Idle speed adjustment?

[peter m]

Ever since I have had the S2, the engine runs fine, and ticks over fine. However, if I am in a crawing traffic jam and I coast along at a few mph out of gear, the revs drop from the normal idle speed (~800rpm) to a lot lower, and return to normal when I stop moving.

I suspect that the ecu is monitoring the speed sensor, and closing the idle bypass valve when I start moving, so the revs drop. So the question is.... Is there a small screw somewhere that I can adjust so I can raise the very low tickover speed up a bit? Perhaps a return set screw on the throttle plate? I just would prefer it if it did not drop so low.

I know the ecu sets the normal "car stationary" rpm.

Thanks

>>> Edited by peter m on Thursday 17th February 13:33

[WildfireS3]

No. IIRC the Idle on the 2.9 is completely controlled by the ECU. On the 2.8 you can adjust.

[KentishS2]

I used to have the opposite, I still do to a much lesser extent after changing TP and wiring loom.

Revs high until I stop but the 2.9 as Chris says is ECU controlled with no road speed sensor, I believe that others have the same experience.

So, why the hell does the car do that?

[bugsy]

Peter
I am racking my brains to remember the sequence and my mechanic is off sick at the moment.
IIRC there is an air screw to adjust the tickover but you have to disconnect the idle valve connection to the ECU first otherwise it just changes it back.

If you know any Ford mechanics, they will know the sequence.

[KentishS2]

KentishS2 said:

I used to have the opposite, I still do to a much lesser extent after changing TP and wiring loom. Revs high until I stop but the 2.9 as Chris says is ECU controlled with no road speed sensor, I believe that others have the same experience. So, why the hell does the car do that?

Any ideas folks?

On why the car should hold a high idle speed of 1100-1300 rpm until the car comes to a standstill?

[bugsy]

[/quote]
Any ideas folks?

On why the car should hold a high idle speed of 1100-1300 rpm until the car comes to a standstill?

[/quote]

How about the idle valve, give it a clean, the butterfly may be sticking




>> Edited by bugsy on Thursday 17th February 16:25

[peter m]

I think the speed sensor from the gearbox does connect to the ECU - I will look in the bible tonight.

Is there any adjustment on the idle valve, or is it a fixed unit?

I have no idea why Kentish's engine does the opposite. Very weird. Can't blame TVR for this one, this is all good olde Ford stuff.

[KentishS2]

Not just me who has mentioned this.

I find that it's not a problem now since sorting the throttle pot and wiring (it appeared to be exacerbated by the TP fault) but since then it idles around 1100 and drops to 850-ish as soon as you come to a halt.

With the prior TP and wiring loom fault it idled at 2600 rpm until I came to a stop and was a real annoyance!

So, the characteristic is still present but to a much lesser extent and in fact it is now very useful whilst moving in slow traffic as you can coast dipping the clutch and then picking up again without touching the throttle.

Plus the engine and exhaust note sound nice at this rpm

[oldred]

KentishS2 said:

Not just me who has mentioned this. I find that it's not a problem now since sorting the throttle pot and wiring (it appeared to be exacerbated by the TP fault) but since then it idles around 1100 and drops to 850-ish as soon as you come to a halt.

Kentish

My V8S does exactly this. I was told by the local TVR dealer it is for tree hugging environmentally friendly reasons. Apparently it is to burn off unburnt fuel in the exhaust. Don't know if this is BS or what but sounds plausable.

[KentishS2]

oldred said:

KentishS2 said: Not just me who has mentioned this. I find that it's not a problem now since sorting the throttle pot and wiring (it appeared to be exacerbated by the TP fault) but since then it idles around 1100 and drops to 850-ish as soon as you come to a halt. Kentish My V8S does exactly this. I was told by the local TVR dealer it is for tree hugging environmentally friendly reasons. Apparently it is to burn off unburnt fuel in the exhaust. Don't know if this is BS or what but sounds plausable.

Sounds good :shrugsshoulders:

[F908 TIM]

Mine does exactly the same as Kevins.It became noticable since I had to muck about with TPs,front wiring looms and new air bypass valve etc,just as his did.
I am on a different TP than Kevin so it ain't that.
Pretty lost 'why' it does it but as long as it does it all the time...then I reckon its OK.
The environment answer is possible I suppose