starting troubles on a gt engine

[deathhour]

my 3f gt engine starts but stops immediately, changed the dizzy cleaned the fuel injectors and throttle body

does any1 have any suggestions on why it doesn't start

when I turn the ignition the engine starts but its very rough and shacks alot and when I press the accelator pedal the engine cuts out

[deathhour]

oh yeah and when it was running the short time after its conversion from a 1 litre there was smoke comming out of the exhust manfold where the hot air feed is suppose to go.

[pettsy]

smoke comming out of the exhust manfold where the hot air feed is suppose to go.

possibly some oil spilt on the exhust manifold..and the heat is just burning it off

[Tahrey1043]

you have a tacho on it? if so whats the revs like when it's shaking?

maybe one or more of the pistons isn't firing properly...

do you snap the throttle open, or does it die even if you do it slowly and gently?

possibly a lambda/fuelling issue?

[deathhour]

yeah it even dies when I gently open the throttle. Don't have a tacho meter so don't know what the rev's are.

But could put in my different clocks to have a look. Might need to change the inline fuel pump to the gt one, but I've read in some of these previous forums that a normal inline fuel pump would work also. And the engine has previous ran once for about 15mins, but idling was a bit rough because I used a AUU distributor which is different from a gt one

[Tahrey1043]

i'd be surprised if the inline pump was giving you troubles - at least, when i refer to haynes, all the fuel pumps on all the polos have the same specs. It's only when you get up the top end nearer to the engine (notably on the G) that there's a slight difference in supply rate. Shouldn't really matter at idle anyway, only when you're caning it hard in the top third of the rev range...

You have put all the correct GT bits on and wired it up properly, yes? Far as i've heard converting from SPi to MPi is a total pain in the ass on the electronics side.

right now i'd go with a misfiring theory as lumpy, probably slow idle that doesnt respond to the throttle suggests somethings up. possibly a combination of missing on a cylinder & a half ( sounds funny, but mine did that) and the throttle potentiometer not working? So when you open the butterfly even a crack the tiny idling squits from the injectors no longer make a rich enough mixture to keep it running? (with it stalling before there's a chance for the fumes to hit the lambda..)

or even a knackered hall sender / ignition pack messing up the timing / strength of the sparks.
(hehe... have you... ahem... checked the HT leads?)

mysterious!

[deathhour]

it isn't the distributor or the ignition coil because I've just replaced both of them, are the any areas where there can be a vacum leak? aspect for the throttle body?

haven't changed the spark splugs yet could those lead to stalling problems?

but I'm sure there's a vacum leak somewhere in the inlet manafold, any suggestions where that can be?

[Tahrey1043]

i dont know anything about the vacuum system personally so cant help there, sorry

have you checked each plug to make sure it's getting current and producing a good spark?

[deathhour]

yeah I might get new spark plugs but I don't think the problem is there. everytime i open the butterfly i think the sparks misfire and backfire, might be a fuel rail problem

[deathhour]

In the hayes manuel it says when you take out the potentiometer and put it back in afterwards you have to match it with the ECU with "dedicated electronice test equipment, refer to a vw dealer for advice"

what does that mean ? does it just need to be tested that its working or do vw dealers do something technical with their specialist equipment???

Would the potentiometer affect idelling? shall I give it a good clean with wd40?

[Tahrey1043]

havent a clue mate but its probably overzealous ... ???

dealers might not even have the stuff to test it with any more (its a more than 10 years old car now after all) and enough people here have done engine, ECU, and bits-of-engines swaps that would include either throttle bits or mis-matched throttle/ECU without having to do that. have you even touched it?

i really cant see how the sparkers misfiring / backfiring can be a fuel rail problem... its not a diesel... unless you've got it really hot somehow, there wont be any kind of preignition occuring at a just-started idle without a spark, no matter when the fuel's put in.

maybe your hall sensors shot or something? or a screwy ECU... (although the maps should be hardcoded in the replacable ROM, it's runtime programs might be on the blink.... try disconnecting the battery for a few hours and seeing if its any better after?)

its really wierd that any touch of the throttle sends it off though. have you tried disconnecting the potentiometer, anything like that, and seeing what happens when you brush the pedal?

And surely, someone else must have a clue on this????????

[amstrange1]

The symptoms you describe are classic ones of an impending hall sender failure, or coil failure. Are you sure the coil and dizzy you're using are healthy? If you've still got an AAU dizzy handy it'll work, but not very well - but would be enough to eliminate problems with your GT dizzy. The coils are prone to failure too, I usually keep a couple of working spares in my shed for such an occasion.

You have got the plug leads on in the right order? And the leads, dizzy cap and rotor arm are all okay? Can you hear both fuel pumps prime when you turn on the ignition? Is the ignition timing set correctly?

I'd look at the above before you start trying to persue sender issues.

[deathhour]

well finally fixed the starting idelling problems, it was a mixture of not screwing the negative cable on the battery and the afm sensor, had to find a sensor a bought on ebay and put it between the 1 and 4 metal strips on the plug, but might try putting it on 3 and 4 because the warning light is on, on the dash board. I put it on 2 and 4 and the engine wouldn't start lol

any everything seems fine at the moment and I hope it stays like that for a while.

I've put a normal AUU gearbox on my gt engine, the performance is way down from when I had a gt gearbox on it, does the gt gearbox really improves the performance of a gt engine?? Or do I need to tune up the engine, before the performance returns?

[GroovyCarrot]

The GT box is close ratio, which lets you hold the engine in the peak power band across gear changes at the expense of top speed. The AAU gearbox is an economy five speed box and so has much longer ratios, so larger differences between gears, so it's harder to keep it on peak power so accelleration will be slower but cruising will be more comfortable as the taller gearing allows lower revs at higher speeds.

[Tahrey1043]

thought the AAU box is what you had, groovy? the really tight ratio thing, more so than the GT, to squeeze every last bit of 45bhp oomph from the little motor

er, then again... i might be misreading the last bit of an AAV as a U which would be the 8P one right? GT wouldnt be too happy with that... it'll go alright if you give it a lot of revs, but you'll have to do that every time if you want the full performance.

mind you it wont leave you in a power flatspot pickle too often, for a high revving engine (comparitively, it's no VTEC after all) the GT doesnt lose as much of the bottom end as you might expect. I'd think your economy figures would probably be quite stonking as a payoff.
(reckon that as its an MPI with slightly better torque, it should be slightly more efficient than the CL ... which is already impressively frugal if you take it fairly easy ... its official figures are worse as it has a lot shorter top gear and probably was driven a bit more enthusiastically on the test)