Problem with revs not coming up when A/C cuts in ...

[White Lightning]

Need some help please peeps ...

I have got a problem with the VR-4 where the revs at idle are not coming up when the A/C cuts in and this is causing the engine to cut out on occassion ... the fault started back about May time and was intermittent. The fault is now reproducible every time ... turn the A/C on and the revs stay at 650rpm ... sometimes dropping to 500rpm ish and sometimes cutting out.

It caused me a major problem on Wednesday night on the way home from football. It was raining hard and I was soaked from footie (rain) and the screen kept misting up so I had to use the A/C to keep it clear. I knew I had a potential issue at idle so was knocking the A/C off just before stopping at any junctions and roundabouts but ... when I came around a mini roundabout with the A/C running the car just died and I had a nice moment when I lost the power steering etc. What made it worse is the fact to restart the car I have to de-activate the immobiliser which means taking the key out of the ignition which I could not do because I was in 'D'. The result was me sat on the roundabout in busy traffic with the hazards on faffing about trying to start the thing again.

Anyway ... enough jabbering ... any ideas what the problem may be? I have done a search and found this thread:

http://www.clubvr4.com/forum/showthread.php?t=26043&highlight=aircon+revs

... looks like this was a 2.0 not a VR-4. Nick suggests a lose hose so I can try checking for that ... any ideas where to look?

Worth noting that I have not disconnected the battery in the last few months either ...

Help please ... :inquisiti

[Gly]

stepper motor.

[BraindG]

does it idle ok without aircon on? - ive had little experience with stepper motor issues, but from what ive read twill prob be first thing ppl say.. maybe..

im having problems with this aswell at the minute, so be interesting to find out

i have disconnected battery, and cleaned stepper.

[White Lightning]

Yes, it idles perfectly when the A/C is switched off. It's only a problem when the A/C is switched on.

Gly - have you come across this problem before? Will cleaning the stepper motor help or is a new one on the cards? What needs to be cleaned, if it can be cleaned?

Any chance it could be a hose to the stepper motor ? ... :thinking:

[Subaru ETA]

id say stepper motor...its all that controls your idle. when you put it to full lock do the revs come up?

[White Lightning]

id say stepper motor...its all that controls your idle. when you put it to full lock do the revs come up?

No idea ... I will check that later ... I assume they should?

[Subaru ETA]

yeah, when you put it on hard lock the p/s pump put load on the engine - just like the a/c does and the stepper motor should compensate

[BraindG]

hmmm, ill try that too then..

FYI: when i took my stepper out it was really black no matter how much i cleaned it - anyone know how much they are?

/edit nm: 85 quid - http://www.camskill.co.uk/products.php?plid=m22b0s1399p6902

[MPBVr4]

Also on eBay via "ricerocket"

http://cgi.ebay.co.uk/MITS-FTO-VR4-EVO-1-2-3-IDLE-CONTROL-VALVE-STEPPER_W0QQitemZ290150541233QQihZ019QQcategoryZ10 400QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

[White Lightning]

Popped out at lunchtime and had a try turning the wheel lock to lock, the revs definately changed when I turned the wheel. Although, it did not need to be on full lock.

Will try and check hose connections over the weekend. Could do without spending £85 on one of these at the moment ... /Grrr

[Eurospec]

That is a typical Stepper motor fault, it could possibly be the driver circuit in the ecu, but more likely the stepper.

Take it out and clean it, but i doubt that will help you, since i suspect its simply not responding to the increased load trigger.

You can get round it temporarily by adjusting the base idle (diag pin must be earthed out at the same time or connected to a logger) or by adjusting the throttle plate stop.

Hope that helps,

Cheers,

Ben.

[White Lightning]

Thanks Ben.

What's the best method for cleaning the stepper motor?

[Paul C]

sounds like stepper motor. I changed mine a few weeks ago. it didn't fail completely when it failed for me. Idling messed up and the car started to cut out when pulling away from idle.

[BraindG]

i used a cloth - didnt work very well though, was a bit scared to attack it with a blade... but i did :) - it didnt help get the blackness off though, seemed more like melted plastic than muck.

[Paul C]

Thanks Ben.

What's the best method for cleaning the stepper motor?

dont know if this is best advice but spray brake cleaner.

[psbarham]

dont know if this is best advice but spray brake cleaner.
yeh brake cleaner will work a treat , and it won't disolve the stepper motor either, and if that doesn't work you can sniff the brake cleaner and then you won't care about the poor idling for 20 mins :thinking:

[bradc]

Well, sounds like everyone has solved it, in the mean time you can try coming to a stop using your left foot for braking and your right foot for keeping the revs up a bit. you only need to go up to about 1000rpm or so and it will keep the car running.

