Stepper motor. Again.

[ianwayne]

My idle speed has been all over the place from cold for ages, but OK once warm. Shunting, idling at 2k rpm at junctions before slowly falling back, embarrassing at petrol stations too.

Anyway, turns out I had a Chinese one fitted, as suspected. A thread on here from last year suggested the copy ones have the cone too far out - http://www.pistonheads.com/gassing/topic.asp?t=134...

However, I have discovered the opposite. Below is a photo of the copy one on the left, the genuine one on the right:



You can see the cones are actually slightly different shapes too. What a transformation. Starts and idles at 1k straight away, no 'thinking about it' for a while. No shunting. Idle speed drops off quickly on throttle lift. Dipping the clutch whilst going along previously would send the idle speed to 2k!

Bit the bullet and paid £93 at Racetech inc P+P. I ummed and aaahed at various options but glad I went for the genuine item.

[SwanJack]

I bought an ebay £17 item ans cut the shaft down as metioned in another thread. Works perfectly.

[SwanJack]

I bought an ebay £17 item ans cut the shaft down as metioned in another thread. Works perfectly.

[SwanJack]

I bought an ebay £17 item ans cut the shaft down as metioned in another thread. Works perfectly.

[pincher]

SwanJack said:

I bought an ebay £17 item ans cut the shaft down as metioned in another thread. Works perfectly.

SwanJack said:

I bought an ebay £17 item ans cut the shaft down as metioned in another thread. Works perfectly.

SwanJack said:

I bought an ebay £17 item ans cut the shaft down as metioned in another thread. Works perfectly.

Can I buy one of your spares?

[MADMAX2]

I've got a brand new one without a shaft ( long story. Don't ask!!!!) so you can put your old one in bought it from TVR power then a few months later Racetech had a 50% off sale off the original OEM ones so I bought that


So if anyone wants it and got beer tokens they can

[ianwayne]

SwanJack said:

I bought an ebay £17 item ans cut the shaft down as metioned in another thread. Works perfectly.

My point with the photo was that the copy one already had a shaft that was actually shorter than the genuine one.

Also, the initial shaft length may not be that important. My idling was all over the place because the copy one obviously responded too slowly to ECU inputs. By the time the shaft moved, the ECU had told it to move the other way and so on. I would sit at a junction about 2 mins after setting off, and the idle would be oscillating between 1000 and 2000 rpm! Some people have been lucky to have cheap copy ones work it seems, mine didn't.

[SwanJack]

ianwayne said:

My point with the photo was that the copy one already had a shaft that was actually shorter than the genuine one..

I guess it depends on whether or not they are both fully retracted.

[ianwayne]

The copy one was removed after the engine had been stopped and the ignition turned off. This retracts the plunger as far back as it will go. The new one was as it came out of the box.

Went 30 miles in the car yesterday to get it properly warm and it behaved impeccably. I put up with hunting and shunting for 6 months longer than necessary; I think I was in denial of having a cheap 'chinese' stepper motor fitted. I'd looked up throttle potentiometer problems, ECU spurious inputs and so on. In my case, it really WAS the stepper motor, although I realise it's not the case for everybody's idle problems.

Edited by ianwayne on Monday 25th August 18:35

[SwanJack]

IIRC out of the box they are not retracted.

[ianwayne]

I removed it after running the car to check:



Granted, it is now slightly further retracted than when it came out of the box, but all my research on here (on various threads, not just the one referred to previously) had led me to believe that the poor quality copy ones had shafts that were longer, but the reverse has been my experience.

The genuine one that has my car running fine has a shaft that doesn't retract as far as the copy one previously fitted.

[RDJ]

I've discovered the sealing washer on the cheap ones to be their weak spot. They are made of cardboard and tear when compressed leaving a small gap that lets air in. Bit of silicone smeared around the join does the trick.

[ianwayne]

I think I read on here that air doesn't really get past the threads until it's almost all the way out. I started the car with the stepper motor loose in the threads and it made no difference. I put PTFE tape on it to make it a tighter fit so it doesn't come loose on its own with vibration. Having a 32mm socket helped too.

[RDJ]

Might have been coincidence in my case but when I sealed around the gasket it ran better

[hififreak]

i had to Change idle air valve this year, ordered one in the UK....buuuuut got the wrong one...my fault!

going 30 miles in the City in 3rd gear means you can lift your foot don't touching gas pedal and Holding Speed....grrrr++++

i measured everything....fully retracted same length, same cone....but it was not ok!

so i put off the cone which is glued on a thread...then i glued in on again with 2mm more length fully retracted....aaaaand it works!!!

why it was idling wrong----i do not know!

it is PWM with 4 Pins that are changed that way

---+
--+-
-+--
+---

so normally same length means same stepping....but maybe the ERR5199 has a stronger mini-stepper-motor inside