Idle stuck at over 1200 rpm when hot - leak?
Discussion
Before you say 'stepper motor clean' I did just that, took it to bits so cleaned the shaft and spring too, and used a dozen qtips and cleaned out the hole in the plenum - which indeed came out black.
Reset the ECU and let the car go through 3 fan cycles for good measure and although it was initially idling lumpily, it settled down to a smooth 850 - 900 rpm. Started it this morning, after an initial high idle period for a minute, the idle settled down in 3 stages to 850 rpm, then I set off.
On the move, once the car was coming up to temp (ie fans cutting in and out) at junctions or stopping, the idle would not come down below 1200rpm. Turned it off to bring in the stepper motor, start it, the same.
Does this sound like a leak that opens up when hot, and if so, where do I check?
Reset the ECU and let the car go through 3 fan cycles for good measure and although it was initially idling lumpily, it settled down to a smooth 850 - 900 rpm. Started it this morning, after an initial high idle period for a minute, the idle settled down in 3 stages to 850 rpm, then I set off.
On the move, once the car was coming up to temp (ie fans cutting in and out) at junctions or stopping, the idle would not come down below 1200rpm. Turned it off to bring in the stepper motor, start it, the same.
Does this sound like a leak that opens up when hot, and if so, where do I check?
Or your stepper motor is sticking when the electrical pulses are trying to move it.
If you have a good idle then bad then good I'd not suspect a leak so much
With the suitable diagnostics you can remove the stepper and operate it manually, that's how I come to see this problem with mine. It would jerk out in very small movements, you can feel the pulsing through your hand and sure enough mine would start out ok then faulted to move although the pulse could be felt.
I found by letting the stepper motor cool down when off the engine, reset ecu and it would work perfect until it got hot again.
Just symptoms to keep in your mind set
If you have a good idle then bad then good I'd not suspect a leak so much
With the suitable diagnostics you can remove the stepper and operate it manually, that's how I come to see this problem with mine. It would jerk out in very small movements, you can feel the pulsing through your hand and sure enough mine would start out ok then faulted to move although the pulse could be felt.
I found by letting the stepper motor cool down when off the engine, reset ecu and it would work perfect until it got hot again.
Just symptoms to keep in your mind set
Check your base idle too. Quick check by clamping the tube that allows air to the stepper motor body. You can clamp it temporarily by nipping it with mole grips then twist it to ensue its completely sealed off, or use proper tube clamp pliers if you have them. The revs should drop to 500 ish. If they don't then your base idle needs adjusting or you do indeed have an air leak in plenum area.
PS When I wanted to check mine out on the road I used the two halves of a disassembled clothes peg nipped on the tube with mole grips. My revs dropped right down to 500 confirming my Air Idle Valve working as it should when release it idles bob on at 900 rpm
PS When I wanted to check mine out on the road I used the two halves of a disassembled clothes peg nipped on the tube with mole grips. My revs dropped right down to 500 confirming my Air Idle Valve working as it should when release it idles bob on at 900 rpm
I'm on green tune so have manually set the base idle and the AFM in the past so know how to do that 
I also suspect that the stepper motor is not working properly once the engine heats up, literally once I get to the top of the road it idles fast, after it was idling perfectly on my drive.
I also suspect that the stepper motor is not working properly once the engine heats up, literally once I get to the top of the road it idles fast, after it was idling perfectly on my drive.
I had the opposite problem a couple of years ago. Engine idled fine when cool/cold, but as soon as it got hot it simply would not hold an idle at all.
Very embarrassing at roundabouts etc.
I had just been to see Mark Adams to have the 14 CUX remapped, but even he couldn't work out why my car wouldn't idle, and left me with the issue.
I tried unplugging the stepper, cleaning it, resetting the base idle, nothing stopped it.
My throttle pot had already been set by Mark, and I was running out of ideas when I called Rob at V8D, purely for information on the injectors he had installed recently. Straw grasping was my specialist subject on Mastermind.
Now he is a friendly guy and was keen to help, and suggested I get the car over to him there and then.
He is only about 30 miles from me, so i went. Car stalled at every junction on the way.
On arrival he did all the things you would expect, checked the idle, fuel pressure, re-set the throttle pot, checked the stepper, nothing would solve it.
Then I heard him say to himself "it must be the stepper", so I asked him if he had an old one in his old engine bits store.
Sure enough he did have, fitted it, never had the problem from that day to this.
So what i am saying is you may need to replace the stepper rather than clean it, but whatever you do, get one from a reputable source, as the cheap Chinese copies on Ebay are rubbish.
Very embarrassing at roundabouts etc.
I had just been to see Mark Adams to have the 14 CUX remapped, but even he couldn't work out why my car wouldn't idle, and left me with the issue.
I tried unplugging the stepper, cleaning it, resetting the base idle, nothing stopped it.
My throttle pot had already been set by Mark, and I was running out of ideas when I called Rob at V8D, purely for information on the injectors he had installed recently. Straw grasping was my specialist subject on Mastermind.
Now he is a friendly guy and was keen to help, and suggested I get the car over to him there and then.
He is only about 30 miles from me, so i went. Car stalled at every junction on the way.
On arrival he did all the things you would expect, checked the idle, fuel pressure, re-set the throttle pot, checked the stepper, nothing would solve it.
