High Idle Speed when drivng

[911motorsport]

Grrrrrrrrr! (rrr)

Car starts great and settles to a nice 900RPM tickover. However......... When I start driving the RPM then settles at 2000 RPM. If I stay perfectly still (the car) for about half a minute the revs
e v e n t u a l y settle back to 900RPM. Repeat ad-nauseum. What is causing this????? (please)

4.3BV, Mark Adams Tornado Chip, 218 Cam.

[pwd95]

Sticky stepper?

[pwd95]

Ere iw go

http://www.tvrcc-south-wales.co.uk/stepper.asp

[911motorsport]

pwd95 said:

Ere iw go

http://www.tvrcc-south-wales.co.uk/stepper.asp

Thanks PW but I don't think its the stepper I'm afraid. I removed it and stripped it down / cleaned it / lubricated it, earlier this evening.

I unplugged it and ran the engine and it settled at 2.5k revs. What does that tell me?

[pwd95]

Uuurrrm... too much air getting in somewhere?

[pwd95]

Or faulty stepper, not closing properly?

[GreenV8S]

911motorsport said:

I unplugged it and ran the engine and it settled at 2.5k revs. What does that tell me?

At the moment you disconnected it, was the engine warmed up and idling steadily at the normal idle speed?

[paulathome]

Have you recently had a flat battery, or disconnected the battery for any reason?
Might be worth disconnecting the battery for 10 seconds and then reconnect smartly, this will reset the ECU. Mine has had a similar tick over problem and resetting the ECU has cured it.
If you want to run the car without the stepper motor you need to disconnect it when the engine is up to temperature and running at a normal tick over, then disconnect WHILE the engine is running.
If you switch off the ignition the stepper motor will park itself so loosing the correct position in the air bypass aperture.
You will find however that you will need to give it a bit of throttle when cold to keep it from stalling.
Hope this helps.
Paul.

[911motorsport]

GreenV8S said:

911motorsport said:

I unplugged it and ran the engine and it settled at 2.5k revs. What does that tell me?

At the moment you disconnected it, was the engine warmed up and idling steadily at the normal idle speed?

Yes. Engine was warmed up and idling nicely at 900rpm. I then turned engine off, diconnected stepper, and re-started engine. 2500rpm!

[911motorsport]

paulathome said:

Have you recently had a flat battery, or disconnected the battery for any reason?
Might be worth disconnecting the battery for 10 seconds and then reconnect smartly, this will reset the ECU. Mine has had a similar tick over problem and resetting the ECU has cured it.
If you want to run the car without the stepper motor you need to disconnect it when the engine is up to temperature and running at a normal tick over, then disconnect WHILE the engine is running.
If you switch off the ignition the stepper motor will park itself so loosing the correct position in the air bypass aperture.
You will find however that you will need to give it a bit of throttle when cold to keep it from stalling.
Hope this helps.
Paul.

Aaah! See my reply above

Edited to add: I unplugged the ECU for a couple of minutes last night to see if this would cure the problem (It didn't).

Edited by 911motorsport on Wednesday 16th January 22:52

Edited by 911motorsport on Wednesday 16th January 22:57

[V8 Animal]

Had exactly the same problem.
Replace stepper motor im afraid.

[GreenV8S]

911motorsport said:

Yes. Engine was warmed up and idling nicely at 900rpm. I then turned engine off, diconnected stepper, and re-started engine. 2500rpm!

You need to disconnect it WHILE the engine is idling steadily at the right speed.

[im]

GreenV8S said:

911motorsport said:

Yes. Engine was warmed up and idling nicely at 900rpm. I then turned engine off, diconnected stepper, and re-started engine. 2500rpm!

You need to disconnect it WHILE the engine is idling steadily at the right speed.

Correct.

[TVR keith]

Perhaps your stepper motor needs resetting. I have copied the below from a previous post of mine. A number of people have said that this is not needed but all I can say is that it fixed the problem for me. Costs nothing, takes 1/2 an hour

I cleaned the stepper motor and the idle was then wrong. It would slow to about 1200 rpm, then speed up briefly to about 1600rpm then slowly drop to about 800rpm where it would remain.
I originally asked Dream Machines and was told that if the stepper motor has been disconnected it must be set up again. I did as instructed and all was well, stupidly forgot to write the procedure down.
Recently went through the same procedure again and asked Chris Baldock at James Motor Sports (he is ex workshop manager for Walldonway ex TVR main dealer).
When told the procedure I remembered it from before to be the same so I'm thinking it must be right.
Procedure is;
With engine at operating temparature,
Disconnect stepper.
Ignition on for 10 secs (do not start engine).
Connect stepper.
Ignition on for 10 secs (do not start engine).
Ignition off for 10 secs.
Restart engine.

