36 replies to this topic

[MR J]

Hi All,

 

I've got a really irritating fault, when cold or just doing a short run my car runs fine, but on longer runs (over 25 miles) or when its hot outside when I let off the accelerator coming up to junctions etc or just slowing down to idle speed the engine cuts out. The engine restarts again without any issues but continues to cut out whenever i slow down.

 

Car is a 94 sprite, only mod is a K&N filter. Temperature gauge reads just below halfway all the time once warmed up, all vac pipes are clean and intact.

[spiguy]

could be an issue with stepper motor operation. If you think the stepper motor is working fine when the car is cold, then it could be a bad solder joint which only shows itself once the stepper motor circuit board heats up enough. Do you hear it indexing back to zero when you switch off the ignition? What is your cold idle speed roughly?  Has anyone messed with the adjustment on the the little throttle pin that the stepper motor acts on? 

[scrumpix]

As above replaced the stepper motor on mine with similar problem and now problem solved

[minisilverbullet]

i have a spare stepper can send it to you for 15.

[MR J]

Thanks for the info guys, i had suspected a stepper motor issue.

[MR J]

could be an issue with stepper motor operation. If you think the stepper motor is working fine when the car is cold, then it could be a bad solder joint which only shows itself once the stepper motor circuit board heats up enough. Do you hear it indexing back to zero when you switch off the ignition? What is your cold idle speed roughly?  Has anyone messed with the adjustment on the the little throttle pin that the stepper motor acts on? 

 

Yes, I can hear the stepper motor indexing when I turn off the ignition, Cold idle is about 900rpm ish, I've had the car 10 years and not touched the "screw you should never adjust"

 

I've bitten the bullet and bought a SP ARC and Rover Pod 1 and lead from ebay, question now is how do i use this to check the stepper and its adjustment??

[spiguy]

Hmm, I don't think you can do too much with the SP ACR (I have the same one) as far as stepper goes. You can do an actuator test which will operate the stepper over it's full operating range a couple of times, and you can watch the throttle plate move as this happens, but you can't get detailed info on number of steps or setup the stepper motor in any way. Maybe when you get the ACR you will find an error code / codes which give a clue? Not sure if faulty stepper operation throws a code or not.

 

in any case, if you do have a fault with the stepper, such as not working correctly when it heats up (transferred heat from a hot engine through the casing could take some time to raise it's temperature) then there must be a cause for this. The most likely cause would be soldering problems on the circuit board inside the stepper motor casing.

 

You could use your ACR to do an actuator test on the stepper when it is cold and everything seems to be working, and observe the movement of the throttle disc (or look side on from the passenger side and you will see the lever move). Then you could repeat this test when it is hot and the stalling issue occurs. Maybe you will then see that the stepper is not working at this time.

 

In the end if you do suspect a problem with the stepper, you will either have to replace it or pull it apart and look for dry solder joints, cracks etc, and repair them through most likely resoldering the bad joints.

 

This is what I did with mine, and I do suspect this is what will the problem with yours.

[MR J]

Thanks carlukemini,

 

I've just done a little bit more research and i've discovered that you're unable to adjust the stepper on a post 93 SPi with pod 1, but can with the later pod 3 if i'm not mistaken?

[spiguy]

Not too sure, but I really doubt that you are needing to adjust it anyway, if it works cold but not hot there has to be an intermittent fault causing this (assuming it is even the stepper of course). If you find and rectify the cause of the fault, then it should be OK. 

 

What happens if the car cuts out, then you start it again, will it immediately cut out if you don't hold the revs on the pedal?

[fergiemike]

Had a very similar issue on my MPI see http://www.theminifo...ittent-cut-out/

turned out to be the fuel purge valve.

hope you find it I know how annoying it is.

[MR J]

Once it's cut out and restarts it tends to idle, but hunts a bit as the ECU is trying to keep it running i think, it seems it's always on the verge of cutting out.

 

I'll wait for the code reader to arrive and hopefully start to gather a bit more useful information.

 

Just bought minisilverbullet's spare stepper also to try, for £15 i thought that was a good spare to have.

 

Thanks for the help guys

[FlyingScot]

Thanks carlukemini,
 
I've just done a little bit more research and i've discovered that you're unable to adjust the stepper on a post 93 SPi with pod 1, but can with the later pod 3 if i'm not mistaken?

For stepper set up on ACR system you need Rover Pod 3 or if you have ACR 4 you can use Rover 4, 5 or MAP pods - correct.

FS

[MR J]

Thanks for the info FS, I'll wait and see if I can get by with pod 1 before rushing into buying pod 3. It's the grey 2 line ACR I've bought.

[FlyingScot]

Good plan.
As Carlukemini has posted above the most common fault with the stepper is dry solder joints and since you have bagged a cheap spare from minisilverbullet you should be able to rule it out without needing pod 3.
For info The grey ACRs are basically the same as ACR2 blue ones and although a grey Rover 3 was never produced the blue Rover 3 plugs into ACR (just looks a bit odd) its the last model compatible with 2 line readers (ACR and ACR2). Typically they are better value (cheaper) than the blue ones anyway but for some reason folks prefer blue....

FS

Edited by FlyingScot, 22 April 2015 - 12:41 AM.

[spiguy]

Agree with FS, you have the spare stepper so you shouldn't need to get into the nitty gritty details of the stepper operation. Even without a spare one, it won't really help you to have any more information. Once you have decided the stepper is suspect, you would need to open it up to look for faults. Or in your case as you have the spare, swap it.  I would be trying to decide if the stepper is suspect, and if so then just swap it out for your spare and see if it solves the problem.