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cheys03

GTish problem. Lots of test done but no answer...

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cheys03

The fuel pressure regulator has been swapped for another with no change in symptoms. I also setup the proper GT vacuum system inc. warm air feed etc. incase too much vacuum was effecting the fuel pressure regulator. Again no change. Also run some injector cleaner and BP 97 Ultimate fuel, no difference.

Hall sensor was swapped for the late SPI one (looks the same as the Mk4 ones) which didn't help :-( Instrument rev counter also gives good steady info.

Currenty rolling around my head is the throttle potentiometer making the ECU think the throttle is more closed than it actually is or something else sensory...

I wish I had access to a full garage of diagnostic equipment!

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Coops 1.3

mine turned out to be the coolant temp sensor i think, car was fine until warm then stutters and cuts out. so i simply unplugged the sensor and bridged the plug with a bit of copper wire when engine was still hot and continued on my journey home from work, car was fine all the way back. so hopefully new sensor should sort it fully. sorry if this isnt much help fella but thought i'd share my experiences

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cheys03

All information is good information. Cheers dude :-)

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Coops 1.3

dammit, i was wrong. put new sensor on last night and was fine until this evening as i went for a spin after changing rear wheel bearings. still doing the judder and power loss uphill, engine under load. fuel filter and injector cleaner next

bugger it

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residentmelon

I saw you said it could be the fuel pumps did you change them for GT one's as I read the GT fuel pump have to run at a higher bar.

I brought a Loon GT witch was running crap under 2000 revs and hunting put you foot down and it was fine

Found out it was the fuel pump at the back under the car was wrong and the one in the tank was rusting and the ecu water change both and running new ecu and ran better.

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cheys03

Coops, Resident Melon - thanks for the info :-)

I've tried to tweak a spare AFM - basically reducing the air flap tension and screwing the bypass screw all the way in. In theory this should make the engine run rich. It didn't. So I unplugged the lambda to prevent the ECU from correcting the rich condition - did appear to make a difference. (however I have tried a brand new bosch lambda replacement without any change, so think the lambda itself is ok). When unplugged the engine is supposed to run rich, but after 36miles the plugs still show lean :-/

I think the ECU is suffering from Catch 22 - lean running makes the engine misfire which dumps unburnt fuel into the exhaust. The lambda reads this fuel as a rich mixture and then attempts to lean out the mixture by shortening the injector open time. This in turn leads to a lean condition etc...etc...

Residentmelon, your symptoms interest me :-) I have changed the ECU and the in-line fuel pump is from a G40 @ ~ 87,000miles and so should be ok (I should really check the model number to confirm this though). However the in-tank pump is still the same one from the factory and last time I looked the mesh was on it's last legs. I'll pick up a new one from GSF today and see how it goes, probably change the filter at the same time (though it was last changed in Feb). Cheers!

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residentmelon

Reading whats your car doing sounds just like my car when I brought it ever few seconds on sounded on the verge of stalling

I brought a in tank fuel pump off here for £5 so check on here first and a ECU for £30

what about the acumlator next to the fuel pump could that be blocked.

Also I phone my brother the mechanic who fixed it with me and he said the return fuel line was block and twisted which was letting fuel return to the tank which may have been causing it to run crap.

is the car in manchester or coventry?

Edited by residentmelon

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Coops 1.3

full tank in the car now and injector cleaner additive in there. off to leeds this evening from derby.................see how it goes

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cheys03

Put in the new in tank pump - bleedin hell it made some noise! I fitted two other new in-tank pumps in Jan and they made a crap load of noise too. Surely I'm either fitting them wrong or something... but then why would the original pump be nice and quiet? Do they need to wear in?

Anyway. then fitted the new fuel filter.

No change :-(

Replaced old in-tank pump as at least it's quiet!

The full VAG part number on the in-line pump is worn away, just at the end where if the is a 'B' it for AAV/AAU and not 'B' is for NZ/GT/G40. I couldn't see any remains of the character though, and do trust the seller.

Accumulator is a possibility.

I should really get the fuel pressure at the rail measured by a garage I guess...

Car is in either Coventry. Loughborough or Manchester depending on which weekend it is :-)

Fingers crossed for you Coops

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residentmelon

My GT is in solihull and if you wanna drop by too try the ECU or fuel pump your welcome

Edited by residentmelon

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Guest mk1poloblade

Coil

Cambelt 1 tooth out??

Knackered valve?

Exhaust issues (too small a bore?)

will be one of these...

if you have adjusted the cambelt and no change.. disconect the exhaust from before the cat section should be...

if still the same you may need to strip the head down and re build!

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cheys03

residentmelon - awesome offer! Nice one :-) will send PM.

