Idle problems

[jimmyV8]

After a spell of fast idling I decided to sort it out and cleaned the stepper motor and reset the idle screw as per the Heath bible. After setting the idle screw 2 and half turns and clamping the air bypass pipe the car wouldnt run? I removed the clamp and started it up and it ran fine, at which point i then attempted to clamp the pipe and the engine just cut out. The idle is better already but just wanted to set it up correctly but having trouble setting up the base idle? Any suggestions? Cheers.

[dwgriffith]

Wind the screw out until when you clamp the pipe the idle speed is at the base setting.

[jimmyV8]

Thanks for a quick reply, the problem is that the car wont run at all when the pipe is clamped. Do u mean that the idle screw needs to be wound out more than 2 and half turns and then clamp the pipe, and back it off afterwards?

[dwgriffith]

The stepper motor can only control the idle speed over a narrow(ish) range. The 2.5 turns on the plenum bypass screw is the start point which many engines work fine with, maybe yours needs a bit more? Screw it out another turn then see if it will still idle when you clamp the pipe to the stepper, if not screw it out a bit more until it will. Once it will idle with the clamp on you can then use the screw to set the idle rev's at the speed you want. Don't make the mistake I made once using a piece of plastic bag to plug the pipe on the plenum, when I removed the pipe I didn't hold the plastic and it instantly got sucked down the pipe. Luckily it stopped in the stepper housing rather then getting into the intake. The engine needs to be up to full working temp when setting it up?

[jimmyV8]

Thanks for your help, I think that may have been some of the problem as the car wasnt totally warm. Will give it a go.

[GreenV8S]

jimmyV8 said:

After a spell of fast idling I decided to sort it out and cleaned the stepper motor and reset the idle screw as per the Heath bible. After setting the idle screw 2 and half turns and clamping the air bypass pipe the car wouldnt run? I removed the clamp and started it up and it ran fine, at which point i then attempted to clamp the pipe and the engine just cut out. The idle is better already but just wanted to set it up correctly but having trouble setting up the base idle? Any suggestions? Cheers.

Rather than clamp the bypass and then try to run the car, get the car warmed up and idling and then squash the bypass with your hand. This is easy to do by pushing it against the throttle assembly. The more you squash it the lower the revs will get. With it completely squashed the engine should idle at about 500 rpm. It's touch and go whether the engine will actually idle that low, it should if it's in a good state of tune but some won't. If the engine seems to be stalling, easy off the pressure on the hose to bring the revs up a little to catch it before it completely stalls.