Hesitation/misfire help on ABY, please

[johne]

Help please folks…….

150 miles into a tank of petrol my ABY developed a misfire/roughness that makes it very difficult to drive. It’ll still boost and feels like you’ve lost a cylinder but I haven’t. The engine shakes badly at idle but disconnecting individual injectors doesn’t isolate any misfiring cylinder. With no load it’ll rev around 2000 rpm almost smoothly.

VagCom had:

00515 Idle position switch closed throttle F60. Intermittent short to ground
00525 Lambda sensor G36 no signal intermittent
00294 Pressure switch 1 for transmission state no signal intermittent
00517 Full throttle switch F81 no signal.

Cleared these and no faults reappeared during diagnostics other than noting the removal of injector leads.

Have replaced but made no improvement:

Both POS ignition amplifiers
NGK plugs with new
All 5 Beru coil packs, loom and boots (I’ve lots of those!)

Temperatures and oil pressure normal. Compression test gives 155 to 165psi across all cylinders. Does what you’d expect if you disconnect the ISV or MAF and returns on reconnection.

Standard ABY running Homefries

Final observation; there’s a noticeable smell of sulphur in the exhaust.

Suggestions please

John

[david1980]

wrong fuel/bad fuel?

[UrS4boy]

Search for my *VERY* recent post with a link to "One missing and Hesitation Diagnostic"

[johne]

Search for my *VERY* recent post with a link to "One missing and Hesitation Diagnostic"

Dave, in expectation of one of your "helpful" guides recommendations, I had already read it and what have I not already tried and listed in my post that it recommends and I've already tried?

I haven't replaced the fuel filter but it's not that old and I don't think it an be the issue with a car that drives and also has a problem at idle.

John

[johne]

wrong fuel/bad fuel?

Possible and on my list of increasingly desperate things to rule out by draining the tank and refilling. I didn't put diesel in by mistake or I wouldn't have got 150 miles without any problems.

Last fill up was nearly a full tank's worth of Tesco unleaded. Tesco's petrol may not be the best but it's at least fresh and unlikely to contain water. I checked on line to see if anyone had had problems with petrol from that site and there was nothing.

John

[Avantus]

Tps ok?

[UrS4boy]

Dave, in expectation of one of your "helpful" guides recommendations, I had already read it and what have I not already tried and listed in my post that it recommends and I've already tried?

Sorry for trying to post "helpful" links. I won't try to help you any more.

I think if you followed my diagnostic, particularly the POS /coil tests, you would have not spent needless money on POSs and coils that are obviously not the issue.

Good luck.

[Fat Audi 80]

It beats me, so I will just wish you the best of luck finding out what it is...

Cheers

Steve

[mike74]

Have you checked for any burst or disconnected hoses?

[simons2]

Have you checked your plug gaps and leads ?

[david1980]

Sorry for trying to post "helpful" links. I won't try to help you any more.

I think if you followed my diagnostic, particularly the POS /coil tests, you would have not spent needless money on POSs and coils that are obviously not the issue.

Good luck.

I think he means that he checked you're guide first as they are very helpful and so he could say he's gone through everything you've put in the guide rather than having to go away and check something.

[johne]

I think he means that he checked you're guide first as they are very helpful and so he could say he's gone through everything you've put in the guide rather than having to go away and check something.

Exactly - "divided by a common language"

POS units are very reasonable off eBay.com (US$25) and I think it's only responsible to keep spares of common failure items for our cars such as POS and coil packs especially when they're readily available new or off cars being broken for parts. My challenge here is that after running through the obvious things I've still got a car I can't drive and I'm relying on the collective knowledge of this helpful forum to suggest things I've missed and haven't tried so far.

It looks like it has to be replacing the fuel next.

John

[UrS4boy]

POS units are very reasonable off eBay.com (US$25)

I don't know *what* you purchased off eBay for $25 but I can tell you that a proper OE Bosch 4A0905351A is about US$190. Huco and Beru (slightly different designs) are still over US$110.

http://www.ecstuning.com/Search/SiteSearch/4A0905351A/

[johne]

I don't know *what* you purchased off eBay for $25 but I can tell you that a proper OE Bosch 4A0905351A is about US$190. Huco and Beru (slightly different designs) are still over US$110.

http://www.ecstuning.com/Search/SiteSearch/4A0905351A/

Search eBay.com using "4A0 905 351A" and you'll find a whole range of prices from $21 upwards. Don't forget that you can also use the Hitachi units from 6 cylinder engines as they have the same 3 POS per unit as that engine used the wasted spark principle with just 3 coils each firing 2 spark plugs.

John

[UrS4boy]

Detailed Power Output Stage (POS) info including using the spare channel

.. Don't forget that you can also use the Hitachi units from 6 cylinder engines as they have the same 3 POS per unit as that engine used the wasted spark principle with just 3 coils each firing 2 spark plugs.

Really.

http://forums.quattroworld.com/s4s6/msgs/15284.phtml

From this live label engine device map (click on the labels):

http://members.shaw.ca/speedtek/UrS%20Engine%20Bay%20Device%20Map.html