Thanks Martin :-) info also here

Interstingly in those pictures the AFM is sitting where your's was - though it's not clear if that is a GT or Golf AFM and if it's at idle or not.

No idea on what should be standard airflow, so trying to get a few examples from people running GTs, find out what the average is and how that correlates to mine.

Andy, many thanks for the offer of spare AFM. I've got a spare here too but it's made no difference. Do you still run a GT as well or just the G40 turbo?

Is there anyone else in the West Midlands nr Cov, East Midlands nr Loughborough or Manchester that has a GT and a spare half hour we could use to check?

Edited 2 July, 200917 yr by cheys03

From that picture iirc my old GT used to sit where Martins does, although it was ages ago i think mine used to blip down to near where yours sits but never stayed there. I could be wrong but 80% sure yours is in the wrong position.

I have a spare one in Ilkeston, Derbyshire you can try. It should be standard as it has the blue sticker on the allen bolt and i think the black cover is sealed on.

Chris

You mentioned you were running AAU Cylinders

From the holy grail Haynes Manual

Compression Ratio

AAU - 9:8:1

AAV - 9:5:1

3F - 10:0:1

PY - 8:0:1

Don't know if anyone knows on here that the wrong pistons would cause the fueling problem

Cheers Martin. I think NZ is also 9:5:1. I'm using an AAV block. Wouldn't have thought this was the problem, but my knowledge is limted. Any comments anyone?

It won't be that I'm sure.

you say you have a hiss coming from the idle control screw. surely that would be where air is getting into the system. none of the 3 gts I've owned have made a hissing noise from the throttlebody. how far out has the idle control screw been turned? it should only be undone a couple of turns to give a good idle.

Yeah, the hiss comes from the throttle body where the idle screw takes in the air

Project96, I hope you don't mind...I nicked this pic from your polishing thread.

Put your finger over the hole and there's no problem.

I've adjusted the throttle butterflies to be completely shut when at idle so maybe the air pressure through the idle hole is now enough to make the whistling sound.

Edit: Yeah the idle screw is only out 2-3 turns

Edited 4 July, 200917 yr by cheys03

right, did fuel filter on mine today, and fixed a fuel leak after the filter. seems better now but still occasionally missing

also put standard exhaust back on, no idea if that made a difference

anyway on way home stopped at shop for some supplies and noticed rear of car smelt of fuel when i went to pop my rice crispies in the boot, nosey under and none of the pipework is leaking, but the pump itself was wet with petrol. weird i think. start the car up and the damn in line pump itself is seeping fuel ot from somewhere. the connections to the fuel lines on both ends are bone dry, but the pump itself is seeping fuel.

so going to source a new pump for it and see how we go

I had a pump do this. The steel hanger had rusted, expanding and eaten a whole in the pump exterior.

Temp fix was alloy sheet from a coke can wrapped around the pump exterior and held in place with 12hr set araldite (don't use the 15min crap). I say temporary but it lasted 5months! (and is still ok, but have since changed to an MPI pump).

Changing the filter has probably disturbed the pump and I reckon this has happened to your pump

YAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAYYY!!!

Played with the AFM again, undid the spring tension by about 1/3 a turn (alot!) to move it to approximately the same place at idle as Martin's.

The misfire is gone. At first it was overfueling to the point of kangarooing at 5,000rpm but after some adjustments it's much smoother and getting a very good mpg... Realise this is not a fix but a work-around. It's clear that somehow somewhere there is an air leak. I imagine that even with these adjustments to the AFM the fuel mapping will be changed and will probably under/overfueling all over the place...but at least it's not misfiring! Must get it on to a test rig to setup correctly.

Have no idea how to find the air leak though... have check everything at least three times!!

Oh yeah mines right churn the butter!!!!

good stuff mate, glad you sorted it!

i'm going to source a new/second hand pump with any luck but none of the kids on here are responding in the breaking cars section, you haven't got spare GT one kicking about for sale have you?

Thank you :-) Still have to find the blasted air leak though.

No sorry mate. I was about to buy one from vwmk3jon if that helps. Looked like a good pump, definately off a GT etc.

I would checking the throttle body gasket, inlet gasket. Jubliee clips on the air hose. Breathers. Has the throttle body been dewedged?

Thank you :-) Still have to find the blasted air leak though.

