V8S idle (or not)

[brioss]

This is a problem that is intermittant, for some reason the engine does not like to idle, the revs can just drop off fully and cutout.

I have had a look at other threads and the old stepper motor is always the first port of call.

I have removed the stepper twice and cleaned it and its threaded orrifice.

Take Monday for example, Started from cold , runs a little fast unil warmed up 1200ish. The settles down to about 800-1000 rpm. I drove around all day, and made several stops. When I restarted all was fine. Then towards the end of the day I started the car and it would not idle, I had to rest my foot on the throttle to keep it ticking over, then it did start to idle but the idle was very low 600ish and sometime began to hunt.

The next time I head out for spin all could be well again, Its so unpredictable.

Any idea ?

[oldred]

brioss said:

This is a problem that is intermittant, for some reason the engine does not like to idle, the revs can just drop off fully and cutout. I have had a look at other threads and the old stepper motor is always the first port of call. I have removed the stepper twice and cleaned it and its threaded orrifice. Take Monday for example, Started from cold , runs a little fast unil warmed up 1200ish. The settles down to about 800-1000 rpm. I drove around all day, and made several stops. When I restarted all was fine. Then towards the end of the day I started the car and it would not idle, I had to rest my foot on the throttle to keep it ticking over, then it did start to idle but the idle was very low 600ish and sometime began to hunt. The next time I head out for spin all could be well again, Its so unpredictable. Any idea ?

Sounds like stepper motor. I tried cleaning mine countless time before having to replace it. The shaft of the new one could be pushed in and out very easily, the old one however was very stiff, even after WD40 etc had been poured into the thing.

[GreenV8S]

Check the base idle, the engine should more or less idle (at 500 rpm or so) on the fixed bypass. This is the speed it will run at with the stepper motor in the fully closed position.

[brioss]

GreenV8S said:

Check the base idle, the engine should more or less idle (at 500 rpm or so) on the fixed bypass. This is the speed it will run at with the stepper motor in the fully closed position.

Pete,

How do I know that motor is fully closed , so I can then check the base idle on the fixed bypass, if you disconnect it wont the motor position remain in the same postion ?

Does that make sense ?

[brioss]

oldred said:

brioss said: This is a problem that is intermittant, for some reason the engine does not like to idle, the revs can just drop off fully and cutout. I have had a look at other threads and the old stepper motor is always the first port of call. I have removed the stepper twice and cleaned it and its threaded orrifice. Take Monday for example, Started from cold , runs a little fast unil warmed up 1200ish. The settles down to about 800-1000 rpm. I drove around all day, and made several stops. When I restarted all was fine. Then towards the end of the day I started the car and it would not idle, I had to rest my foot on the throttle to keep it ticking over, then it did start to idle but the idle was very low 600ish and sometime began to hunt. The next time I head out for spin all could be well again, Its so unpredictable. Any idea ? Sounds like stepper motor. I tried cleaning mine countless time before having to replace it. The shaft of the new one could be pushed in and out very easily, the old one however was very stiff, even after WD40 etc had been poured into the thing.

I have cleaned it but not lubed it, maybe I should give it a clean with WD40.

Cheers


>> Edited by brioss on Tuesday 29th March 21:23

[HarryW]

brioss said:

GreenV8S said: Check the base idle, the engine should more or less idle (at 500 rpm or so) on the fixed bypass. This is the speed it will run at with the stepper motor in the fully closed position. Pete, How do I know that motor is fully closed , so I can then check the base idle on the fixed bypass, if you disconnect it wont the motor position remain in the same postion ? Does that make sense ?

Only sure way is to clamp the hose, when running there is always some air going through the stepper.
To set the base idle clamp the hose, make sure that it ticks over at 500rpm. If not, having already noted its positon so you can return it if it doesn't work , you adjust the bypass screw thingy until it does, or stalls .
One thing to note though, once you have it ticking over at 500 rpm with it clamped. Switch off, remove clamp and reset the ECU before letting it go through a learning process i.e. start it don't touch the throttle etc and let it run until the fans cut in then cut out again, switch of...presto set up and learnt new idle characteristic.
Don't be surprised if it doesn't stall sometines though as TADTS at some point . AIMHO and not necessary right, hence noting bypass screw postion before adjusting .

Harry

[brioss]

Thanks , thats my task for the weekend, although my cars too loud to leave idle on the drive