Thread: Stepper Motor - V8 D1?

Originally Posted by ariddell

Guys,
Hoping you can help for a non LR related yet strangely LR related issue this time.

My TVR has been idling like a git when cold of late. Now this is a pretty common one on Chimaeras and is usually cured by removing the stepper motor (idle speed control motor, not sure what name is commonly used for it over here) giving it a good clean and putting it back, since it tends to get gunked up pretty easily.

This used to work for mine too but i'm pretty sure now my stepper motor is failing alltogether as cleaning it no longer has any effect.

As such i'm looking to get a replacement and i think the exact same part is used on the D1 - so hoping someone can confirm. If it is the same it'd be a lot easier to get one out here than having a TVR dealer in the UK ship one out.

The arrangement on my D2 is completely different so does the attached pic look like the D1 part? If so does it require regular cleaning on the D1 too, or is this a particular TVR tendancy to get blocked up with crap?

Thanks!

Al

untitled.jpg

2-stepper.jpg

Damn, that looks irrepairable, along with the whole vehicle. Best I fly over and relieve you of this troublesome and unreliable white elephant

Al,
I would try cleaning the actual throttle body also. Around the throttle plate there is supposed to be an airgap, this, too, can be blocked with carbon etc. It will help the idle a fair bit. As regards the stepper motor, yes it looks like a RR/ D1 unit, but there is a small difference I believe with the very early hotwire 14CUX stepper motors. I THINK 1994 on were all the same, and 1991 till then were slightly different in some way because I seem to remember a part number change after the LA VIN series
Other cold idle issues with the 14CUX system are;
thermostat stuck open, coolant temp sensor fault, retarded ignition timing....again, I'll need the vehicle to repair these problems.


JC

Are you really sure the stepper needs replacing? It's quite an expensive part.

1. With the engine running pull the plug on the stepper, (does it idle better??) then turn off the engine.
2. Unscrew the stepper and then re-insert the plug (the pin should not be fully wound in as you unplugged the stepper whilst the engine was running).
3. With the stepper uncrewed into the plenum, turn the ignition on, so the lights come on (but don't start her up).

Did the pin wind itself back in?

Also check the MAF. With the engine running, pull the plug on the MAF, does the idle get worse?

Is the engine open-loop? It seems failing lambda sensors can cause the same effect.

Also, when you remove the stepper to clean it are you removing the housing from the back of the plenum too? This should be cleaned up too. It's connected with 3 x 5mm allen bolts I think.

To answer your question, that does look like the correct part, but you should get the number off the existing stepper as there are a few that look the same but have different length pins - you don't want to get it wrong!

JC - I'm still waiting for you to come to Qatar to sort my problems out!!

I replaced the stepper motor on my 96 V8 with one from a Tickford Ford.
It's a pretty common Buick part too from memory, so a Holden one will probably fit as well.

Try Triumph rover spares in SA, they used to have a TVR and are the lic serviced agents from memory.
Speak to Phil, he is most helpful

Nice wheels.

Heres one

Land Rover Discovery 3.9 idle By-pass air valve - eBay, Air Intake, Fuel Delivery, Car Parts, Accessories, Cars, Bikes, Boats. (end time 08-Sep-08 20:03:23 AEST)


Andy

Thanks guys,

It is indeed not cheap, getting quoted $315 from Land Rover and it has to come in from the UK or $95 from Triumph Rover spares. So yeah, will def keep an eye on what the one you've listed is going for Andy (presuming that's your listing as opposed to one you found due to the location ).

Will also do a bit more in the way of diagnostics on it I think as mentioned by westonben to see if i can confirm if it's definately the part at fault before replacing it. I've not been cleaning the housing so i'll give that a try to see if it improves things too.

Specific issue i've been seeing is it over reving and then bouncing the revs for a while before it eventually settles - hence leading me to think it's the pin sticking and not winding in/out properly. Start it up, it used to sit at about 12-1400rpm for the first 30 secs or so then settle down to ~8-900rpm at idle. Now it starts at 12-1400 and then gradually builds up to sit at around 2000rpm. When you pull away and first bring it back to idle at lights etc it'll bounce the rpm between about 900 and 2000 about 3-4 times before settling back up at 2000rpm, and then so long as you leave it alone for 15-20 secs will usually drop gradually back down to 8-900 and be perfectly normal from then on.

I don't think the fact that it has needed to be maneuvered into a tiny garage at the end of a laneway needing a 3-4 point turn to back it in for the last year and a half has helped either since it means always turning it off with the engine hot, and not being able to let it settle properly before taking it out after startup without asphixiating myself.

Cheers

Al

Also you need to get rid of that EA fowlcan, that is not a suitable stablemate for those thoroughbreds you have .

Originally Posted by loanrangie

Also you need to get rid of that EA fowlcan, that is not a suitable stablemate for those thoroughbreds you have .

Lol, if you'd smelt the way our dog smells after a trip to the beach you'd agree it's the perfect stablemate to the rest of the fleet!