Dodgy idling - already had new stepper
Discussion
Hi all,
Car (chim 450, 2000) recently developed an idling prob and would stall when engine was hot so garage replaced the stepper motor. Cured the hot stall problem but idling has become increasingly more erratic. Journey this morning was a nightmare!
Problem went like this: engine fire to 2k on start up and settles at 1200rpm. Pootle through estate. At roundabout dip clutch, revs soar to 1800, dip to 1k, soar to 1800 dip to 1k and so on. Carry on pootling along and car really rough below 2k. Every time clutch dipped above pattern occurs. When it gets properly warmed the flaring seems to die away a bit but idle is at 1600. Get to work, sit for ~20 secs and revs drop to 800rpm idle that i normally see.
Is there anything else that could cause it other than stepper? Also seen posts about running without stepper. Seem to suggest just taking out when engine warm - is it as simple as that? Any issues with doing so?
Any help appreciated.
Kevin
Car (chim 450, 2000) recently developed an idling prob and would stall when engine was hot so garage replaced the stepper motor. Cured the hot stall problem but idling has become increasingly more erratic. Journey this morning was a nightmare!
Problem went like this: engine fire to 2k on start up and settles at 1200rpm. Pootle through estate. At roundabout dip clutch, revs soar to 1800, dip to 1k, soar to 1800 dip to 1k and so on. Carry on pootling along and car really rough below 2k. Every time clutch dipped above pattern occurs. When it gets properly warmed the flaring seems to die away a bit but idle is at 1600. Get to work, sit for ~20 secs and revs drop to 800rpm idle that i normally see.
Is there anything else that could cause it other than stepper? Also seen posts about running without stepper. Seem to suggest just taking out when engine warm - is it as simple as that? Any issues with doing so?
Any help appreciated.
Kevin
kevinhall said:
Hi all,
Car (chim 450, 2000) recently developed an idling prob and would stall when engine was hot so garage replaced the stepper motor. Cured the hot stall problem but idling has become increasingly more erratic. Journey this morning was a nightmare!
Problem went like this: engine fire to 2k on start up and settles at 1200rpm. Pootle through estate. At roundabout dip clutch, revs soar to 1800, dip to 1k, soar to 1800 dip to 1k and so on. Carry on pootling along and car really rough below 2k. Every time clutch dipped above pattern occurs. When it gets properly warmed the flaring seems to die away a bit but idle is at 1600. Get to work, sit for ~20 secs and revs drop to 800rpm idle that i normally see.
Is there anything else that could cause it other than stepper? Also seen posts about running without stepper. Seem to suggest just taking out when engine warm - is it as simple as that? Any issues with doing so?
Any help appreciated.
Kevin
I have the same(ish) problem and the car is being looked at right now. I disconnected the stepper and it does 'cure' the problem when the car is warm it's just that it can be a bitch when the car is first turned on and is cold - trying to keep it idling until the engine warms up enough for the missing stepper to no longer be relevent - which was taking about 10 minutes.Car (chim 450, 2000) recently developed an idling prob and would stall when engine was hot so garage replaced the stepper motor. Cured the hot stall problem but idling has become increasingly more erratic. Journey this morning was a nightmare!
Problem went like this: engine fire to 2k on start up and settles at 1200rpm. Pootle through estate. At roundabout dip clutch, revs soar to 1800, dip to 1k, soar to 1800 dip to 1k and so on. Carry on pootling along and car really rough below 2k. Every time clutch dipped above pattern occurs. When it gets properly warmed the flaring seems to die away a bit but idle is at 1600. Get to work, sit for ~20 secs and revs drop to 800rpm idle that i normally see.
Is there anything else that could cause it other than stepper? Also seen posts about running without stepper. Seem to suggest just taking out when engine warm - is it as simple as that? Any issues with doing so?
Any help appreciated.
Kevin
During this time the car is prone to stall etc and you'll have to keep the revs up using the gas pedal until then. If your car is half as noisey as mine it can be embarrassing outside your door and at traffic lights etc.
The problem (I believe) might be ECU/Sensor related - but I'm not sure. I my case it's certainly not stepper related as I've had 2 or 3 other steppers tried with no difference.
Edited by im on Wednesday 22 August 08:52
Kevin,
I had exactly the same problem with my 2000 450 chim on more than one occasion.
I found that having got it warmed up for a couple of miles, if I stopped and turned it off for a few seconds it would behave normally.
The answer was to re set the stepper motor as detailed below, if that doesn't cure it clean the butterfly (a 15 minute job with a can of carb cleaner from Halfords).
One thing that Chris Baldock at James Motorsport advised me to do when my tickover was erratic was to disconnect the air intake pipe into the throttle body and clean the butterfly with carb cleaner. Also count the number of turns of the adjacent air screw to screw it right in so you can put it back to the same position, then remove it and clean it and the hole, again with carb cleaner.
