Car Pulling Without any Acceleration

[benadams]

My 98 Chimaera 4ltr is constantly pulling when I’m not accelerating. It will quite happily drive along by itself. I drove all the way through a village last night at 30mph without me pressing the accelerator at all. It’ll even go up a slight hill on its own.

I really have to brake quite hard to get the car to slow down or I have to press the clutch down / put it into neutral.

If it’s in gear when I brake then when I come off the brakes once slowed down, you can really feel the acceleration kick back in even though I’m not pressing the accelerator.

I know the stepper motor is a common problem but these seems like it could be something else?

Any thoughts?

Thanks

[SpeckledJim]

Dirty/weak/maladjusted closure spring on the throttle?

[Belle427]

What speed does it idle at?
As above check the throttle is returning to its stop first.

[sixor8]

Dip the clutch whilst moving and it should hold at about 1200 rpm for a second or two (to aid gear changes) but if it doesn't then drop back to 1000 rpm, I'd suggest the stepper motor, IMHO.

[benadams]

It’s at 1200 for a couple of seconds then comes back down to 900/1000 when stationary. Although it has been doing a strange revving thing on occasion as well, a bit like this…

https://www.youtube.com/watch?v=CiYqQQL8XK8

This isn’t my car but I saw it posted on here a little while ago.

[blaze_away]

Have you set the base idle correctly ? Needs to be around 700 to 750 with the hose to the stepper fully clamped shut. If thats not set properly the stepper has no hope.

Edited by blaze_away on Saturday 17th June 22:02

[benadams]

Looking back through the large file I got with the car, it looks as though the Stepper Motor was replaced back in 2016 and it’s only done 3,000 miles since then.

[Fifty]

benadams said:

It’s at 1200 for a couple of seconds then comes back down to 900/1000 when stationary. Although it has been doing a strange revving thing on occasion as well, a bit like this…

https://www.youtube.com/watch?v=CiYqQQL8XK8

This isn’t my car but I saw it posted on here a little while ago.

That’s my vid. Never really got the the bottom of it but I did swap out the stepper for a bone fide Lucas (?) one and it has been pretty much ok since then. I suspect the old stepper was possibly a cheap Chinese one. Unable to prove conclusively one way or the other though - my thought pattern was ‘it works now so don’t fk about with it’

[benadams]

Thanks for the video 👍🏻.

The file said the Stepper cost £110 so I’m guessing it’s a bonafide one rather than a cheaper version.

[SpeckledJim]

Fifty said:

benadams said:

It’s at 1200 for a couple of seconds then comes back down to 900/1000 when stationary. Although it has been doing a strange revving thing on occasion as well, a bit like this…

https://www.youtube.com/watch?v=CiYqQQL8XK8

This isn’t my car but I saw it posted on here a little while ago.

That’s my vid. Never really got the the bottom of it but I did swap out the stepper for a bone fide Lucas (?) one and it has been pretty much ok since then. I suspect the old stepper was possibly a cheap Chinese one. Unable to prove conclusively one way or the other though - my thought pattern was ‘it works now so don’t fk about with it’

Can you hear/feel it index as you turn the ignition on?

[sixor8]

Isn't when you turn the ignition off? The stepper motor runs back completely and the chattering is it running out of free movement.