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Model specific boards => Golf mk2 => Topic started by: jonny-5 on 08 June 2012, 17:54
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Hi, i've had this problem for a few days now on my 9A converted mk2. It is that when I'm driving on part throttle occasionally the rev counter will drop to zero and the engine dies for a second and then bursts back into life often with a loud backfire out the exhaust!
It doesn't seem affected by operating temperature, car drives perfectly under load and wide open throttle, starts perfectly. I've tried a known good coil and distributor to no avail, have also recently changed the plugs, leads, dist cap, also changed almost all the short flexi vac hose joiners, cleaned the metering flap and throttle body.
Any idea where to go next? The thing is driving me mad!
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[broken record]
Check all of your earths around the engine bay
[/broken record]
If the rev counter's going to zero then the electrics are dying momentarily and then coming back in - you suddenly have no spark and fuel still going in and then spark and LOADS of fuel BANG!
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[broken record]
Check all of your earths around the engine bay
[/broken record]
If the rev counter's going to zero then the electrics are dying momentarily and then coming back in - you suddenly have no spark and fuel still going in and then spark and LOADS of fuel BANG!
Ditto... broken wire, loose earth, plug not on properly, maybe the loom is pulling on a plug when you give it gas, that sort of thing
Thom
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Been checking round today, cleaned all the earths I could find. The problem remains! It's definitely when you just come off throttle and then again when you put it back on. As I said it doesn't do it all the time but it's pretty much most of the time when driving with very little throttle and doing the above.
Cheers so far but any more help?
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Throttle switch?
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That was my thought too. Did the test as per the Haynes book and all appears to be in order. Don't see how that could interupt the spark system though
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Hall sender?
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Tried 2 different known good distributors so would rule that out. Swapped the king lead over today for another good one - no difference. Gunna try a new cap next
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Fuel pump can sometimes give that symptom check the lift pump?
Cold or warm when it does it?
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Swap out the earth from the head to the coil. Earth straps can sometimes fail, so I'd still be chasing that some more before following other routes of enquiry.
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rev counter droping to zero is the give away.
its electrical on the low tension side of things. dizzy caps and leads wont cure it
ether power / ground issue ecu tci h. loom or hall sender or bad connnections to the coil.
you swaped dizzys so shouldnt be , unliely to to be the coil as weack spark shows up under load. unlikely to be the tcih .
id be looking at all the connectors on the looms for sings of suboptimalness, general condiion of the loom often get wires fail where they go round the engine, oil + heat kills wires.
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Found the problem! Started testing the tci switch and then the efi controller all was well. Then I noticed the that some of the pins on the controller had signs of water corrosion, so I thought as I've cone this far I may as well open up the controller and check for damage. However no damage was found buuuutt the vac hose to the unit inside the controller was hanging lose and not doing anything! So can I pursume that it was not advancing the timing at all? I know it would have been rather sluggish but I haven't given it some beans in fear of something disasterous happening!
So I put it back on, connected everything and away I went. Only went for a short drive, it usually would have backfired ect about 5 time in the distance I went, but it drove lovely. I'm sure I couldn't have blown this pipe off when testing (blowing down tubes ect). A full test drive shall be conducted tomorrow morning.
Thanks for your input everyone
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More likely to be the moisture-damaged pins than the disconnected hose.
You've shoved everything around and re-connected things, so it's happy again.
Might be worth making sure everything's clean and dry so you don't get the problem coming back again.
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Yeh thought it was weird, don't see how that hose could have come off though - it's on pretty tight