Coil

Has now been replaced - no change

Cambelt 1 tooth out??

Advanced it 1 tooth, no change. Measured TDC and full close of valves - at most it is 1/2 tooth out. So without a vernier will always be a compromise.

Knackered valve?

Hmm, still possible but why would the spark plugs show lean mixture...

Exhaust issues (too small a bore?)

Would this cause this typre of misfire at low load and lean mixture?

Cheers

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cheys03

oooh, a couple of other tets I tried today:

Unhooked battery negative with car runnining - engine continued to run until I used main beams - at which point the engine just didn't have enough juice and died. Should this be the case?

Alternator is 55A and appears to give good voltage. Have a 65A unit from a GT too which could be fitted in it's place...

Bridged the blue temp sendor with a paperclip after seeing Coops's troubleshooting above. Made no change.

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cheys03

Removed the lambda from the exhaust today to see if excess back pressure was causing the misfire.

Idle seemed better but hard to tell over the volume. 2,000rpm was exactly the same though.

Sounded luuuuuuuurvely :-)

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cheys03

Inline fuel pump gets 13.12v at idle.

No difference with throttle poteniometer unplugged.

Thought I had it cracked earlier - if I listen to the engine near the throttle body I can hear a hissing - so thought air is making it's way past a seal or gasket. When you turn the engine off the hissing can still be heard until ~1.5seconds afterwards, when it dies out (like taking a kettle off the heat).

The noise doesn't seems to be related to throttle opening, though after ~1,500rpm the engine noise drowns the hiss so it's difficult to tell.

Sprayed WD40 over the throttle body without any change to the noise. Thought it may be the throttle body manifold so took it off. Found what looked like to be WD40 inside the throttlebody. Cleaned off all surfaces and the gasket, replaced with blue hylomar gasket sealant and rebuilt. Fired up, noise still there. :-(

Anyone with a GT, can you hear a low hissing noise from near the throttle body at idle? Much appreciate any info. Cheers!

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Coops 1.3

think most cars make that hiss mate, unlilkely to be anything to do with the issue. my clio does it and as you say most noticeable when cars turned off as its contiunues for a second or so and dies away

i have now zip tied on the connector on my blue coolant temp sensor sender in the engine bay. touch wood its not 'kangarood' since. i am also still running a full tank with injector cleaner through the car, but only clocked 70 miles so far, plenty to go.

will change fuel filter after this tank and refil to full and use other half of injector cleaner also

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cheys03

Well, first of all let me thank ResidentMelon (Martin) for all his help and generous lending of parts in true troubleshooting form! Martin you're a gent! Many thanks!

So, first we swapped the in-line fuel pump. No change.

Then we swapped the ECU for an 'N' GT one. No change.

Then we set about figuring out the whistling noise coming from the throttlebody (a noise which wasn't coming from Martin's throttlebody). After much scratching of heads it was found to be air rushing in to the idle screw bypass hole thing inside the large butterfly bit. No worries there then which is good.

What we came back to the AFM where a difference was found..!

My AFM barely gets going at idle where as Martin's makes it a way around the track. Both are set to stock spring tension and the same turns on the bypass screw. Unfortunately it didn't occur at the time to swap the AFMs to further confirm.

My thought is that if Martin's AFM is correct and given that I have tried a spare AFM, then my AFM isn't receiving the right airflow for the engine speed meaning air must be getting into the intake after the AFM. The ECU would be receiving a low airflow reading from the AFM and would therefore underfuel....or something :-)

This all rests on Martin's being correct. So, for a second opinion - does anyone with a GT know or have the ability to check the position of their AFM arm at idle?

Pic of observations:

Img_2862-1.jpg

Idle = 950rpm on my car and unknown but similar on Martin's. Note I have to run to about 2,500rpm to get my AFM to the same position as Martin's, so don't think differing idle speeds is the reason.

All help much appreciated chaps/chapesses :-)

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residentmelon

No worries hope you find the solution soon

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Coops 1.3

how do you get that pic? take the top cover off the afm? i'd like to check mine

cant believe it never occured to swap his onto yours?

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residentmelon

it was sunny lol!!

Edited by residentmelon

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cheys03

Yeah just pop the top cover off. It's held on with silicone so not too hard.

cant believe it never occured to swap his onto yours?

I blame the petrol fumes :roll:

Edited by cheys03

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residentmelon

Well i did have a sip, the pint of petrol looked so tempting

Edited by residentmelon

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Andy

Think I've got at least one spare GT AFM in Leamington that you'd be welcome to try. Will have a look in the garage tomorrow.

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residentmelon

where is it written what should be the standard air flow

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