[Subaru ETA]

i have at work the pins to check the resistance across..if i remember correctly the middle 2 pins are the earths and you check resistance between them and the others but cant remember which pins to test between ...if you dont fix it before monday ill post which pins after work

[david]

i have the same problem but have noticed when the engine is cold turning the a/c on will bring the revs upabove the cold start.

[White Lightning]

Have not really had chance to look too closely at this yet. I did manage to at least pop the bonnet this weekend to check the fluids (I've been so busy in the garden!) and I located the stepper motor. Noticed that there was one small hose that had come slightly loose. So, I tightened that up but I don't think it was loose enough to cause a problem.

One thing I have found is that the fault is not permanent yet. The fault seems to only really happen when the engine is hot. Therefore, on my drive to/from work, when oil temp only gets up to about 70oC there is no problem and the revs still come up with the A/C. It's only after a longer trip (or a lap of the Ring!) that I seem to get a problem.

Will keep the thread updated as I learn more ...

[Eurospec]

Thanks Ben.

What's the best method for cleaning the stepper motor?

Okay so this is from memory since i dont have one here to look at!

Remove from the car and as a few people have suggested, clean it up with brake cleaner. Use the brake cleaner/colth combo, but be sure not to leave any lint stuck on it.

If the nose is very heavily crusted, a LITTLE scrapage with a knife like barry did is fine. Just try not to damage it.

Then remove the three screws and open the little sucker up.

You will find the coil, a little spring, a nice bearing with a spindle, and then a kind of caged bit. Remove all the components slowly and note where they all live. Clean all of it up using your brake cleaner cloth combo. Feel the little bearing to see if its toasted or not (often are) but you will be surprised that giving the innards a good clean very often does help it.

Personally i dont spray the coil bit, i think that might short it.

When you re-assemble the tip protrusion should be between 19 and 21mm (That might be FTO though, so check!) and you can adjust it by turning the little spindle with the nose section assembled.

Hope that helps,

Cheers,

Ben.

[ANTHONY]

so will cleaning solve the problem or is it just a short term fix? and is it better to replace the motor

[stuartturbo]

to check assuming they are the same check resistance
pin1-2
pin2-3
pin4-5
pin5-6 should be about 30 ohms
good clean is a temp but may need coils replacing

[White Lightning]

Now that the temperatures have increased here in the UK this problem has started to rear it's ugly head again ... I guess I should get my finger out and try the clean that Ben suggested this time /pan

[White Lightning]

Armed with a spare stepper motor from PT I decided to remove mine today and strip it down. I found that the tip of my stepper was very black and cacked up. I cleaned it up using some Wynn's fuel injection intake and carb cleaner that I had lying around from years ago and it seemed to clean up OK. I also stripped it down as Ben suggested and gave it a clean inside.

At this stage, I compared it to the spare and found that they were actually very different designs. Ultimately, they fit the same but mine had a brown casing on the back and three screws holding the two bits together and the spare one had a black casing with two screws. The designs inside, although fundamentally the same were also very different. Perhaps one is a newer/better design?

Because of this, and the fact the the bearing on mine felt as good as new (whereas the other one didn't feel to good) I decided to refit the original one having given it a good clean.

Put everything back together and let the car warm up and idle, and it was happily increasing/decreasing the revs as the aircon cut in and out. So, I took it for a blast to see if it had made any difference ... aircon set to ice cold!

Well, the car didn't cut out once but on one roundabout the revs dropped below 500rpm again ... so I suspect I haven't fixed the problem. Also, the ambient temperatures aren't that high today so I can't really call it a comparitive test!

Will let things be this week and see if clean has made any difference whatsoever!

Anyway ... thanks for listening to my little story for the day :rolleyes3

[bradc]

Did you see Kitty's post about the ecu plugs and that one wire that lets the ECU know that the AC is on?

[Turbo_Steve]

or indeed (and possibly more significantly) the AC load signal on the TCU.

Also, there are a couple of pressure pipes connected to the aircon system that maybe be significant / leaking.

I am experiencing the EXACT same problem as you. I didn't have it until I changed the sparkplugs, so I am absolutely convinced that I have disturbed something: it's too much of a co-incidence.

The other thing that I reckon is significant is that on mine I get "Skiddy Car"..if you see it, and get on the throttle (or off the brake) basically let the engine work less hard, it'll catch it, the light goes off and it doesn't stall.

So the question is: what does the skiddy car mean? I suspect it's trying to tell me there isn't enough vacuum.