tickover / low rpm

[petea]

before anyone says it....the stepper motor and housing have been cleaned!

Car is a 94 M, Chimaera 400, 32 K miles.

car has always accelerated fine but tickover and low speed / low rpm driving is eratic / lumpy....

recently replaced the plugs, leads, coil, etc. replaced the tune resisitor as the dealer history said it was incorrect - turns out it was correct type but put the new one in anyway. un-plugged the ECU to reset.

car now seems fine expcept for the tickover / low rpm. (still!!!) The car ticksover at 2000rpm ish and hunts for about 10 seconds then very slowly drops to what you would expect. on cold start up the car practicaly drives it self along the road without me having to touch the throttle!

Have tried setting the idle as per the bible but may have made it worse!

Any ideas?

Thanks in advance for any replies.

[GreenV8S]

Air leak?

If you can get the idle to settle down at a sensible level, disconnect the electrical connector from the stepper motor. If the problems all go away, it's the stepper motor which is causing it. If no difference, you can rule all that side out and concentrate on looking for more traditional problems

[petea]

Thanks V8S

Got home from work and did what you suggested...disconnected the stepper motor and the revs increased to about 3 / 3500 rpm. Re-connected it and the revs slowly dropped but not the the level i would expect...about 1500rpm.

Checked for an air leak around the stepper motor and the pipe but they seemed fine.

Tried to adjust the idle using the screw in the manifold as per the bible - i managed to turn the screw in fully and there was no change or very little to the revs. If i un-screwed it the engine made a whistling sound not unlike a jet engine.

At the minute the screw is un-screwed by half a turn (rather than the 2 1/2 turns stated in the bible)and it seems better but i wonder if all is well? I am going to clean it out the best i can at the next opertunity in case it is bunged up or dirty.

Any thoughts anyone?

[GreenV8S]

You need to get the idle steady before you disconnect the stepper motor, if you catch it in the middle of 'opening the throttle' to catch a drop in revs then it will leave the 'throttle' too far open giving you too much revs.

[BeVo]

I have the same problem, only started a few weeks ago. I have not yet got round to fixing it but I iwll let you know how it goes. ..

[GTvr]

Just a thought have you checked the throttle cable for wear or tried readjusting the tensioner.

[parrot of doom]

Pull the stepper out and look inside the chamber. Check the end is nice and smooth, mine isn't and its the cause of much idling problems. Waiting for a new chamber now......