V6 Idle air control valve - stepper motor query.

Hello,

I'm still working on my V6... trying to get it ready after an MOT fail.

The latest problem that I've found appears to be with the idle air control valve.

Symptoms are: Slight delay in the return to idle time after "blipping" the throttle... , occasional raised tickover...This happens about 3 times in 4 so I suspected (and was guided to by Nodge68) a sticky valve.

The valve housing was as gummy as heck.. cleaned it out with carb cleaner.. but with little improvement.

I now think that the stepper motor (which actually operates the valve, under computer control) is contaminated with oil. It works.. i.e. moves in and out but appears "sluggish".

Does anyone know if it is possible to just buy the stepper motor part?
If yes or no... any idea what the part number is for a 2001 V6?? I've had a quick look at a few LR spares websites.. most only give part numbers with no confirmation of even what model land rover they are for.

I've seen similar ones on Ebay... They appear to be a relatively standard part, given that some have different valve "ends".

Has anybody found an equivalent as I expect a LR part to be expensive.

Bodge99.

Try WD40 as it lubricates as it cleans
I've never seen or heard of the actual stepper failing. Often it's just a build up of sludge that contaminates the valve. If it really is shot then I'd pick up a used complete TB off eBay, they come up pretty often at low prices too.

Hello.

Nodge68:

Thanks for that... I'm the sad sort of *** that thinks about these things in the middle of the night... so I got up, removed the stepper motor part from the housing and "had a play".

I'm also "into" vintage electronic repair (esp. valve radio, electromechanical calculating machines and '70s calculators... very sad, I know...)

I'm aware of the advantages of WD40... I'm also aware of the problems that it can cause in small electromechanical devices. As you say, it will free stiff mechanisms but over time it can cause problems in such things as stepper motors. Yep... OK.. probably not as bad as engine oil contamination but there are other options...

I've found that after cleaning a small electromechanical assembly that silicon oil works wonders.. (e.g. It's perfect for lubricating the bearings in computer cooling fans).
The problem accessing a (relatively) sealed device such as the stepper in the valve assembly is that a lot of possible candidates for cleaning carry significant risks to the electronics inside...

Things like petrol or carb cleaner can attack the insulation on the stepper motor pole windings... The deposits left by WD40 can combine with other crud (old grease etc.) and "thicken up" over a relatively short time.

What I've tried is this (nothing to lose really...). Half filled a jam jar with plusgas, place motor in jar and leave for an hour.. remove motor and leave to drain for an hour. I also blew out as much as possible with compressed air. I then sprayed 1/4 of a can of silicon oil into it...I then left the motor to drain overnight.

The motor mechanism now seems to be much smoother. I haven't tried it powered on the car yet, (things to do for SWMBO) but it steps smoothly on the bench.

A bit of a bodge.. but I don't want to destructively dismantle it until I have a spare.

If I do manage to get a spare, I'll open up the old one and post a writeup here on overhauling it...

Thanks very much for your help.. much appreciated!

BTW, I had an off forum email from somebody here about my nickname.. asking if I was "having a pop" at yours... I'm not.. I've used this nickname online for several years.. You'll see it on several electronics and fishkeeping forums.

I'll update with progress...

Bodge99.

Minor update...

Following Nodge68's advice, I've been ordered by SWMBO to buy a S/H throttle body off of ebay.. She got sick of me "humming and harring" whilst looking at the cheapest complete one...

At least I've now got a spare... I'll add the "Idle Air Control Valve Stepper Motor Repair and Overhaul" project to the "getroundtoit" list, assuming that the replacement works...

Would anyone be interested in me posting a simple to build test circuit for this one??
It would have to wait until I've opened the existing one...

More later..

Bodge99

get a metal throttle body - not plastic.

The Mad Hat Man:

Yep... have done so.. thanks.

Bodge99

Hello,

I refitted the (cleaned) idle control stepper and valve housing this morning.
On starting, the engine went to just under 2000 RPM on tickover. Revving it gave a smooth return to this RPM.. not quite right yet..

Then I remembered that the control unit stores the last used idle stepping position in memory (I think that it's volatile memory.. not sure..).

Disconnecting the battery for a few minutes allows a "real" power off and forces a reset however the previous positions are stored.. I did this.
On restarting, I was pleased to see a normal tickover. Idle return after revving the engine is fairly quick and very smooth.

I'll view this one as "fixed" and see what happens.

Bodge99.

Hello.

Just for info.. The complete IACV (housing and stepper unit) is described on the parts catalogues as "Valve assembly-fast idle TBi" part number MLV100160L.

Price is a cool £130.. The gasket, O-ring and 4 fixing screws are an extra £9.20. (MKG100260L)

I will look at writing up a stripdown and overhaul for the stepper part..

BTW, The S/H throttle body that I bought on Ebay arrived this morning. It's complete and is actually cleaner then mine...

Bodge99.

The Mad Hat Man said:

get a metal throttle body - not plastic.

Click to expand...

KV6 only had a metal TB

Hello,

I read somewhere that there is a plastic substitute that some of the MG boys used.. unsure from what it came from originally though.

Bodge99

bodge99 said:

Hello,

I read somewhere that there is a plastic substitute that some of the MG boys used.. unsure from what it came from originally though.

Bodge99

Click to expand...

Only on the 1.8 K series. Only that the VVC TB and that fitted to the early 1.8 was alloy. Most fit the VVC version as it's larger. The KV6 always had the alloy 70mm TB.

That will be the one...

Bodge99