Audi 80 Avant - Intermittant misfire ?

**kbowern** · 09-12-2006,03:45 PM

I have an Audi 80 Avant with a ABK engine, which I call full fuel injection,
with an intermittant misfire.

Well it feels like a misfire. Very lumpy at low revs and lack of power,
but it still goes.

Over the course of time it's had a new coil,
distributor ( iffy hall effect sender ), new plugs, distributor cap, leads.

Problems goes away and comes back after various lengths of time.

I can find no pattern.

Just tried cleaning, Air Flow Meter sensor, not easy as it's in a plastic housing. Unsure if this has changed anything.

It passes it's emissions test at the MOT so don't think it's the Lamda sensor,
unless it's an intermittant fault on that.

Very tricky one.

**brd** · 11-12-2006,03:52 PM

I have the same problem.... and was about to update my recent posts for when I asked for help... as I though it had gone, but unfortunately not.

I am checking another possibility at the moment which may be a cause. The vent on the petrol tank (which could be through the cap?) could be blocked... there was always a pssshhhttt when taking it off. I put the cap on after the last refill of the tank only half way (under the cover so shouldn't fall out - I hope! - but will get some cheap one that doesn't seal for the test)... and so far no problems with running. I need to drive more to see though as I thought I had it sorted before.
I do know that in changing the air filter, plugs, leads, dristributor cap (and soon the fuel filter) that it runs much better... but the stuttering was still there.... generally when hot and in traffic... but also on the motorway too.
I'ts been bugging me big time now for a while... so am trying my damnest to fix it as I use the car quite a bit. If you find something, do post, as I could realy do with ideas (if the fuel cap thing doesn't work)!

**kbowern** · 15-12-2006,06:11 PM

That is another idea, something else to bear in mind.

At one point in time I did think that if I run the petrol tank low
I'd get the misfire problem. I was thinking I could be drawing muck
in from the bottom of the petrol tank. But it could be
a blocked breather pipe, as you say. I'll investigate.

**brd** · 15-12-2006,07:33 PM

Damn... has happened again... the intermittant stuttering. Weather has warmed up a bit, and immediately its not running good again. I just got the fuel filter, so I'll check the flow rate from the tank aswell when changing it. I do go from full to empty to full all the time, so if there is rubbish in the tank, I may get close to it... but would expect the fuel filter to sort that out.

I'm going to check the water temperature sensor on the radiator aswell. I found a french manual that covers the ABK engine, so i have readings to check against now. Will keep you posted.

**adamss24** · 15-12-2006,07:47 PM

Get a cheap OBD2 lead of ebay and an old type 2+2 adaptor for older audis and download the shareware version of vag-com on an old laptop and you should be able to see if there are any trouble codes in the memory !

**brd** · 15-12-2006,07:55 PM

I like your thinking ... and have been considering that alright.... just not so sure which to get, nor where exactly it plugs in. You know?

At least maybe then I can test for errors when it's happening.... as its intermittant. I have already got two Audi garages to check it out, but they say nothing comes up on the diagnosis systems.

**adamss24** · 15-12-2006,08:10 PM

The two conectors are inside the box on the driver side in the plenum/bulkhead and they are black(brown on some moddels !) and white in colour. Look for obd2 2+2 on ebay and you will see witch is it. They different in shape and wont go in the wrong plug. Check if there are 4 cables going to the conectors because if they only 3 the diagnostic wont work ! I had tried myself with great success on a l reg audi 80 2.0L petrol so i think yours will work just fine !

**kbowern** · 07-01-2007,03:14 PM

since cleaning MAF ( air flow sensor ) car seems to be running OK, but
I haven't done a lot of miles recently so not really convinced

**brd** · 08-01-2007,10:43 AM

I'll check that out... how did you clean it?
The car has been back in with Audi again... they still can't find anything wrong. Thankfully though I drove it to them with the problem actually happening and one of their guys took the car out and confirmed that there is a problem. Only, then he booked it in for the following week and it was running fine then... phew... ! Weather is colder now, and seems like prob happens less when colder.
Am running out of ideas now.... !

**kbowern** · 08-01-2007,12:25 PM

I cleaned the air flow sensor with a solvent cleaner and a cotton wool bud.

If i did it again i would use "Ambersands" which is a de-greaser and just spray if on. I guess you need to be careful with what you use.