'93 S4 Missfire???

[merlin's S4]

Hi guys! Anyone got any ideas as to the cause of the missfire on my '93 S4? It's been happening for a while now but seems to be completely random and it's really starting to bug me! It's only a small miss (not like the big electrical missfire under load that I had when a coil pack was faulty) but it can happen at any time, whether you're accelerating hard or soft or whether you're just cruising at any speed. I sometimes think that it's more frequent when it's cold but I'm not entirely sure. Like I said it seems completely random and the car drives and pulls fine the rest of the time which is why it's so hard to trace.

Any Ideas???

[S2 Ant]

Have you checked the condition of the plugs?

[shadquattro]

may be worthwhile getting the injectors tested

[merlin's S4]

No I've not had the injectors checked. The spark plugs have only done about 5k, I replaced them with the genuine Bosch items not long ago. I've cleaned the MAF Sensor and checked the POS (Ignition amplifiers). I've also managed to blink out the diagnostic code 2111 (Engine speed sensor) but I know that this code sometimes shows itself anyway but the engine was running when I did the check! I've taken the sensor out and cleaned it but that still doesn't seem to have solved the problem!

[s4_rider]

Did you replace the fuelfilter already ?

[merlin's S4]

Well my new fuel filter and engine speed sensor have been ordered from the trusty guys at Vagparts so fingers crossed that this will do the trick!

[gavs20v]

coolio, out of interest how much was the speed sensor compared to the price i told you on audifans from audi?
Gav

[Henka]

Check fault codes. My S2 under hard load sometimes started to sputter. And it was random. Fuel pump was toast.

[merlin's S4]

coolio, out of interest how much was the speed sensor compared to the price i told you on audifans from audi?
Gav

Speed sensor was £40.56 and fuel filter was 8.49. I think this was inc VAT. Not much different to the Audi price but I don't like to buy from the dealer out of principal. Seems whenever I'm desperate for something they stitch me up! Anyway hope this does the trick for the time being. Cambelt and Head Gasket need doing soon and I think this may hurt the wallet somewhat!!!

[merlin's S4]

Well fitted the new engine speed sensor and fuel filter yesterday and took the beast for a spin but the missfire was still there! Suddenly had a brain wave and disconnected the ecu to erase the fault code and HOORAY it seemed to work, drove around for a bit in the afternoon and everything was fine. Checked for fault codes when I got home and nothing showed up Job done or was it?
Took the car out this morning in the cold and guess what, yep it missfired twice and the fault code's now showing again (2111-engine speed sensor).
This has really annoyed me, £50 down the pan and still no answer!

Any more ideas???

[S2central.net]

Did you get that fault code with the engine OFF or running ?

Is the misfire at part throttle, full throttle or both ?

Tried to borrow a different MAF yet ?

Always clear fault codes when changing components as the ECU stores them forever...


Paul

[merlin's S4]

The missfire seems completely random, it can be at full throttle or sometimes with hardly any throttle ie. just cruising at any speed it'll miss maybe once. Obviously it's harsher and more obvious when you're accelerating. I'm starting to think that the problem maybe worse when it's cold but the missfire doesn't seem to be limited to this or to a particular engine speed or throttle position.

The engine is running when I do the diognostic check as I'm only bridgeing the two diagnostic terminals to blink out the code on the dash! I have deleted the code but it comes back.

Tried a spare MAF as well as the two POS (ignition amplifiers) but neither made a difference! Although there's no guarantee that both the MAFs aren't crap, although I have cleaned them both.

[Knight Rider S4]

HI i have 93 S4 and i had same sort of problem at the end of last year were the car was spluttery intermentally and had to take to Audi and they sorted problem by fitting a new power end stage to car (little black module i think on bulk head)