High idle - Tried everything :|

Hi

When starting cold my idle starts off around 1000 rpm and rises to 1800 rpm within 1-2 minutes, which is my problem.

Info about my engine: Complete stock 1.8 DX GTI with a 52mm throttle body.

Things ive done / tried

Idle screw - New gasket + grease - screwed all the way in, as closed as it can be.
AAV - Bought a new, nothing happened
WUR - Control pressure, system pressure, hold pressure within limits of the books.
Mixture adjusted.
Timing adjusted
Old original throttle body, nothing happened.
New ignitionplugs
Sprayed "Quick Start" around ALL hoses, intake seal, valves etc etc - Everything has been sprayed in various places without any reaction.
Brand new injectors
Brand new injector hoses from HEL

No luck what so ever.. cf_emoticons__BangHead:Anyone have any suggestions ?

Have you looked at the 'Suction Jet Pump' which sits between the inlet manifold and the brake servo. It's a simple bit of engineering designed to increase the vacuum at the servo so it works better, but it has rubber components inside which can degrade with time.

It's the 3 way split in the hoses near your throttle body and looks like this.



A friend recently had a similar issue with his idle, and after a lot of headscratching and replacing bits like you have, we narrowed it down to this component. We swapped his one and my one over and the effect was my car idled at about 2000RPM and his was perfect, having previously been idling too high. When the rubber inside these breaks down it effectively allows air to bypass the throttle which is what it was doing.

If you want to test it disconnect the hoses that go from it to the throttle body and seal the ends by plugging them with a bolt or similar, then see if your idle is OK. You can't leave it disconnected as if you do you won't have any servo assistance, but at least you'll then know what the problem was.

Mike. 

Im not sure i have that piece.

This is my engine bay : http://bil2.webgallerier.dk/galleri/fuldskaerm/556/2778735-vw-golf-1-gti

Do you mean this piece ? : https://encrypted-tbn2.gstatic.com/images?q=tbn:ANd9GcTI3j-JMSEo4BXy3m-wafA7892_IJGNpJhuvWXpoNGjcSesDowiYw

^^ that's the bit. I can see it in your engine bay as well. :-) 

Funny thing is when i remove the AAV and the Y-Piece i linked to, plugging all up my idle is perfect when warm

But ofcourse starts VERY rough due to lack of the AAV

Replace that 'Y' bit, it;'s not just a simple junction, that's the suction jet pump and if your idle is perfect in its absense, then that is your problem.

Mike.

Mine came apart slightly and caused the same issue. I would go with Maniac on that one.

http://vwgolfmk1.org.uk/forum/index.php?page=topicview&id=your-mk1-golfs_2%2Fblack-bullet-ngh705y&start=20#post_864731

If it is this piece, its inside that something has gone wrong.

Ive had it torn apart, cleaned and put back together with clamps in all ends to make sure it couldnt suck any false air.

Maybe the small hole in the black piece inside the grey piece is too big ? ill try and fiddle with it today.

have you checked you get 12v on the AAV plug when engine is running?

Yeah, ive also checked that the AAV closes with 12v over time and checked that the AAV closes with heat.

W65_Pirelli said

If it is this piece, its inside that something has gone wrong.

More than likely, it looks like this inside.



If any of the rubber bits have degraded it can let air flow in directions it's not supposed to or too much air flow all together.

Mike. 

possible simple fix for this is insert a brake servo non-return valve on the left outlet?

hmm not if the 2 flaps can bleed air between the chambers… maybe a Y splitter, 2 check valves and some kind of reducer for connection F

alternatively just bin it all off, the 16v manages just fine without? i guess you might want a bigger servo though, 9" mk2 unit and 16v master cylinder perhaps

edit: mk2 kjet 8v has one as well, not sure why the kjet 8v needs oen yet kjet 16v does not  

rubjonny said

possible simple fix for this is insert a brake servo non-return valve on the left outlet?

hmm not if the 2 flaps can bleed air between the chambers… maybe a Y splitter, 2 check valves and some kind of reducer for connection F

My friend has temporarily solved his by plugging the one labelled "From F connector" on that diagram with a bolt, that reduced the air flow sufficiently and put his idle back to normal. The bummer with this part is VW no longer make them.

Mike.

found this:
http://www.deroure.com/partinfo.asp?MAK=3&MDL=24&TBL=2302&SMA=0&SMO=0&ST=&SC=0&PBID=65685

I found my problem.

I had changed my throttle body to the 16v large ones.

Seems there were too much air slipping through the butterflies.

I had initially switched back to the original one without no change in idle, back then after fiddeling another 2 weeks with the problem i had another go with the original throttle body and somehow this time it made the change.

rubjonny said

found this:
http://www.deroure.com/partinfo.asp?MAK=3&MDL=24&TBL=2302&SMA=0&SMO=0&ST=&SC=0&PBID=65685

Just bought one of these - for info was £17.03 including insurance and shipping. It checks out on Partsbase as the same part number for the MK1, despite being listed for Porsche on this site.

For the money it's worth the stab to have a new one - thanks for the link John!  

Just ordered one of these as well - fingers crossed this will work as my idle is getting worse !

Looks like DeRoure are out of stock, I've left this open with them in the hope that Porsche receive additional stock but DeRoure thinks that Porshce may source this from VAG anyway, in which case we are kippered !

Yeah I got an email from them shortly after ordering saying that it's on back order from the factory with no supply date, so no idea how long we'll wait. I'm in no hurry so it's ok!