Bloody Idling

[Carrmonkey]

Evening guys
So recently I was recovered by the AA with miss firing back firing and general spluttering. Thanks to advice on the forum I have since changed the dizi cap, rotor arm, plugs , leads, throttle pot and idle speed control valve. The car seems OK now and the backfiring symptoms have gone BUT the idling is all over the place. If i connect the idle speed control valve when I start the engine the idling fluctuates heavily between 2000 & 1500 rpm for about 10 seconds and then settles to 900 rpm. As soon as I drive the car she starts to rev again at 1500 - 2000 rpm which involves a bit of clutch control.

If I unplug the idle speed control valve the car drives absolutely fine no problem.

I have checked for an air leak but cant seem to find anything obvious

Id appreciate any ideas

Cheers
Mark

[Griffinr]

Check for air leaks and also check that the throttle butterflies fully close at idle. The recovery man may have fiddled with the idle screw.
Rob.

[dezglidden]

Mine was almost exactly the same. Was the wiring, particularly from the iscv. Replaced and sorted.

[blues3]

Try these links below.

http://www.pistonheads.com/gassing/topic.asp?f=6&a...

http://www.pistonheads.com/gassing/topic.asp?f=11&...

If I was slowly rolling to a stop the engine revs would increase to around 2500 (which usually incurred wry, "oh a boy racer" type looks from the car next to me. As soon as the road wheels stopped turning the car would idle like a good 'un.

Fault was a scruffy square wave output from the speedo sensor on the gearbox playing havoc with the EEC.

Don't recall if there was a need to reset any fault codes.

Hope that helps.

Dave

[Top Gear TVR]

I get some if this. After a longish run my idle will increase to say 1200 to 1400. Also holds revs high between gears ( slow to fall) after similar distances. Might give the flaps a check / clean?

[Carrmonkey]

Thanks for your advice guys

I have checked the wiring and changed the plug on the ISCV. The problem is still there.

I noticed a strange grey tube connected to the cables coming off of the ISCV. Does anyone know what this is? Is it some sort of resisitor?

Can these things fail?

Thanks Mark

[mep12345]

Probably the diode, see here

[Carrmonkey]

Good stuff thanks for the link.