Oh no! Massive misfire!

[newsh]

Thought I'd take the coupe out tfor a quick run today as I won't be driving it for a few days. Seemed to be going well then all of a sudden when I floored it at about 2k5 it missed then every time I use more than about 1/4 throttle it misses really badly, like overboost cutout but more lumpy and at quite low boost levels had a quick look for hoses blown off but can't see anything obvious.. MAF connector off-on didn't sort it.. Sometimes these cars can really do your head in

[Ross]

Are you running coil packs on it now or still old-skool 3B dizziness?

sounds like my avant when i had a split spark plug boot...

[denniselbows]

Do you still run with a dizzy if so check the rotor arm I had the end burn off on mine once . It would run fine until the boost started to come in and end up in massive miss fire. God knows how it didn't blow the engine as there was about a10mm gap

[andy10v]

Did you try driving it with the maf unplugged?

[newsh]

I'm still on a dizzy. No stray sparks visible in the dark.. Will have a look in the morning.
With MAF unplugged it drives but will not pull any throttle at all. With MAF plugged in it misfires very badly at anything over 1Bar of boost. Just before this it was struggling to idle, I thought the ISV was stuck so wiggled the plug and it seemed to sort out.

[Nero]

I had that problem recently with an AAN S6. Changed everything, hoses, WGFV, coils etc. Turned out to be the throttle position sensor on the throttle body. Never thought of that, but it was broken. Might be worth a try.

[newsh]

So its cured itself.
I went and pulled the codes, had Lambda intermittent (plus MAF and ISV which I'd unplugged while it was running, engine speed (not running) and Carbon can valve (not present) . Pulled the fuses to reset the ecu, went for a drive, goes like a train. Seems I may have an intermittant lambda fault though..

Plus the avant cured itself too of it's dodgy rear CVJ... Must have been a stone in the caliper

All in all its been a great day for cars fixing themselves.

[LHD_Kid]

So its cured itself.
I went and pulled the codes, had Lambda intermittent (plus MAF and ISV which I'd unplugged while it was running, engine speed (not running) and Carbon can valve (not present) . Pulled the fuses to reset the ecu, went for a drive, goes like a train. Seems I may have an intermittant lambda fault though..

Plus the avant cured itself too of it's dodgy rear CVJ... Must have been a stone in the caliper

All in all its been a great day for cars fixing themselves.

Did anything get wet? I mean, I don't think you said it was a rainy night...?

Mine has been known to misfire when driving through huge amounts of standing water - like jet washing the engine... The dizzy area sure doesn't like to get wet...

The lambda fault woulkd not cause huge misfires though,surely ?

Chris

[newsh]

Hi Chris, it does'nt seem to be related to damp and I've checked plugs and leads. Cap and rotor have not had a lot of use.

Anyway the missfire came back again today along with the lambda code, cleaned the lambda connections at the firewall plugs which certainly looked a bit corroded, this seems to have cured the misfire, Lambda fault (I think it said "Adaptation limit not reached, intermittent") has not come back and car was driving well but then..

After flooring it a couple of times I realised it was only making mechanical boost (this is about 1.3Bar on my car) WGFV was clicking when throttle blipped so pulled the connector off the MFTS and took it for a drive and full boost was back. Again the connection looked dirty so I cleaned with Caig De-Oxit which seemed to sort it out for a while, then it went again.. Luckily I have a spare MFTS I got off Terry Bullwon ..

[andy10v]

If the mfts is corroded the plug might be as well, you can get a new plug, and pins with wires for about £5 from audi, though you need to join it to the loom.

[newsh]

Andy, I'm thinking that too, the plug looks pretty bad but I think I'll need to take the rad out to really get a good look at it, unless I can ease the loom up enough.. Are they 1/4" spade type connectors? We have them at work and a proper AMP crimping machine.

[UrS4boy]

MFTS info

Here is a link to some MFTS info, including info about the 4 pin plug (which will likely crumble in your hand if you are attempting to remove the pins):

http://forums.quattroworld.com/s4s6/msgs/22584.phtml

[andy10v]

Andy, I'm thinking that too, the plug looks pretty bad but I think I'll need to take the rad out to really get a good look at it, unless I can ease the loom up enough.. Are they 1/4" spade type connectors? We have them at work and a proper AMP crimping machine.

If the plug looks bad, the inside is normally rotten.

The mfts loom does not come up very high as it goes into another loom (unless you slit the covering sleeve for the next bit of loom), it can be done it the car but is a doddle with the rad out, you will be bleeding the system anyway.

I don't know what they connections are are I am afraid, I bought the plug, its a couple of pound, then you buy the about 12" of wire with a pin on each end (so need 2 to give 4 pins), they slip into the plug and clip into place, then you cut off the original mfts and join the new lot on.

I gues you might be able to de pin the old plug, clean the contacts and fit a new plug but the parts are so cheap as long as you don't mind sorting the wiring it makes sense to go new.