Fast Idle + Vacuum Lines S2 16V

[robsangster]

Ok Have just finished a fairly major project - namely an engine replacement on an S2 - changing all the usual bits inbetween.
Overall it has gone very smoothly indeed and she is running superbly, which given that almost everything has been apart, we're quite surprised by!
However she currently has a high idle. Cold around 1600rpm dropping to 1300 once warm. No fluctuations, hesitation etc etc. On the road she performs faultlessly making me think its nothing too major (fingers crossed)
Haven't had a chance to start going through the list of check points - this weekend sees that - but thought I might throw it open to suggestions.
Obviously air leaks, TPS and the like will be first ports of call, But my first question is this, namely because the vacuum lines had already been disconnected and im not sure on the correct routing.
The PET shows a Y piece coming from the Pressure Regulator (rear of fuel rail nearest to firewall) - clarks just shows a bend - both versions lead to the manifold Y (as does the line from the damper)
Can anyone tell me what theirs does? A simple bend connector from the regulator - or a Y and if its a Y - where does the third section lead to - if anywhere?
I current have this
Line from Damper and Regulator joining at a 'Y' at the intake manifold.
I also have a line from the vacuum valve to the Throttle body.
Point to note this doesn't go via a thermo valve like the coupe Page 84-86 of PET - Thats it

The other vacuum line dealing with heater valve is all hooked up correctly and working fine - so we have no confusion there!

Sorry if this has come up before - I couldnt find anything and unless Im missing a trick - the PET and Clark show slightly differing situations.
Its a 1990 Cabriolet by the way
Any help with the Vacuum lines question - or thoughts on general high idle greatly appreciated - prior to our weekend check list!

Regards all

 

[david924s]

Not sure if this is for an S2 but it may be useful
http://www.944online.com/pdf/techstiksized.pdf

 

[alwigley]

DME temp sensor failing can cause high and/or low idle issues. Mine switched from high idle that reduced a bit when warm, to eventually refusing to idle at all - disconnect the lead from it when she's running and she may surge/settle down, indicating a problem.

Think your vacuum lines are setup exactly as my 2.5na - no idea if the S2 is different.

 

[robsangster]

Thanks for the thoughts so far....DME Temp sensor - not the culprit!, had a spare, no change!

 

[JamesO]

If it runs well, I would be inclined to look at the idle control valve/ wiring.
The other thing to check is that the throttle plate is actually closing when you take your foot off the throttle.

 

[alwigley]

If the ICV is sticking, you could try squirting some air intake cleaner through with the engine running - first from the air filter housing which should help cleanup the MAF (cue usual comments on it's not a MAF.....), then loosen one of the jubilee clips on the air intake hose, and run some in downstream of the the MAF. I know some folk gte funny about using stuff like this, and yes I do prefer to strip down and clean parts properly, but the ICV is a pain in the neck to get to !

The pukka manual has a whole troubleshooting section on how to test the fuel injection components, including the ICV, and spent a couple of interesting hours with a multimeter a few months back trying to find my dodgy idling problem. Worth getting a copy and following the Bosch trouble shooting procedures based on the nice fault chart they include !

 

[robsangster]

Ok, almost slightly embarrassed to admit this but the high idle was my own doing!
During the renovations a lot of extra work was undertaken on other items - including stripping and completely rebuilding the throttle body (replating, vapour blasting etc etc). When I put it back together, clearly I omitted to check the stop screw was wound back enough to enable the butterfly to fully close and indeed the TPS to 'click' off...... school boy error i know but with so much to do clearly i forgot to check the stop position. I whipped the body off and wound the screw back a few half turns and low and behold the TPS clicked and although only a nats - the butterfly closed a fraction further. Reassembled - purring bang on 850rpm! Cost to fix zero, satisfaction 100%. Thanks to those who chimmed in.