Chimaera idle stepper
Discussion
Hi,
I replaced thr stepper motor last weekend as the idle would not settle down after a run at junctions etc: it would stick at about 2000rpm.
Changing the motor certainly fixed this. However, it now won't idle from cold. Even if it's sat for ten mins it needs a blip of throttle to get it to tick over upon restarting.
Please can someome just confirm -- or not -- that this is probably just the base idle that needs resetting. The adjustment screw looks well and truly seized.
I replaced thr stepper motor last weekend as the idle would not settle down after a run at junctions etc: it would stick at about 2000rpm.
Changing the motor certainly fixed this. However, it now won't idle from cold. Even if it's sat for ten mins it needs a blip of throttle to get it to tick over upon restarting.
Please can someome just confirm -- or not -- that this is probably just the base idle that needs resetting. The adjustment screw looks well and truly seized.
I did check prior to buying that the TVR one is landrover err5199. Unless the website is incorrect. They looked the same, except the Rover one looked like the shaft was stuck further out, but then I don't know what position the old one was stuck in. As I say, it works perfectly when running and warm, but only acts up when cold or warm starting. I resent paying the mark-up from TVR suppliers for parts that are from something else lol.
Every time the engine is turned off the ECU sends more than enough pulses to motor the shaft back all the way back in. The clicking you hear is the motor running out of free movement. There is no feedback to the ECU so it doesn't know if the stepper motor has moved.
I tried one of the cheap £13 ones on my last Chimaera in 2014. It would idle at over 2000 rpm when cold, bad at junctions. I had to buy a £90 'proper' one which resolved it. (Current one has canems so a different system of idle control)
It's probably one of the most frequently discussed items on here. From removing it altogether to disconnecting it after the engine is warm to leave it in a preferred position. A search will return you with hours of bedtime reading!:
https://www.pistonheads.com/search?SearchText=chim...
I tried one of the cheap £13 ones on my last Chimaera in 2014. It would idle at over 2000 rpm when cold, bad at junctions. I had to buy a £90 'proper' one which resolved it. (Current one has canems so a different system of idle control)
It's probably one of the most frequently discussed items on here. From removing it altogether to disconnecting it after the engine is warm to leave it in a preferred position. A search will return you with hours of bedtime reading!:
https://www.pistonheads.com/search?SearchText=chim...
On the subject of stepper motors I'll repeat my comments over on the shunting post.....
If you're going to manage idle using an air bleed (idle air control valve), best you make sure your wiring and earths are in perfect order, idle valves be it a Lucas stepper motor or a Bosch rotary type idle valve (as used with the Canems system) seem to be very sensitive to EMI and poor earthing, I guess because they are very low amp devices. In my opinion all vacuum leaks are bad anyway, and an idle air control valve is just a managed vacuum leak, idle air control systems need to be working 100% perfectly or you're asking for trouble.
You can see why the designers of the MBE system decided to completely do away with an idle air control valve in favor of managing idle speed using ignition timing only, if the wiring or earthing is anything other than perfect then idle air control valves can literally be more trouble than they're worth.
I still like my idle air control valve because it does a great job of increasing idle speed during the cold start warmup phase, and on the Canems system is also allows me to run an anti-stall strategy, both are excellent features that give OEM levels of driver convenience I would never be without. But in all other situations controlling idle speed with ignition timing is a way better idea than trying to do it with what is essentially a managed vacuum leak.
If you suspect your stepper motor is the cause of low speed drivability issues it's easy enough to get the car fully warm and then go for a drive with the feed hose to the stepper motor clamped off.
A clamp like this can be extremely helpful at pinpointing vacuum leaks, also pay close attention to the un-valved crankcase ventilation system on our cars as this is just another vacuum leak, all be it an essential one.... so don't clamp it off for long.
If you're going to manage idle using an air bleed (idle air control valve), best you make sure your wiring and earths are in perfect order, idle valves be it a Lucas stepper motor or a Bosch rotary type idle valve (as used with the Canems system) seem to be very sensitive to EMI and poor earthing, I guess because they are very low amp devices. In my opinion all vacuum leaks are bad anyway, and an idle air control valve is just a managed vacuum leak, idle air control systems need to be working 100% perfectly or you're asking for trouble.
You can see why the designers of the MBE system decided to completely do away with an idle air control valve in favor of managing idle speed using ignition timing only, if the wiring or earthing is anything other than perfect then idle air control valves can literally be more trouble than they're worth.
I still like my idle air control valve because it does a great job of increasing idle speed during the cold start warmup phase, and on the Canems system is also allows me to run an anti-stall strategy, both are excellent features that give OEM levels of driver convenience I would never be without. But in all other situations controlling idle speed with ignition timing is a way better idea than trying to do it with what is essentially a managed vacuum leak.
If you suspect your stepper motor is the cause of low speed drivability issues it's easy enough to get the car fully warm and then go for a drive with the feed hose to the stepper motor clamped off.
A clamp like this can be extremely helpful at pinpointing vacuum leaks, also pay close attention to the un-valved crankcase ventilation system on our cars as this is just another vacuum leak, all be it an essential one.... so don't clamp it off for long.
PhysDoc said:
QBee said:
Did you disconnect and reconnect the ECU after fitting? Not sure, but think it may need this.
I would not have thought that would have worked for the reason ianwayne said; however I tried it for nothing and it has worked!!!Thanks for the suggestion.
Edited by QBee on Friday 19th January 19:43
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