Although some people will say that it's unnecessary, I was also told by Chris and Dream Machines that having disconnected the stepper motor you need to reset it.
I cannot find the procedure for this but its something like;
Disconnect stepper and switch ignition on for 10 seconds.
Reconnect and ignition on for 10 seconds
Igntion off for 10 seconds, then on for 10 seconds then start engine.
Doubtless someone will be along to confirm if this is correct and others to say it doesn't need to be done, but it worked for me, and this from two different guys that know what they are doing.
So before you start trying to do away with the stepper motor, get it working properly and it will be fine.
I've done 16K miles in two years and cleaned the stepper motor 3 times, as a result it always idles perfectly
I had exactly the same problem with my 2000 450 chim on more than one occasion.
I found that having got it warmed up for a couple of miles, if I stopped and turned it off for a few seconds it would behave normally.
The answer was to re set the stepper motor as detailed below, if that doesn't cure it clean the butterfly (a 15 minute job with a can of carb cleaner from Halfords).
One thing that Chris Baldock at James Motorsport advised me to do when my tickover was erratic was to disconnect the air intake pipe into the throttle body and clean the butterfly with carb cleaner. Also count the number of turns of the adjacent air screw to screw it right in so you can put it back to the same position, then remove it and clean it and the hole, again with carb cleaner.
Although some people will say that it's unnecessary, I was also told by Chris and Dream Machines that having disconnected the stepper motor you need to reset it.
I cannot find the procedure for this but its something like;
Disconnect stepper and switch ignition on for 10 seconds.
Reconnect and ignition on for 10 seconds
Igntion off for 10 seconds, then on for 10 seconds then start engine.
Doubtless someone will be along to confirm if this is correct and others to say it doesn't need to be done, but it worked for me, and this from two different guys that know what they are doing.
So before you start trying to do away with the stepper motor, get it working properly and it will be fine.
I've done 16K miles in two years and cleaned the stepper motor 3 times, as a result it always idles perfectly
Edited by TVR keith on Wednesday 22 August 09:34
Cheers for the responses.
im - would be interested to see what the diagnosis is with yours. i thought that if disconnecting the stepper solved the problem this meant the problem was the stepper so be intersting to see what the garage says.
Keith - When the stepper was fitted the garage at least dsiconnected the ECU and 'reset' the stepper that way. Not sure if the rest of the procedure you quote was carried out or not. Stopping and restarting with a ward engine does not solve the problem though - idle is always erratic.
I'll have a crack at cleaning the butterfly and see if that helps.
Cheers, Kevin
im - would be interested to see what the diagnosis is with yours. i thought that if disconnecting the stepper solved the problem this meant the problem was the stepper so be intersting to see what the garage says.
Keith - When the stepper was fitted the garage at least dsiconnected the ECU and 'reset' the stepper that way. Not sure if the rest of the procedure you quote was carried out or not. Stopping and restarting with a ward engine does not solve the problem though - idle is always erratic.
I'll have a crack at cleaning the butterfly and see if that helps.
Cheers, Kevin
kevinhall said:
im - would be interested to see what the diagnosis is with yours. i thought that if disconnecting the stepper solved the problem this meant the problem was the stepper so be intersting to see what the garage says.
If you swap your stepper for another known good one (and I think you already have a new stepper installed?) to try it out and the problem persists then it's either the ECU (which controls the stepper) thats at fault or one of the (many) sensors relaying incorrect/duff info back to the ECU which then incorrectly adjusts the Stepper setting based on this (duff) info.It's Mark Adams who's going to look at it so it'll get solved one way or another.
I'll let you know the outcome but it maybe a week or two before I get the car back.
Have you checked you HT leads? I've had the self same problem in the past and like you I changed the Stepper motor and it got a little better. Then I changed the HT leads and "Bingo" just fine. The problem I think is that after any misfire the lamder sencer tries to re-adjust what it thinks is a rich mixture due to the un-burnt fuel. Then next time perhaps it fires and the constant re- adjustments go on and on. The stepper and the ECU get involved and the result is rough running and wild changes in tick over. At normal speeds it's not so noticable. Although it often "shunts" a bit during gear changes.Equally I've had trouble with the metal plug caps as they can track down the inside. Remove the tin covers and "Hey Presto" no misfired and car runs fine. Hope this helps a little.
