Missfire woes :-(

[andyr]

Wonder if anyone can help me out ?

I have a V40 2.0 Turbo

The car has developed an intermittant missfire.

I have had the OBD diags on the car and it comes up with no faults (generic OBD diags).

The car will idle fine and most of the time rev freely enough, but as soon as you drive the car, it misses like hell (unable to drive car it's that bad).

Naturally I thought it would be the HT side of things so I got new coils, plugs and leads, this has not fixed the problem.

One thing I did notice while out with the diags is that even with throttle fully open the diags was only registering 79.9%.
Even when you open the throttle body by hand to 100% the diags only read 78-79%, this may be our diags (as it's VAG-COM diags with a generic reader on).

It's beginning to do my head in now, I shall give the MAF sensor a clean and shall put a new fuel filter on it tomorrow.

Just wondered if any of you lot may have any ideas what this may be ?

Cheers

Andy

[Titch]

I have had the same issue with my T4 a few times now and every time bar one it was the plugs, at least thats what i thought.
Most recently it was still mis firing after i changed plugs, leads and coils but after going back to the drawing board i noticed that i had not completely tightened Spark Plug 2. I done this and it remedied the problem.

I am aware that this might not be your problem but surely worth a check as its a quick and cheap fix. Let me know how you get on.

[GATHY]

sounds very similar to my problem on my 2001 t4
i replaced plugs leads and it still did it.

turned out to be the head gasket going
do a compression test and check the water pressure when hot
or like me if you leave it to cool down over a few hours then release the coolant cap mine still had loads of pressure in the system which turned out to be forcing water into cy no;3

did eventually show up on the obd as misfire no.3 and emissons but it was a few weeks of head scratching for both me and volvo until the light give us a idea

[andyr]

Well, after a load of time and money, I have finally found the fault.

A very tired fuel pump.

Fine when has a full tank of fuel, but when gets beneath 1/3 tank, starts to 'miss' a little, the further the fuel goes down, the worse it gets !

Hope this may be of help to anyone else who may suffer these symptoms.

Cheers

Andy