High idle (3500rpm) on startup

[istoo]

My S2 111s I took to work today (van in for service) not run for 3-4 weeks and the idle was stuck at 3500rpm where it stayed for nearly he whole way into work, 12 miles and did the same on the way home...

Car is going to winter home his week, usually there by now but I have been overseas. Lives under a Car cover normally

Suggestions?! Damp in idle stab valve? I replaced that last year.


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[robin]

Most likely a manifold leak or similar unexpected air path; 3,500 is quite high revving for a stuck air valve, but possible. If you turn the ignition off wait 30s, then on, then pump the throttle up/down full travel 10 times, then turn ignition off again and wait 30s, does it "fix" it. Also I assume your engine really is revving high rather than it being the tacho indicating a high RPM but engine idle is normal?

Cheers,
Robin

[robin]

P.S. You can tell whether the air valve is the problem or not; remove the short rubber pipe from air valve to throttle and then block up the air valve inlet with something (you could clamp the pipe shut, also, but be careful not to nick it). If the engine still revs strongly then the air path is elsewhere; if it stalls, or at least returns to low idle, then it probably is the air valve.

Cheers,
Robin

[istoo]

Most likely a manifold leak or similar unexpected air path; 3,500 is quite high revving for a stuck air valve, but possible. If you turn the ignition off wait 30s, then on, then pump the throttle up/down full travel 10 times, then turn ignition off again and wait 30s, does it "fix" it. Also I assume your engine really is revving high rather than it being the tacho indicating a high RPM but engine idle is normal?

Cheers,
Robin

it is revving high as i needed my foot on the brake going through 30's to stop it accelerating!
I suspect i have an air leak path as it is, post MAF i guess. something to do over winter time whilst in storage...

i did try the reset, and no difference Learned that last year!

[istoo]

P.S. You can tell whether the air valve is the problem or not; remove the short rubber pipe from air valve to throttle and then block up the air valve inlet with something (you could clamp the pipe shut, also, but be careful not to nick it). If the engine still revs strongly then the air path is elsewhere; if it stalls, or at least returns to low idle, then it probably is the air valve.

Cheers,
Robin

it did this last year about october when it was cold and damp as well. never done it since. i replaced the idle valve last year with a new one from eliseparts so I am assuming its not that, but it 'could' be a nicked/perished bit of plumbing. what is the lifespan on these anyway, they actually look reasonably good.

I have a spare Throttle Body with Potentiometer in the garage, i was going to port the intakes over winter time, i may fit this as i winter if the potentiometer is sticking... i do have a MEL light on, anyone local for an ECU read?

[Dominic]

A quick and easy way to check for a leaking inlet manifold; get some carb and airfliter cleaner (this stuff; http://www.amazon.co.uk/Wynns-1831014-5 ... or+cleaner ) and spray it on the inlet gasket while the engine is running. If the revs fluctuate, you have a leak. That is how I diagnosed my leaking inlet gasket.

[istoo]

Spot on, thanks [SMILING FACE WITH OPEN MOUTH AND SMILING EYES]


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[Ferg]

If you're in at CMC ask Calum what happens when you do that on a car with a hot manifold! :lol

[BigD]

A quick and easy way to check for a leaking inlet manifold; get some carb and airfliter cleaner (this stuff; http://www.amazon.co.uk/Wynns-1831014-5 ... or+cleaner ) and spray it on the inlet gasket while the engine is running. If the revs fluctuate, you have a leak. That is how I diagnosed my leaking inlet gasket.

That's what I was going to suggest too. Good tip.

[istoo]

Started up today to take winter storage, brim, 1200rpm solid idle... Perhaps contraction when too cold on some plumbing somewhere, weird... I love the idiosyncrasies


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