Running without a stepper has not caused me any problems apart from the first 30 seconds or so on a cold engine when you have to blip the throttle. Ive not tried it in winter however and you need to set the base idle to at least 900 rpm with the engine hot to prevent it stalling before its warm. Just block off the air feed pipe to the stepper, pictures at http://www.g33.co.uk/fuel_injection.htm . Ive tried the stepper motor reset procedure, (whilst monitoring what it does- or more to the point does not...)and I belive its COMPLETE RUBBISH. Ive emailed the author were this urban myth came from, and and had no reply to explain what its doing, but if anyone knows different please let me know. The only reset I can think of is clearing stepper motor error codes, although it is possible the ecu could work out an average stepper motor postion by trial and error untill it becomes stable- seems very unlikely however. From my experements the idle control system purely relys on pulsing the stepper every few seconds to slow the idle speed as you come to a stop, and if its wrong (too high) it send another pulse, and waits again. The problem occurs because the idle may drop faster than expected in this "wait" time, so when the next pulse is due the engine is now too slow, so it winds the stepper open again to compensate, so up go the rev's soar. The process then repeats to slow it down again. There are multiple reasons for the revs to drop too quickly, like wrong timing, air leaks, wrong base CO settings (this makes a big difference), misfires etc, and a crude system like this simply cant cope. Setting a high base idle masks the problem, as you are manually compensating for something thats already out of tolerance to allow it to tickover. Rant over.
Mark
Mark
The official range rover manual states a very simply procedure for setting the base idle. With the engine at normal running temperature plug the pipe from the stepper housing and adjust the idle speed on the plenum screw. When I did it I simply pulled the pipe off at the plenum end put a bit of thick poly bag over the spigot, then pushed the pipe back on to seal. The idle was too low when set at the "standard turns out", so raised it to idle OK. The operation of the stepper was confirmed on removal of the bag, the idle went up to around 1800, then dropped in a couple of defined steps (2-3 seconds each)back down to the mark adams setting of 1000rpm.
dwgriffith said:
The official range rover manual states a very simply procedure for setting the base idle. With the engine at normal running temperature plug the pipe from the stepper housing and adjust the idle speed on the plenum screw. When I did it I simply pulled the pipe off at the plenum end put a bit of thick poly bag over the spigot, then pushed the pipe back on to seal. The idle was too low when set at the "standard turns out", so raised it to idle OK. The operation of the stepper was confirmed on removal of the bag, the idle went up to around 1800, then dropped in a couple of defined steps (2-3 seconds each)back down to the mark adams setting of 1000rpm.
This is the problem- setting the base idle, just close off the air flow by whatever means to the stepper and adjust the screw in the throttle body it, but resetting the stepper motor itself, whats that about ? The stepper motor always winds back fully when the ignition is switched off, so allowing maximum air in when you go to start the engine next time, apart from this it will not move again untill the engine is started and is revving to high. No amount of cycling the ignition, waiting for relays to click, or disconnecting it will make it move, or "recalibrate it". Scotch mist I reckon. 
I have set my base idle to 1k(with bypass screw)and plugged stepper hose during setting,and now let the stepper do the rest it runs up to 1.5k approx cold,slowly dropping to 1k during warm up,i have no complaints with my stepper,my car is alot happier at 1k than 800rpm(car is an high cam model)but thats the cams nature,still aint gonna stop me fitting an aftermarket ECU at some point(want mapped ignition apart from other benefits)however i am convinced my car is running as good as it gets(with stock ECU)careful setting up of TPS switch and Air mass meter voltages & new genuine NTK oxy sensors have helped reach this Nirvana
Edited by That Daddy on Wednesday 22 August 23:05
blitzracing said:
The stepper motor always winds back fully when the ignition is switched off, so allowing maximum air in when you go to start the engine next time, apart from this it will not move again untill the engine is started and is revving to high. No amount of cycling the ignition, waiting for relays to click, or disconnecting it will make it move, or "recalibrate it". Scotch mist I reckon.
I thought the stepper motor cycled as soon as the ignition was switched on? Cant hear it on the LR,but damn sure the TVR has a tell-tale buzz...Dave
spend said:
So do you mean the 'whirr' when switching the ign on is it completing the reseating procedure? I was under the impression that it cycled thru its pulses at start up?
Dave
When you switch on the pump runs for a moment, when you switch off the stepper motor chunters to itself for a moment. Isn't that what happens on yours?Dave
I have come across a couple of throttles where there is mechanical play/stiction in the butterfly mechanism so that the butterfly itself does not quite return to its correct position and is held open a little. This gives higher than normal revs which the ECU tries to correct with the poor stepper motor but fails. It is worth making sure that there is no play in the butterfly spindle/throttle setup that can cause the butterfly to move open or not close correctly.
With one case, I could push the butterfly open enough with a finger to reproduce the high idle revs without the throttle or anything else moving. The play was in the butterfly spindle/return spring widget.
With one case, I could push the butterfly open enough with a finger to reproduce the high idle revs without the throttle or anything else moving. The play was in the butterfly spindle/return spring widget.
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