Stepper Motor Adjustment

[keefalicious]

I have a FTO Mivec with Tiptronic gearbox.

The car would stall when starting up cold. It was as if it needed a choke. I could remedy this by putting a small amount of pressure on the throttle peddle and after a few minutes the engine would warm up and the problem was resolved - with no more issues when driving.

I thought I'd remedy the problem for good and read that the stepper motor is probably the problem. I removed the stepper and gave it a clean. I left the battery unplugged so the ECU would reset. When I put it all back together the problem was still there.

I have another FTO which has no problems with stepper (GR tiptronic version). I took the stepper from this and installed it into my Mivec . The problem is still there but now the car is constantly over revving when slow. Its quite sporadic and annoying. I'm planning on changing the stepper back again tonight but wanted to know if there's something else I should be doing. The problem is further exasperated by the fact I don't have a working rev counter to display any readings - which is making it difficult to know how much its over revving.


On another note, and hopefully not associated with the same thing, I was driving with the replaced stepper in (I pushed it a little but not more than usual) and I heard a loud pop from the engine compartment. I opened the bonnet and the battery seal had exploded out leaving some distilled water over the battery and parts of the engine. I moved the battery quite a lot whilst lifting in and out of the car and during the stepper work and thought a lose connection inside the battery cell had caused a spark which ignited the hydrogen gas inside. I checked the battery voltage and its still at 13.5V, so I cant see it having been over charging. Could this be related to the stepper. The battery is fine at the moment - despite missing the vent release plug. I think I've opened a can of worms, but cant really see how this is all related to the stepper.

Some advise from you guys would be much appreciated. I know there's other Stepper queries on this forum, but this one seems to be slightly different (because I replace the stepper).

Thanks.

[brccrx]

Maybe try to clean the throttle body, especially the stepper motor housing!

See once U remove it, theres 2 pieces that can fail, the coils (black plastic housing) and the rotor (the shaft)
so first of all get your hands on multimeter and test both coils, the one that the motor U think its faulty and the one that U think the motor is good on it.
test the resistance between all pins and compare each motor to the other.

Sometimes the coolant sensor can be the reason that the ECU doesn't set the stepper the spot it should when engine is cold.

Theres a way of checking this,
fit your old stepper motor, when engine is cold disconnect the battery like U do the ECU reset and try to start the car, if it start the stepper is fine, look for the problem elsewhere.

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