How fast should start up idle be?
Discussion
Hi All.
A request for help from the collective consciousness please...
When I start the car it catches and runs at 2500rpm for a few seconds until the stepper motor kicks in and brings it down to 900tpm or so warm and 1000 or so when cold.
Should it really flare to 2500rpm? It has a tendency frighten small animals and children and I have worries about the slumber of the residents of my local churchyard. What does yours do?
Is there a way to dial back the initial blip without causing other issues?
Cheers!
A request for help from the collective consciousness please...
When I start the car it catches and runs at 2500rpm for a few seconds until the stepper motor kicks in and brings it down to 900tpm or so warm and 1000 or so when cold.
Should it really flare to 2500rpm? It has a tendency frighten small animals and children and I have worries about the slumber of the residents of my local churchyard. What does yours do?
Is there a way to dial back the initial blip without causing other issues?
Cheers!
As usual start with simple things first.
I would suggest checking base idle setting and cleaning the stepper motor very easy to do.
I recently changed my MAF and was getting fast idle too - would come down a bit to 1000+ but when driving a low revs it was little cranky.
Standard idle should be around 850 with the air intake control governed by the ECU and stepper motor.
Base idle should be around 550 if I recall (warm engine) block the tube from the intake to the stepper motor vale and make sure there are no air leaks into the plenum or in other places.... carbon canister can tube etc.
Check base idle is at 550 or wind the idle screw until the car will hardly run this should be around 550.
For the stepper motor unclip the electrical connector, unscrew the stepper motor carefully check it is clean from carbon deposits and dirt and replace add a little bit of PTFE tape to make sure you get a good seal and do not over tighten. Plug the connector back in.
Hopefully this should help ... you can do this all in around 15 minutes - Good luck.
Update-I went through all the checks listed above. Got a new ‘Lucas’ stepper motor from eBay. Fitted it a few days ago but tonight was the first time I started the car. Revved to 1300 ish RPM then started to reduce. For £20 it was worth a try. Grin back on my face after. Nice wee drive in the sun this evening.
Gav,
This is the one. The valve sat a few mm closer to seat than the one I took out, so may help.
https://www.ebay.co.uk/itm/233848917331
This is the one. The valve sat a few mm closer to seat than the one I took out, so may help.
https://www.ebay.co.uk/itm/233848917331
Sorry for the delay in replying - I thought I would put it all together in one post!
Hi Italian Thanks for the suggestion. I had already had the base idle done at Str8six and also rechecked myself. I have already given the stepper motor a good clean too.
In fact as Mrs Spunagain reminded me it has been doing this since 1997 so I had assumed it was normal!
Looking closer it actually looks like the warm idle is closer to 1000 than 900.
I had a good poke around the engine bay and squirted lots of cracks crevices and pipe ends with brake cleaner but nothing caused the idle to stutter. I did notice that the end of the timing vacuum hose was very loose on the plenum end so I chopped 15mm off and the fit is much more snug now. Did not affect the idle though
So thanks to scottliv’s suggestion I then purchased the £22 “Lucas” stepper motor and here it is with it’s nice Logoed box!
The one on the right is the new one and you can see the closed position is not quite as retracted as my original. Both seem to be of the same sort of build standard. So I am thinking perhaps my car always had the wrong type fitted?
Anyway it has had the same effect as Scotliv’s. Revved to 1300 ish RPM on startup then started to reduce as normal down to a nice idle at 900. Taking it for a run it settles nicely as you come to a junction and it may be my imagination but it seems to be easier to put into 1st gear when idling too.
I hope it proves reliable (I will keep the old one just in case) and will report back if it fails anytime soon!
Hi Italian Thanks for the suggestion. I had already had the base idle done at Str8six and also rechecked myself. I have already given the stepper motor a good clean too.
In fact as Mrs Spunagain reminded me it has been doing this since 1997 so I had assumed it was normal!
Looking closer it actually looks like the warm idle is closer to 1000 than 900.
