Stepper motor.

J L Carr · Aug 5, 2019

Hi Guys. Could someone explain what the Stepper motor is for,as mine is getting clogged a lot and it may need changing as I'm loosing power at times as I can put my foot to the floor and I get a gentle acceleration other times I get full power, I think it may be this or could it be my injectors need changing. Ideas. HELP.

marjon · Aug 5, 2019

I was always under the impression it was for idle control only.
But I suppose if it’s gummingup/clogged/sticky it might give those symptoms. But could easily be elsewhere.
Start with the cheap stuff. So cleaning it would be pretty cheap, so worth a shot. Then work from there. It’s the intermittent factor that’s the problem, so can be difficult to track.

Do you have diagnostics?

Found this may help
https://www.roverparts.com/TechTips/Base_idle_setting_procedure.cfm

Good luck.
J

J L Carr · Aug 6, 2019

Hi Marjon, thanks for that but it's for a classic 87 to 88 while my RR is a 1998, I have a great tick over no problems starting buy some times no power other times mostly when cold full power and it goes like a rocket, oh forgot to mention it's a petrol not a diesel engine. Does and body know what PSI the injectors run at, as I may just change them as they have been in the car for the 14 years of having it. Thanks.

RangeRoller dt · Aug 6, 2019

Plugs n leads okay? @kermit_rr is pretty familiar with a 4.0, bet he’d know bout the stepper

kermit_rr · Aug 7, 2019

Ha!
Do you mean the motor that bypasses the throttle body? That's the idle control, so if it was sticking open you'd have a fast idle
Your symptoms don't sound like bad injectors, or a fuelling problem. Have you checked the colour of the plugs when it's acting up?
Is the gearbox going into limp mode, ie sticking in this gear? That would give slow acceleration.
Is the throttle cable working ok?

J L Carr · Aug 8, 2019

It's not sticking in gear, gearbox not going into limp moad and throttle cable is ok, the plugs are the right colour so that's why I'm asking. Also what presure do the injectors run at I'm looking at a 20 PSI upgrade set, it just had a full service in April and it was doing this before then.

kermit_rr · Aug 11, 2019

Sorry for the show reply, I've been away
I'm not sure what the ideal pressure is but it will be in RAVE.
If you had poor fuel pressure to the injectors then it will cough and splutter then die further up the rev range as it runs out of fuel
Sounds to me like you need it plugged into diagnostics

marjon · Aug 11, 2019

J L Carr said:
Hi Marjon, thanks for that but it's for a classic 87 to 88 while my RR is a 1998

You asked about the valve. Same principle though.

J L Carr said:
what presure do the injectors run at I'm looking at a 20 PSI upgrade set,

I looked it up once when I needed to check mine (I had a big fat 0) I seem to remember finding it in rave and it was around 50 ish psi. Maybe you have a weak fuel pump. Or regulator.

J

J L Carr · Aug 11, 2019

kermit_rr said:
Sorry for the show reply, I've been away
I'm not sure what the ideal pressure is but it will be in RAVE.
If you had poor fuel pressure to the injectors then it will cough and splutter then die further up the rev range as it runs out of fuel
Sounds to me like you need it plugged into diagnostics

That's the problem, no coughing or spluttering, ticking over perfect but at times no power. I can come up a small hill where I live and my foot will be to the floor,the car will accelerate but slowly and then the next time on the same hill it will go light a bomb up it. It's just very frustrating to try and figure out what it is that's causing the problem.

Henry_b · Aug 11, 2019

That'll be a 14cu system..

The "stepper motor" is the IAC

i

kermit_rr · Aug 11, 2019

J L Carr said:
That's the problem, no coughing or spluttering, ticking over perfect but at times no power. I can come up a small hill where I live and my foot will be to the floor,the car will accelerate but slowly and then the next time on the same hill it will go light a bomb up it. It's just very frustrating to try and figure out what it is that's causing the problem.

What does the rev counter say when it's slow and when it's 'like a bomb'?
If the revs are the same then is there a blockage, ie airfilter or cat/silencer? Any chance the brakes are sticking on? Or the handbrake not releasing fully?

J L Carr · Aug 11, 2019

kermit_rr said:
What does the rev counter say when it's slow and when it's 'like a bomb'?
If the revs are the same then is there a blockage, ie airfilter or cat/silencer? Any chance the brakes are sticking on? Or the handbrake not releasing fully?

Brakes ok as well as the hand brake,it's just had a full service in April and it was the same befoe the service, as for the revs slow power low revs but at the bomb stag the revs are high.
That's why I asked about the step motor as mine was clogged up, just thought it may have been that,but I was wrong.

kermit_rr · Aug 11, 2019

Ok so it sounds like it's in a higher gear if the revs are lower and as a result you're getting slower acceleration
Either kickdown isn't working sometimes, which could be adjustment, or like i said before, it's going into limp mode, which means it's stuck in 3rd gear regardless which gear you select. Someone with more gearbox knowledge will be able to confirm I'm sure

Stepper motor.

J L Carr

Active Member

marjon

Well-Known Member

J L Carr

Active Member

RangeRoller dt

Well-Sprung Member

kermit_rr

Very

J L Carr

Active Member

kermit_rr

Very

marjon

Well-Known Member

J L Carr

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Henry_b

Think outside, no box required.

kermit_rr

Very

J L Carr

Active Member

kermit_rr

Very

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