No sorry mate. I was about to buy one from vwmk3jon if that helps. Looked like a good pump, definately off a GT etc.

tried to pm him to no avail, really need this n all. pretty sure leak is getting worse. you didnt get a mobile number or similar for him did you?

cheers

Ben

I would checking the throttle body gasket, inlet gasket. Jubliee clips on the air hose. Breathers. Has the throttle body been dewedged?

when he brought it round mine he did the gasket and all the clips were tight. my throttlle been dewedged and doesn't hiss at all

I have a 1.3nz fuel pump it that helps

I would checking the throttle body gasket, inlet gasket. Jubliee clips on the air hose. Breathers. Has the throttle body been dewedged?

Throttle body gasket has been in standard form and then blue hylomared, as has the inlet manifold. Jubilee clips on air hose seem ok, breathers - no real difference with them removed and plugged both ends. Throttle body still has it's wedge virginity intact.

I think wherever the leak is coming from is before the throttle body as screwing the idle screw all the way in definately kills the engine.

I've changed the big hose from AFM to elbow and the elbow itself too. Well confused! Need a smoke machine methinks.

NZ fuel pump should be fine for a GT according to ETKA - the part number is the same.

Pic of observations:

Many thanks for your help so far guys.

Hey guys, unfortunately I'm still struggling with this problem. The tweaking with the AFM wasn't as successful as I'd hoped

Placing the dial where Martin's was at idle results in massive overfuel to the extent that the car won't easily start and really struggles maintaining an idle. (Martin I think this is why your's requires throttle to start).

I would really, genuinely very much appreciate it if anyone with a GT with the AFM lid loose (don't want you to take the lid off your's on my account) could have a look at the position of the dial as above at warm idle and post here the position and the approx speed of idle (with warm engine). This would really help decide if I have an air leak or some other cause my misfire.

Thank you all :-)

really, you need to get to a decent garage to set the AFM up mate. I heard they are laser aligned from the factory so its not something you can guess imo. You can do it using the voltage coming off the lambda iirc but i dont know how you do it.

Thanks Carver.

I'm fairly sure now it's not an air leak. I ran the car up to temp without the inlet elbow and stalled the engine by placing my hand over the throttle body (admittedly a silly move - very powerful vacuum!). The vacuum was maintained for well over a minute after the engine had stalled, and didn't appear to loose any pressure until I took my hand off. Did this a few times to confirm and also did the same over the large hose just after the AFM (with the oil breather T blocked). Same result, no loss of vacuum.

So maybe fuel delivery (though I can coat the plugs in soot by removing the blue temp sensor) or ECU/sensory.

Am on holiday next week so will just use the car as-is for now. After I'm back it will be put back to SPI to see if that eliminates any symptoms.

Well.... changed the back to standard AAV spi and cam. The 'misfire' is still there

So, what fun! I'm begining to think maybe the recent history is connected. In March I was a complete tool and managed to over-tighten and strip the  offside engine mount. Until it was replaced I ran with a inferior temporary solution for about a week. This did allow the exhaust to slap aginst then underside of the car under braking etc. A couple of weeks later the head gasket went.

Hmmmm... possibilities...

-> Maybe the exhaust system is damaged causing a partial blockage slighty increasing back pressure making it difficult for air/fuel to enter the cylinders giving the lean mixture shown on the plugs...?

-> Perhaps the valves are stickly (though the cylinders get good compression).

-> Lambda sensor damage during the headgasket failure (though this was swapped for 20mins on the drive - not driven, for a brand new Bosch unit)

-> Perhaps it's a fuel delivery problem (though both pumps and the filter have been changed and by removing the blue temp sender the plugs can be as sooty as a chimney).

Thinking the most likely is the exhaust... original CAT and middle box being abused by being bashed against the underside of the car when the mount went and then the headgasket going and steaming the whole thing...

What do you reckon chaps/chapesses? Any thoughts or suggestions? All gratefully received by an increasingly desperate man!!  

Can remember whether you've done this, but did you swap the dizzy and coil around with known-good units?

Can remember whether you've done this, but did you swap the dizzy and coil around with known-good units?

Yeah, in total there's been the original GT dizzy, two SPI dizzys and the GT dizzy with one of the SPI hall senders. The coil is new, though admitedly not tested in a other car the misfire remained exactly the same after it was fitted. I'm quite confident in the ignition system, most of it has been replaced or swapped to/from it's MPI/SPI version and did some thorough testing with a timing light to watch for misses.

Could be exhaust/catalyst related - but have you run it with the lambda unplugged from the wiring loom?

Does the catalyst end up glowing? Normally if a catalyst gets blocked (and/or exhaust blocked) then after a good thrashing the offending item will be significantly hotter than you'd expect - often glowing slightly!