I had a good poke around the engine bay and squirted lots of cracks crevices and pipe ends with brake cleaner but nothing caused the idle to stutter. I did notice that the end of the timing vacuum hose was very loose on the plenum end so I chopped 15mm off and the fit is much more snug now. Did not affect the idle though
So thanks to scottliv’s suggestion I then purchased the £22 “Lucas” stepper motor and here it is with it’s nice Logoed box!
The one on the right is the new one and you can see the closed position is not quite as retracted as my original. Both seem to be of the same sort of build standard. So I am thinking perhaps my car always had the wrong type fitted?
Anyway it has had the same effect as Scotliv’s. Revved to 1300 ish RPM on startup then started to reduce as normal down to a nice idle at 900. Taking it for a run it settles nicely as you come to a junction and it may be my imagination but it seems to be easier to put into 1st gear when idling too.
I hope it proves reliable (I will keep the old one just in case) and will report back if it fails anytime soon!
I have had a little think about this and looking at the photo you can see the fibre washer is quite thick.
When I cleaned my old stepper motor, the washer had pretty much disintegrated so I replaced it with a new one from Ebay. I do wonder if I could get a similar effect by removing the fibre washer completely and just putting a bit of PTFE tape on the threads to make the seal as that would push the plunger in by a mm or so in its "open" position. However all is working well so I am going to leave it for now!
When I cleaned my old stepper motor, the washer had pretty much disintegrated so I replaced it with a new one from Ebay. I do wonder if I could get a similar effect by removing the fibre washer completely and just putting a bit of PTFE tape on the threads to make the seal as that would push the plunger in by a mm or so in its "open" position. However all is working well so I am going to leave it for now!
I believe that the stepper motor resets automatically when you switch off the ignition.
You should hear a buzzing indicating that the motor has reached its end stop position. This way the ECU has a fixed/known starting point for adjusting the correct idle position when it is started the next time.
This most likely explains the difference between your 2 steppers in the photo probably just at different positions which are then adjusted when you switch off the ignition.
I use PTFE tape and I don’t remember a washer - all works fine.
Not necessary for changing the position of the plunger as this is controlled by ECU from the closed position as noted above.
You should hear a buzzing indicating that the motor has reached its end stop position. This way the ECU has a fixed/known starting point for adjusting the correct idle position when it is started the next time.
This most likely explains the difference between your 2 steppers in the photo probably just at different positions which are then adjusted when you switch off the ignition.
I use PTFE tape and I don’t remember a washer - all works fine.
Not necessary for changing the position of the plunger as this is controlled by ECU from the closed position as noted above.
If it’s now working with new stepper leave alone but one of the problems with replacement stepper motors is the shaft and spring length is longer as can seen in the picture above.
Years ago when this subject of replacement steppers not working was often discussed one solution was to use your original plunger/ shaft in the new stepper motor thus retaining the same length.
If in its closed position it sits further out does this not mean it’s not fully sealing and shutting off air supply?
It’s a long time since I used these stepper motors but it’s worth remembering you can Unscrew your plunger from the mechanism and use it on another device.
Years ago when this subject of replacement steppers not working was often discussed one solution was to use your original plunger/ shaft in the new stepper motor thus retaining the same length.
If in its closed position it sits further out does this not mean it’s not fully sealing and shutting off air supply?
It’s a long time since I used these stepper motors but it’s worth remembering you can Unscrew your plunger from the mechanism and use it on another device.
The effect the longer shaft would be to simply to have a lower peak RPM with the stepper fully open. If you remove the stepper and just let air in in the metering hole, it will rev at about 2000 rpm which is way higher than anything ever needed, so a bit of restriction in the metering hole with a longer shaft wont matter as long as you can get the 1200 rpm or so needed for cold start and raised idle when moving. On the software front, there is quite a lot going on in the background with programmed speeds for different tunes for the base idle setting, but TBH, if you can get the base idle correct and the stepper is open 30-50% at idle on RoverGauge you are fine. What you don't want is a stepper near the end of its travel at idle. You could always add or remove washers to set its opening position at idle.
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