New member seeking help already

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New member seeking help already

December 09, 2023, 07:27:33 PM

Hi everyone

Iv got an '89 golf gti 8v with an issue.
Basically it starts up fine and runs perfectly until it gets up to temperature then the throttle response drops and eventually it cuts out completely and won't start again until it has cooled down.
I'v taken it to a couple of garages and they come back with the ECU is faulty so ordered one and its the same problem.
Any help will be massively appreciated.

cheers
Luke

Re: New member seeking help already

Reply #1 – December 11, 2023, 10:43:58 AM

Hi Luke,

Do you know what tests the garages did on your car?
Could be a couple of things, neither of which would be an ECU, if they're dead, the car just wouldn't fire in the first place.

First thing I'd do is a compression test, I've had it in the past where a car would start when cold, but when the car warms up, the tolerances open up and then the compression drops to where it couldn't fire.
It also could easily be the timing/idle is not set up correctly.

Where abouts are you based? Maybe you're close to a decent garage who can diagnose it properly.

Re: New member seeking help already

Reply #2 – December 11, 2023, 08:23:46 PM

Typical behaviour from a general garage these days. If they can’t plug it into a computer and get a code they’re lost and don’t want to go down the rabbit whole on diagnosing but it takes time they might not be able to charge you for if they can’t actually provide a solution :-(

Re: New member seeking help already

Reply #3 – December 11, 2023, 10:03:18 PM

Quote from: Monkey on December 11, 2023, 10:43:58 AM

Hi Luke,

Do you know what tests the garages did on your car?
Could be a couple of things, neither of which would be an ECU, if they're dead, the car just wouldn't fire in the first place.

First thing I'd do is a compression test, I've had it in the past where a car would start when cold, but when the car warms up, the tolerances open up and then the compression drops to where it couldn't fire.
It also could easily be the timing/idle is not set up correctly.

Where abouts are you based? Maybe you're close to a decent garage who can diagnose it properly.

Yeah I couldn't see how it was the ECU but both garages said the same thing. so thought I would try it.
The garages did a compression test, sorted out the timing, iv had new leads, spark plugs, new fuel pump filter etc. It runs at 900 revs until it gets warmed up.
Im based in Norwich one of the garages was a vw approved place but like Eddy said if the garages can't plug the car in they struggle now.

Re: New member seeking help already

Reply #4 – December 12, 2023, 09:11:31 AM

Ok, that RPM is a tell-tale straight away.
On warmup is should be more like 1200rpm, only dropping to 900 once it's been fully warmed (fan kicked in and out).
Good that the compression is good, did they test is warm or cold do you know?

Also, when it gets hot and dies, does the car re-fire and stop, (can you keep it running with throttle?) or does it just not fire?

Typically, a car only needs 5 things to operate:
Spark
Fuel
Timing
Compression
Air

Just work through them when the car starts to play up.

One other thing, I'd be very suspicious of the garage that said they had set up the timing.
In order to set it up properly, the car has to be at full running temperature, something yours cannot do right now.

Re: New member seeking help already

Reply #5 – December 12, 2023, 09:30:30 PM

ah okay so timing is still out then.

So when it gets hot the revs drop if I push the throttle the response drops massively then it just cuts out even with the throttle fully down the revs don't pick up and if just dies and will not start until its cooled down.
I was told the compression test was done cold and hot (well as hot as they could get it)

Re: New member seeking help already

Reply #6 – December 13, 2023, 09:30:15 AM

Ok, good info.
At least we know that there should still be compression there.

The fact that the engine dies faster when hot can mean a couple of things:

Your air fuel ratio is off and introducing more air to it is throwing it off massively, causing it to die. - Try disconnecting the air flow meter and see what difference that makes.

Your fuel pump is dying and stops working when it gets hot, so you're just running out of fuel faster when you try to use more. - Pop the screw on the end of the fuel rail off, stick a hose on it into a bottle and see if you have fuel when attempting to restart.

Re: New member seeking help already

Reply #7 – December 13, 2023, 12:48:26 PM

I had a similar problem might not be the same but my fix turned out to be the air intake to the inlet manifold was not fitted correctly. Looked ok but the clamp on the large end was loose.

Re: New member seeking help already

Reply #8 – December 13, 2023, 03:40:15 PM

Very true, if you're sucking in unmetered air, the ECU can't send the correct fuel in.
One way to check is to spray a little brake cleaner around the rubber pipes, if the revs pick up, you've got a leak there.

Re: New member seeking help already

Reply #9 – December 17, 2023, 01:59:57 PM

okay so finally had time to look at the car

Iv disconnected the air flow meter and the car just cuts out straight away.
the flue pump carries on running after the car dies then it turns off after a few seconds then when i turn the key with a hose on the fuel rail I got fuel coming out and I can hear the fuel pump priming.

Iv checked all connects on the air intake and they were all tight and I checked the condition of the air intake and I couldn't see any cracks or anything like that.

The other thing is its actually idling at 800rpm so like you said if its meant to be 1200 that's massively low. any tips on timing?
starting to not trust garages after they've had the car for 2 months and im still in the same situation.

Re: New member seeking help already

Reply #10 – December 18, 2023, 09:28:00 AM

So when the car is in 'broken' mode, can you restart the car if you keep your foot on the throttle?

Your car should idle around 950rpm when fully warm, when it's cold, should be around 1200.

There is a specific procedure for timing, though it needs the car to be idling when fully warm.
As you can't do this at the moment, I'd mark up the dizzy with a paint pen (so you can put it back if necessary), then loosen it off and turn it when it's warming up.

That being said, it might not be your timing, it might be the idle speed screw, I'd try that first.
In the front of your throttle body, there is a small brass screw to control idle speed (usually covered with something). wind that out a little and see where it gets you.

Re: New member seeking help already

Reply #11 – December 18, 2023, 07:39:50 PM

so when car is in 'broken' mode it won't restart at all even if my foot is on the throttle.
it just tries to start but doesn't until 10-15 mins later when its cooled down.

Okay I'll have a look at the idle speed and see if that does anything.

Re: New member seeking help already

Reply #12 – December 18, 2023, 08:23:58 PM

I don't know much about fuel injection but if this was a carb model I would think the choke was stuck on so could it be something to do with the 5th injector?

Re: New member seeking help already

Reply #13 – December 19, 2023, 12:19:45 AM

Quote from: scs on December 18, 2023, 08:23:58 PM

I don't know much about fuel injection but if this was a carb model I would think the choke was stuck on so could it be something to do with the 5th injector?

correct me if im wrong, but that's k-jet with the 5th injector i thought, an this being a 89, i would assume was pb/pf digifant they didnt have a 5th injector, but please correct me if im wrong, dont recall my old engine having it, an my latest car hasnt arrived yet to go look lol

Re: New member seeking help already

Reply #14 – December 19, 2023, 09:25:00 AM

That's correct, the digis didn't have a 5th injector.
They have a warm up routine where they bring the idle up a few hundred rpms.

If the car won't fire at all when it's in broken mode (I'm assuming it doesn't cough or spit), then we go back to the classic requirements:
Spark - Have you checked this?
Fuel - you've got fuel at the rail, but possibly not through the injector, when it's broken, turn it over a bit and have a spark plug out, see if it's wet with fuel.
Timing - Have a go at swinging on the dizzy when it's broken, but as mentioned, mark it first so you can reset if needed.
Compression - Fingers crossed, this is ok if they've tried it when it's broken - did they give you the results?
Air - Pretty sure you have that

Good hunting