Fast Cold Idle

[Griffer]

I think this has been discussed before but cant find the thread.Started the Griff 400 and all well until I touched the throttle, now idles over 2000rpm, the plenum throttle is closed fully, stuck stepper motor?
Did this once before months ago but cured itself.
Any advice guys?, any info gratefully received.
Thanks in advance,

Griffer

[zippy500]

Mine does that. Havent got a clue what it is but try this cos it works with mine. Just switch off engine after a few minutes of fadst running and start again a few seconds later and it may return to 1000 ish RPM. Im gonna get it investigated next service. very strange, its as if the auto choke system gets stuck.
There is an extra cold start fuel injector so this may be a bit iffy.
Ive cleaned stepper motor and all the other options but still it does it every now and again.

Hope this helps. Let me know if it works.

[GreenV8S]

quote:stuck stepper motor?

Could well be, when did you clean it last?

Cheers,
Peter Humphries (and a green V8S)

[Griffer]

Zippy500, thats exactly what mine did before it cured itself last time, GreenV8S I last cleaned stepper about 6 months ago and will do it again tonite, idle now over 2500rpm ,will post findings if I find anything obvious,any other ideas anyone?
Cheers,
Griffer

[GreenV8S]

quote:There is an extra cold start fuel injector so this may be a bit iffy.

You may be thinking of V8 Wedges which use the thermotime gizmo and an extra injector, the V8S and all later V8 models use mapped cold start enrichment instead.

Cheers,
Peter Humphries (and a green V8S)

[zippy500]

Oh right, whats the little thing at the front of the plenum chamber then. I thought it was an extra injector.

[GreenV8S]

quote:
Oh right, whats the little thing at the front of the plenum chamber then. I thought it was an extra injector.

Must admit I haven't looked at the front of my plenum chamber for several months (!) but I don't remember seeing anything there, where the Wedges would have the cold start injector. In that general area there's a fuel temp sender in the fuel rail, a coolant temp sender in the block, vac advance line runs past there along with a couple of breathers, but nothing I can think of that is attached to the plenum. So I don't know what thing is. But I'm reasonably sure it isn't a cold start injector! I'll have another look next time I have the bonnet up, but the way the weather is looking down here that won't be for some time!

Cheers,
Peter Humphries (and a green V8S)

[Griffer]

Good news,fixed it,big air leak at the stepper motor as it was loose!Cleaned the seat as well as the tip, tightened it up properly and all is well.
Cheers,
Griffer

[robperrie]

Mine has starting doing that...where is the stepper

[jeffgleed]

I also have a similar problem (except mine does it when it's warm as well even after I had the control valve replaced). Got this reply from TVR Power (god bless them)

First test you need to do is a cylinder leak down to establish all the valves are seating correctly,to me the problem seems like you have a severe intake air leak,are you sure the control valve is brand new?,the other option is to disconnect your ecu for 20 minutes then reconnect so you erase any glitches stored in memory,I personally feel you have a air leak either around the injector seals or intake manifold gasket nothing to major to worry about just annoying.

Then when I asked about ECU:-

Left hand side footwell pull carpet down you will see a large connecter disconnect for about 15 minutes the re-connect,turn ignition on for around 3 min glitches sorted.

I haven't been able to try any of it yet cos it's either sunny and I am driving it or dark/raining and it's too horrible to go out. Might try this weekend

[Griffer]

robperrie, the stepper is at the rear drivers side of the intake plenum,use 1/1/8" spanner or adjustable to remove after undoing the loom connector,clean the conical tip of all carbon and the seat in the plenum with a bit of rag on a stick, dont scratch it though.
There is a thin sealing washer on the stepper and thats where mine was leaking.Dont overtighten or you will bust it. Good luck.
Griffer

[james]

The sensor sticking out of the plenum is the air temperature sensor.

If you found that cleaning the stepper motor used to work, but it doesn't any more. You might find that the stepper motor is actually faulty. It has been known, and no component is immortal

Any intermittent problem is usually the forerunner of a major problem. Get it looked at by somebody who knows sooner, rather than later.

[tubbystu]

My V8S does that occasionally - I asked Mike at Raven (near Gatwick) who does the servicing and stuff to look into it. He's ex-main dealer technician and now prepares and races Sdi Vitesse's, so "should" know his engine stuff. He says it's due to a resistance mismatch in the loom, but will need more investigation. When I find out I'll post the details.

The turn it off, wait two or three seconds and retry seems to work, but it is a bit of a fag.