vag-com and the only one that came up was this:

Address 01: Engine
Controller: 8D0 907 401 B
Component: 2.5l/4VT EDC G00SG D41
Coding: 02003
Shop #: WSC 06335
1 Fault Found:
00625 - Vehicle Speed Signal
27-10 - Implausible Signal - Intermittent
Readiness: N/A

It sounds like this might explain the speedo problem but I can't find any references to what this fault might actually be.

Sorry for the long post. Any suggestions or ideas welcome.

[shaun tdi]

Hi there.. As regards to your misfire i have the same problem and have just found out that my no 1 injector is clogged so im going to try some injector cleaner first.
Hope this helps as it might be worth checking your injectors.

[VAGMAN54]

the speedo sensor does cause problems with the fuel gauge ,it a common fault it worth changing this first to see if it is responsible for your misfire fault,the ecu needs to see a speed signal as well as the instrument panel......

[slarti]

Thanks for the suggestions.

Any idea where the speedo sensor is? I can't find any reference to it anywhere. What would it be called in the parts catalogue?

[VAGMAN54]

vehicle speed sensor is on the gearbox,whats your engine and gearbox code,is it an auto box or manual ?

[slarti]

I'm not sure of the codes, I can find out this weekend.

The engine is the 2.5 V6 TDi (I think its the 150bhp version) and the transmission is 6-speed manual quattro.