Stepper motor - clean it or bin it

[jazzdude]

Is anyone running their Chim without a stepper motor?

I was fed up today with the fast idling that popped up again after I had reconnected my ECU after some work in the footwell, even though I had cleaned it a couple of weeks before, so I stopped and disconnected it. The car is running really smoothly and the lumpy idling reduced but I am thinking, long term, is this going to be a problem?

It took a couple of minutes to idle properly from cold without my feathering the throttle though.

Should I just buy a new stepper motor?

[Chimp871]

Jazz - besides a clean best to check it with a multimeter to check its in spec

[Discopotatoes]

also worth checking the air bypass screw is set correctly

[jazzdude]

I just took the stepper out again, thorough clean using the method that the whole plunger comes out, greased it, cleaned out the plenum thoroughly, reset the ECU and the idle has settled again but there is still that annoying high 1500rpm idle when coasting to a stop.

[blitzracing]

Download the Steve Heath Ecumate manual (google it) and read around page 35 onwards, it explains whats going on in your situation. Its unlikely to be the stepper motor itself, but an incorrect throttle pot, speed input, base idle or air leak.

[jazzdude]

Ok, Blitz, read that, good information but if I were to go through that list, would you say the base idle setting is the best place to start?

[blitzracing]

Its an easy thing to check- just clamp the air feed pipe to the stepper shut and see where the idle settles.

[jazzdude]

By 'clamp' do you mean squashing the hose with mole grips?

This sounds a lot easier than making up bungs with bits of hose and M6 bolts.

[jimed]

Just in case - when you clean the stepper you should also give the inside of the hole it screws into a good clean; think there is a small hole to one side inside the hole which you should also clean. I gave mine a good clean last week (didn't do the shaft out bit) and gave the inside of the hole a good doing with some cotton buds and also a good spray with brake cleaner (did leave it for a while afterwards to ensure it had all gone in case not good for the cats) and checked with the cotton buds after and nothing at all on it. That certainly had a good effect. The stepper was reasonably clean beforehand but after the above the tickover is better than it has been and drops straight to 900 or so so looks as if the brake cleaner might have done something useful.
Jim

[bobfather]

jazzdude said:

By 'clamp' do you mean squashing the hose with mole grips?

This sounds a lot easier than making up bungs with bits of hose and M6 bolts.

Sometimes the pipe is too stiff to clamp fully, any air passage and the base idle set-up won't be correct. Pull the pipe off near the throttle butterfly and bung both ends, easier in the long run and saves scaring the pipe

[blitzracing]

I would not use mole grips as you say, but Ive done it with a G clamp successfully.

[Chimp871]

Going back a step. Is this the first time you start or when you came to stop even when the car is warmed up?

[jazzdude]

For the first say 20 minutes of driving the tickover coming to a stop is high, say around 1500 rpm, then drops to 1200 then to 850 about 5-6 few seconds after stopping. After this 20 minutes, its coming to a stop tickover is goes down to about 1000 and then kind of settles to about 850 about 4-5 seconds after stopping.

[Pupp]

TADTS

Irritating, isn't it...

[jazzdude]

I wondered how long it would take before someone said that

[Englishman]

Pupp said:

TADTS

Oh no they don't, but a lot of people seem to put up with it. Normal behavior is close to what you experience when warm, i.e. when coming to a stop tickover goes down to about 1000rpm and then reduces further to about 850rpm after 2 or 3 seconds. Should be similar when cold.

Doesn't sound like you have much wrong though, so as blitzracing says, suggest you just work through the setup instructions as minor adjustments make all the difference.