Then I heard him say to himself "it must be the stepper", so I asked him if he had an old one in his old engine bits store.
Sure enough he did have, fitted it, never had the problem from that day to this.
So what i am saying is you may need to replace the stepper rather than clean it, but whatever you do, get one from a reputable source, as the cheap Chinese copies on Ebay are rubbish.
I think you are right.
The other day, after idling fine for about 20 mins, it started cutting out at every traffic light stop. When stopping, the revs would drop down to something quite low, try to correct to say 1200rpm, then stall.
Tvr Parts, Powers etc all reliable places for a replacement or do I try the Land Rover parts sites that are often cheaper?
The other day, after idling fine for about 20 mins, it started cutting out at every traffic light stop. When stopping, the revs would drop down to something quite low, try to correct to say 1200rpm, then stall.
Tvr Parts, Powers etc all reliable places for a replacement or do I try the Land Rover parts sites that are often cheaper?
Englishman said:
Yes, stepper motors can have a mind of their own.
Is your car still idling at 1200rpm after a period of time or does it settle to where it should be after >5 seconds stationary?
Up until recently it did come down after a few seconds which I understand is normal but now it stays up at 1200.Is your car still idling at 1200rpm after a period of time or does it settle to where it should be after >5 seconds stationary?
jazzdude said:
I think you are right.
The other day, after idling fine for about 20 mins, it started cutting out at every traffic light stop. When stopping, the revs would drop down to something quite low, try to correct to say 1200rpm, then stall.
Tvr Parts, Powers etc all reliable places for a replacement or do I try the Land Rover parts sites that are often cheaper?
I find Rimmers in a Lincoln good for Rover parts. Call them and ask the provenance of the parts you want. Or start a thread on here or on TVR sell and buy in Faceache asking if anyone has a genuine old one available.The other day, after idling fine for about 20 mins, it started cutting out at every traffic light stop. When stopping, the revs would drop down to something quite low, try to correct to say 1200rpm, then stall.
Tvr Parts, Powers etc all reliable places for a replacement or do I try the Land Rover parts sites that are often cheaper?
Other things to look for the idle will remain high if the ECU thinks either the throttle pot is not fully closed, or if there is a speed input from the speedo box when the car is stationary- but you are far better off with diagnostics to see what mode the ECU is in (ie idle or not) and if the stepper can be made to move reliably.
Yes, Rovergauge should help you diagnose the issue.
If you do need standard Rover parts, there is no reason not to use a dealer or reputable third-party supplier to avoid the TVR tax. I have several times without issues. The last time I used this company: https://www.lrdirect.com/ but not for a stepper motor.
Good luck with the diagnosis!
If you do need standard Rover parts, there is no reason not to use a dealer or reputable third-party supplier to avoid the TVR tax. I have several times without issues. The last time I used this company: https://www.lrdirect.com/ but not for a stepper motor.
Good luck with the diagnosis!
Remove the stepper then plug it back into the wiring.
With the stepper in your hand you can us RG to drive it in and out. you should be able to see and feel if it is working smoothly.
You can also drive it out until the inners and spring fall out. With it in bits you can do a much better job of cleaning it. When it is clean grease it a little with Vaseline and hold the bits in place then drive it in using RG.
Steve
With the stepper in your hand you can us RG to drive it in and out. you should be able to see and feel if it is working smoothly.
You can also drive it out until the inners and spring fall out. With it in bits you can do a much better job of cleaning it. When it is clean grease it a little with Vaseline and hold the bits in place then drive it in using RG.
Steve
The plot thickens.
Took the car out this morning for an early morning drive. This time the opposite to yesterday, the idle at startup now stayed at 1500 rpm, would not come down even though I left it there for a few minutes. Out on the road, for the first 20 mins, the idle stayed at around 1200 rpm each time I stopped.
Turned the car off for 5 minutes to pop into shop, started it, still warm, and the idle reduced perfectly to 850 rpm after a few seconds and a couple of staged drops. Thought this was a fluke and it was as for the next 10 minutes the idle stayed high again at 1200 rpm. For the last few miles before getting home though, it started working normally at each stop and in my drive at home, again, idled back down to 850 rpm before I turned it off.
Yesterday, I did a full 100-mile round trip so 'ECU must be learning' ideas don't seem to be the case.
So what the hell is going on with this thing? I can go online tomorrow and buy a new stepper but the one on there is obviously capable of working properly so how do I get to see what it is actually doing?
Took the car out this morning for an early morning drive. This time the opposite to yesterday, the idle at startup now stayed at 1500 rpm, would not come down even though I left it there for a few minutes. Out on the road, for the first 20 mins, the idle stayed at around 1200 rpm each time I stopped.
Turned the car off for 5 minutes to pop into shop, started it, still warm, and the idle reduced perfectly to 850 rpm after a few seconds and a couple of staged drops. Thought this was a fluke and it was as for the next 10 minutes the idle stayed high again at 1200 rpm. For the last few miles before getting home though, it started working normally at each stop and in my drive at home, again, idled back down to 850 rpm before I turned it off.
Yesterday, I did a full 100-mile round trip so 'ECU must be learning' ideas don't seem to be the case.
So what the hell is going on with this thing? I can go online tomorrow and buy a new stepper but the one on there is obviously capable of working properly so how do I get to see what it is actually doing?
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