Warm starting problems

[wasted]

Hi all (again!). Having sorted out my charging problem (new alternator solved this - many thanks to colsy and bensspares), I now need to sort out a niggling little problem that has been present for some time now.

The car starts from cold first turn of the key, and idles with no issues at all (there are rare occasions, when very very cold, that it needs a little press on the pedal to get it idling smoothly). However, it does something rather strange when restarted after stopping from hot and leaving for 10-15 minutes.

Note that the engine idles perfectly when the car's hot - no dipping, no variation on revs. However when restarted after this short wait, it struggles to idle, generally sitting around 700-750rpm. When pulling away, there are no issues - power is fine, engine responds normally. However as soon as the clutch is pressed down (for example pulling up to a junction), the revs dip way down and generally the car stalls. If it doesn't stall, the ignition light and oil light flash briefly, and then it struggles back up to about 700-800rpm.

After about five minutes of steady driving, the engine returns to normal. However on occasion, during these five minutes, it will stall totally and then will not start again - the engine turns fine, but it doesn't catch at all. If I wait for a minute or two and then retry, it fires straight back up again.

Current suspect is the AAV, which has been hissing for some time - if the pipe from it is squeezed when the car's hot, the revs dip and then stabilise. However if this were the culprit, I'd be inclined to expect it to race (due to being too open hence too much air) rather than die.

Any clues?

[bensspares]

hi wasted,

i dont know whether this is a carb or inj engine but i guess from the symptom its injected.......my 2 pence worth says its the injectors leaking, its realy common after 1250000 miles ish.

ben

[wasted]

Yeah, it's injection. So... leaky injectors = new injectors? Or can I have them cleaned?

[bensspares]

you can have them cleaned but its pointless...second hand are or will be going the same way....the reason the car is difficult to start is the vibrator pins inside the injectors are nfu and arnt closing the injector when engine stopped allowing feul into the cylinders thus causing flooding on starting,when engine cold and not run for several hours feul has had time to evaporate thus starts easily.

worth checking cold start isnt leaking but my money still says injectors..

all i can suggest is buy new from euro carparts they gave the best price and service....and the injectors were bosch and complete with seals and cost £160 aprox....this will be the best money you will ever spend on your scirocco...

[wasted]

Given that the car starts normally from hot but won't idle though, wouldn't this indicate something else? Once the engine's fired, I'd imagine the excess fuel would quickly be eliminated with the exhaust gases. I'd imagine leaky injectors to cause problems starting from hot, rather than stalling once running.

[bensspares]

depends....if injectors leaking could be flooding engine at idol revs.....another candidate is the wur keeping the mixture rich but my money is still on the injectors....

[wasted]

Well I have a spare WUR, and I'll be cleaning up / replacing the AAV soon, so I think I'll try those before forking out for the injectors.

Out of interest, would a vacuum leak somewhere in the system cause these symptoms as well?

[PeteGLi]

.....Current suspect is the AAV, which has been hissing for some time - if the pipe from it is squeezed when the car's hot, the revs dip and then stabilise. .....Any clues?

The engine speed should remain unaltered when the engine is hot.

Have you checked it has voltage at the plug? These wires are notorious for breaking.

Have you checked it operates correctly when the engine is cold?

Haynes is remarkably good on this point.

[bensspares]

yes always iliminate all the cheap and basic candidates first, a good clean out will do no harm and hopefully yeild the solution.once youve iliminated the basics then on to those injectors.....

ben

[wasted]

Pete - I know it shouldn't dip, and it hisses constantly, so it's clearly not operating as it should be. I suspect it's stuck at least partially open. It'll get a good soaking and cleaning in carb cleaner asap. Do you reckon this could be causing the symptoms?

[bensspares]

if the aad was jaming open the engine revs would be constantly above 1000 to upto 1500rpm....if revs drop when pinched when warm then the idol will have to be set low to compinsate for the airdevice staying open.it could be a split hose or bellow conectors on the intake side making it weak an could explain the hissing....also intake manifold gasket leaking.remember that the airdevice only bypasses the throttle it has no bearing on the engine atall.

[wasted]

That matches, because the adjustment screw on the injection system is screwed right in to maintain a relatively decent engine speed at tickover. That'll be my first thing to sort then - thanks!

[wasted]

Hi all... Planning on removing the AAV and WUR today and cleaning them up to potentially sort some issues out, but I've been doing a little research over on the Mk1 Golf forums this morning and found this:

...if the car was left when warm for about 10-15 minutes, when I came to start it again, it would fire up, then die - especially quickly if I blipped the throttle. This could be completely cured by disconnecting the electric feed to the fifth injector. When the colder months came along, I thought I would try to look into this thinking it was the thermotime switch (TTS).

Having read a bit more, it seems that if the TTS is faulty, the fifth injector ends up being powered even when the engine is running (and should only receive power when cranking). I'm planning on testing this later on by disconnecting the fifth injector when running from hot. Anyone know if this is feasible? How easy is it to source and fit a replacement for the TTS on a DX engine?

[wasted]

Well, did a bit of work on Sat and Sun trying to remove the AAV and test the fifth injector - fifth injector seems fine, as when the injector is disconnected with the engine running, there's no change in engine note / idle speed.

The AAV I'm having serious issues with when trying to remove, as the top hex bolt is virtually impossible to access without a very strangely-shaped hex key... Current plan is to use a hex socket and a fairly long ratchet up the back of the engine behind the bulkhead. I'll come back to that :/

Also sprayed the various vac hoses around the engine bay with carb cleaner and detected no leaks at all, which is nice.

Current suspects are still AAV causing over-weak mixture when started from hot, or the WUR being faulty / stuck and preventing the mixture from changing. Only thing that doesn't make sense is that the engine only has trouble when restarted from hot, not when running after heated up from a cold start.

Other options? I'm starting to think this could be the ICV now... Injectors still don't seem to match, as the engine is not lacking in power when restarted, and starts first time; it just idles low and cuts out if the revs drop suddenly.

[leamington 1642]

hi mate, did you get it sorted? i have the same prob!mine wont start when its been for a good long run,when it cools down its fine?????.