Why are there so many Stepper motors? - Defender Source
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  #1  
Old September 29th, 2014, 01:46 PM
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Stephan Laputka
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Why are there so many Stepper motors?

So last issue i'm trying to solve on my truck is the stepper motor. Engine was dying at stop lights so i ordered a new one from AB. Didn't think anything of it, threw it in the truck and now on start up it revs to 2500 RPM and stays there for 30-45 seconds. Then is it will drop to 1500. It cost me like 150 bucks or something. Figured it was a defective part. Ordered another one from Lucky 8 which cost 70 bucks and had a different part number. I compared both side by side the one from lucky 8 has shorter threads and a longer plunger. otherwise look identical. Installed the lucky 8 one and now on start up it revs to 1500 rpms and then drops to 1100 and causes slight surging when driving in the lower RPM range. These all come in a made in china box and have have gold colored plating around the part. Took the part from my brothers 94 D90, which is all black in appearance, put it in after trying these two and the truck runs perfect. Idle sits at 800, doesn't randomly rev and no surging. I went to Rovers North's site and now I see a Stepper motor for 528 bucks???! Part # RNM077. I also see another stepper motor for 169 bucks. Part #PLM077. Both are for the Defender and are different part #s from what AB and lucky 8 sent.

What's the deal? Doesn't anybody know the actual correct part # for a genuine replacement?
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  #2  
Old September 29th, 2014, 01:50 PM
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Daniel Marcello
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get one from a junkyard Astro van. Its the same part.
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  #3  
Old September 29th, 2014, 01:51 PM
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What's your vin?
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  #4  
Old September 29th, 2014, 01:54 PM
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Stephan Laputka
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Saldv3280sa980651
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Old September 29th, 2014, 02:00 PM
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ERR2263, looks NLA and aftermarket may not be available either...
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Old September 29th, 2014, 02:11 PM
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3.9 idle air control valve IAC valve stepper motor - NAPA Part # MPF21738
3.9 idle air control valve IAC valve stepper motor - AC Delco Part Number #25527077
4.0 idle Air Control Valve stepper motor - AC-151
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  #7  
Old September 29th, 2014, 02:13 PM
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Stepped motors need to adapt. It really needs to run for a good 15-30min before they settle in. Disconnect the computer to reset it. Fit the stepper motor, and then let it idle for a while. Not saying the ones you have are good, but doing this should help. Also, one off a disco 1 94-95 or 91 and up RRC should work. Usually if you clean them and the socket and have no vacuum leaks they are fine in my experience.
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Old September 29th, 2014, 02:35 PM
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Stephan Laputka
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The main reason I figured it was the wrong part or defective, was because the threads didn't seems to line up right. the IAC from the other defender has no washer, and threaded in tight and snug. These other ones had some cardboard washer with them (i tried with and without washer) and they don't thread in tight. Forget putting a wrench to it, I hand tightened it and stripped the threads closest to the base on both the lucky 8 part and AB part. As it sits now, you can un crew my stepper motor by hand since I can't take a wrench to it. The threaded body on the black stepper motor is an 1/8 inch shorter than the other two.

I have a Napa right near me, I'll try that part # and see what comes out.
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Old September 29th, 2014, 02:40 PM
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Brett Fritzler
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Quote:
Originally Posted by ini88 View Post
3.9 idle air control valve IAC valve stepper motor - NAPA Part # MPF21738
3.9 idle air control valve IAC valve stepper motor - AC Delco Part Number #25527077
4.0 idle Air Control Valve stepper motor - AC-151
Any idea why Atlantic British lists different part numbers for the stepper between D90/RRC and 94/95 D1's ?
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  #10  
Old September 29th, 2014, 02:42 PM
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Couple of other things. Check the wires on the connector, they go as bad as the steppers do. It was actually a poor connection on My old Disco 1 that was my problem. That and you need to use some carb cleaner to clean the orifice and mating surface of the plunger and in the plenum itself. The deposits are sticky and also affect its performance. On some aftermarket steppers the plug was mated 90 different.
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  #11  
Old September 29th, 2014, 03:06 PM
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As Ron said, remove power from the ECU then try again. It could take a few short trips. FWIW, I've tried two steppers before settling on a NOS Lucas stepper purchased here that was clearly used. It works perfectly.
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Old September 29th, 2014, 04:19 PM
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The stepper resets when the car is shut off. That buzzing sound is the stepper slamming in to the seat. There is no learning process for the idle
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  #13  
Old September 29th, 2014, 04:22 PM
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Stephan Laputka
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I never reset the ECU, but I have driven well over 45 mins on each one with no change.

I looked at the wires and yeah, each times the plug is in a totally different position. I've ruled out any other issues because I have one original stepper motor from another truck that when plugged in runs perfectly fine. That without re setting the ECU. What blows my mind.. is the physical dimensions of each plug is different yet each one is for a 94-95 defender 90 and cost btw. 70 and 528 bucks. Don't understand how that works.
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Old October 9th, 2014, 08:58 PM
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I tried a cross-over referenced one from NAPA $70. No go. My mechanic put in an OEM Lucas and it runs like a champ. Go figure.
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Old October 9th, 2014, 09:21 PM
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Quote:
Originally Posted by ini88 View Post
get one from a junkyard Astro van. Its the same part.
Yes...I bought a stepper motor (I think the brand is BWT?) from Pep Boys. I didn't want to blow their minds telling them it was for a D90, is stated it was for an 1986 Astro van. No problems in the last 3 years and it was $15...

Good luck...
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Old October 9th, 2014, 09:30 PM
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Jay Geaney
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Quote:
Originally Posted by Grover View Post

Yes...I bought a stepper motor (I think the brand is BWT?) from Pep Boys. I didn't want to blow their minds telling them it was for a D90, is stated it was for an 1986 Astro van. No problems in the last 3 years and it was $15...

Good luck...
Concur-
"I'd like part# AC-102."
"Okay what's it for?"
"I'd just like part# AC-102."
"Just need to see if it fits."
"Okay it's for an '86 Chevy astro."
"Okay great it fits! Here you go."
Mentally: "GFY..."
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  #17  
Old October 10th, 2014, 06:09 AM
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Originally Posted by genie90 View Post
Concur-
"I'd like part# AC-102."
"Okay what's it for?"
"I'd just like part# AC-102."
"Just need to see if it fits."
"Okay it's for an '86 Chevy astro."
"Okay great it fits! Here you go."
Mentally: "GFY..."
You nailed it!

$528 for a stepper motor is insane! My guess the part is $28 and the Land Rover box is $500...
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