I think I've blown a gasket...but which one?!

[powerhand]

So, went to Castle Combe yesterday and thrashed my Mk2 16V GTi around for a few hours.  Excellent fun and with the 9A 2.0l bottom end, annoyed a few who struggled to keep up! 

Anyway, this morning went to start her and a few problems...

1. Initially idling a bit erratically, between about 900 and 2000 rpm (very nearly stalled itself).  Then warmed-up and not too bad.
2. A bit hesitant under acceleration and stuttery on the move in any gear under around 2000 rpm.
3. Loud hissing noise under the bonnet around the area of the throttle, but seems to quieten with increased revs - very loud at idle.

Having searched through Haynes Fault Finding, all the symptoms seem to lead towards a gasket (inlet, exhaust or head).  Anyone know which would be more likely to go, how to diagnose the problem further and how to fix it?

All input very gratefully received - if it's really broken, the wife won't let me go on the track again 

[Horney]

Sounds liek either an inlet manifold gasket has gone or one of the vacuum pipes has become detached.

Have a good listen (Mayb e use a straw to help) and try and pin point exactly where the noise is coming from. Should be an easy and cheap fix though.

Glad you had a good time, I'm down there myself next friday in mine!

Nick

[danny_p]

wave an unlit blowlamp around,  when enigne speeed increases you have found the leack

[Diamond Hell]

It could be the exhaust manifold gasket, or the downpipe.

Check the pipes on the ISV, too.

Sounds like some air's getting in somewhere.  Get it sorted ASAP as it might make the motor run lean, which will kill it pretty sharpish.

[Paul86S2]

Advice as everyone else's, check you vacuum pipes for one come adrift or split.

Paul

[powerhand]

Thanks guys - I'm going to have a proper look at it tomorrow and see what I can find!

[powerhand]

After a bit more investigation with my unlit blowlamp...

wave an unlit blowlamp around,  when enigne speeed increases you have found the leack

danny_p...great advice and worked a treat!

I found an open hole in the throttle switch.  I'm sure a more seasoned Dubber would have noticed this straight away, but I'm still learning! 

Covered the hole with my finger and idle settled down immediately - so gaffer taped it up for the time being and got an idle speed of around 1100 rpm - very (non-) scientific.

In the picture, you can see what I've taped up (yellow and green stripey tape).  I think it's missing the idle adjustment screw and washer...is this right?







Does anyone happen to know if I can get this from a VW dealer and if so, what part number it is?  Or is it a trip to the local scrappies?

Thanks again for all the advice! 

[Horney]

Yup that's the adjustment screw all right. Dealer may well be able to get them or a scrappie etc.]]

Nice strut brace!

Nick

[Conker]

Blimey - Bit random to have lost your idle screw!!  Not sure how that could have fallen out unless it was only screwed in a few turns??  Did you manage to drive home okay?  If so, I would have a really good look around under the car, as it might have fallen out on the drive etc. If it fell out while driving you would definitely notice.

Last time I asked, VW didn't stock this part anymore.

It might be quicker to buy a whole throttle body off ebay - they are not that expensive.