Interestingly Chris Baldock also told me that it is best to clean the throttle pot with carb cleaner at the same time;
Remove the pipe that links the Stepper motor to the throttle pot and clean it out,
Remove the pipe that connects the air flow meter to the throttle pot.
Screw the base idle screw right in, recording the number of turns. Then remove it.
Clean the hole that it sits in and also the butterfly and neck around it using a bit of rag to soak it up so not much goes into the engine.(Mine had a fair bit of gunge here)
Reassemble making sure the idle screw is wound right down and then out by the number of recorded turns.
It sounds a lot but only took about 1/2 hour and now idles perfectly

[spend]

Mmmmmmm... Stepper Folklore

I think Matron was right "just take an asparin, it will go away"

Dave

[911motorsport]

TVR keith said:

Perhaps your stepper motor needs resetting. I have copied the below from a previous post of mine. A number of people have said that this is not needed but all I can say is that it fixed the problem for me. Costs nothing, takes 1/2 an hour

I cleaned the stepper motor and the idle was then wrong. It would slow to about 1200 rpm, then speed up briefly to about 1600rpm then slowly drop to about 800rpm where it would remain.
I originally asked Dream Machines and was told that if the stepper motor has been disconnected it must be set up again. I did as instructed and all was well, stupidly forgot to write the procedure down.
Recently went through the same procedure again and asked Chris Baldock at James Motor Sports (he is ex workshop manager for Walldonway ex TVR main dealer).
When told the procedure I remembered it from before to be the same so I'm thinking it must be right.
Procedure is;
With engine at operating temparature,
Disconnect stepper.
Ignition on for 10 secs (do not start engine).
Connect stepper.
Ignition on for 10 secs (do not start engine).
Ignition off for 10 secs.
Restart engine.

Interestingly Chris Baldock also told me that it is best to clean the throttle pot with carb cleaner at the same time;
Remove the pipe that links the Stepper motor to the throttle pot and clean it out,
Remove the pipe that connects the air flow meter to the throttle pot.
Screw the base idle screw right in, recording the number of turns. Then remove it.
Clean the hole that it sits in and also the butterfly and neck around it using a bit of rag to soak it up so not much goes into the engine.(Mine had a fair bit of gunge here)
Reassemble making sure the idle screw is wound right down and then out by the number of recorded turns.
It sounds a lot but only took about 1/2 hour and now idles perfectly

Thanks for taking the time to type all that out Keith! And V8S. I have now disconnected the Stepper once the engine had run up to operating temperature. Car now runs lovely . I suspect starting it from cold tomorrow morning will be interesting (although I could just rconnect stepper temporarily). Is there a manual choke conversation for these cars?.

As a more permanent solution I shall do all the things you have noted Keith.

Thanks for the help.

Is happy again

[blitzracing]

TVR keith said:

Perhaps your stepper motor needs resetting. I have copied the below from a previous post of mine. A number of people have said that this is not needed but all I can say is that it fixed the problem for me. Costs nothing, takes 1/2 an hour

I cleaned the stepper motor and the idle was then wrong. It would slow to about 1200 rpm, then speed up briefly to about 1600rpm then slowly drop to about 800rpm where it would remain.
I originally asked Dream Machines and was told that if the stepper motor has been disconnected it must be set up again. I did as instructed and all was well, stupidly forgot to write the procedure down.
Recently went through the same procedure again and asked Chris Baldock at James Motor Sports (he is ex workshop manager for Walldonway ex TVR main dealer).
When told the procedure I remembered it from before to be the same so I'm thinking it must be right.
Procedure is;
With engine at operating temparature,
Disconnect stepper.
Ignition on for 10 secs (do not start engine).
Connect stepper.
Ignition on for 10 secs (do not start engine).
Ignition off for 10 secs.
Restart engine.

This is definatley folk law and I think it refers to the older 14cu ecu. The Britsh v8 forum web pages also has a few errors of this type unfortunatley that has helped keep this myth going. There is NO stepper reset by resetting the ECU. The only reset occurs when you turn off the ignition, and the stepper then winds fully back ready for the next restart.

You can pull the cone out of the stepper to clean the shaft if you clamp it in a vice and pull the motor back whilst rocking it side to side. (its a bit harsh however). If you then screw the cone back in untill it just locks on its keyway, reconnect it and cycle the ignition. You should see it pull back smoothly to its home position as the ignition goes off. Just another note, some of the cheap steppers on Ebay (around £25) are poor copies and leak air around the motor.

Mark

[blitzracing]

A tip I read to keep the revs down, is to put something in the air bypass pipe to block it, but with a 6mm hole in it. It limits the aiflow to the stepper, but allows cold starting still.

Mark

[im]

blitzracing said:

A tip I read to keep the revs down, is to put something in the air bypass pipe to block it, but with a 6mm hole in it. It limits the aiflow to the stepper, but allows cold starting still.

Mark

Yep...I've got one in my car and it completely fixed this problem. I tried a 5.0, 5.4 and 6.0 mm restrictor and settled on the 5.4 as this settled the revs down to 950-970.

They were produced by SC Power who I believe were going to make and sell them publicly very soon.

Their website is here:

http://www.sc-power.co.uk/SC%20Power%20home.htm

If anybody is interested in one of these restrictors the phone number for SC-POWER is on the aforementioned web site.

Edited by im on Thursday 17th January 15:30

[TVR keith]

spend said:

Mmmmmmm... Stepper Folklore

I think Matron was right "just take an asparin, it will go away"

Dave

Dave,
I realise that you do have more knowledge than me, but;
How do you account for the fact that on every occasion the stepper has been disconnected on my car (2000 450) I had had this very problem? Going through this simple proceedure has on every occasion effected a permanent cure,
Keith