24 replies to this topic

[minisilverbullet]

96 SPI

Recently and intermittently i have had some sort of problem with accelerator sticking. Its not the actual pedal which sticks, but it feels like even when im not accelerating the engine is still revving, at a constant rev. it normally happens when decelerating from speed. and the car doesnt seem to slow down as quick!

Also when waiting at lights with my foot on the clutch the car is revving more than normal it seems to idle at around 2 on the rev counter.

This does not happen all the time!

The times its happened I have turned the engine off and restarted and normal service is ressumed.

sometimes it sticks and the car seems to drive its self at a constant speed.

It all seems very odd to me! perhaps unrelated I am about to change to the engine steady bushes as i can here the engine creaking when accelerating or decelerating , engaging the clutch etc. I thought that this was caused by the engine steady bushes being worn but it may be related to the above problem.

Ive checked the throttle cable and it looks clear and in good condition!


As I mentiond I need new enginge steady busehes soooo the excessive movement of the engine could be provide some sort of obstruction to the cable sometimes. OR?

Any other ideas out there? its a bit unsettling when the car wants to drive itself. A gear change or popping the car into nuetral soon stops the excessive reving !


Thanks in advance for any help.

Cheers.

[minisilverbullet]

Although i am pretty clueless! After a quick google search i seem to have narrowed the problem down too either (but what do i know)

"air cleaner air temperature control"

"inlet air temp sensor"

The problem only really occurs after driving on the motor way : I assume it must be somethig to do with the engine running warm and one of teh above sensors /systems no functioniang as they should.

Another possibility may be the throttle body.

as i say i just googled around and found this info, so i could be way off!

Help much appreciatted!

[xrocketengineer]

Hi,

Start with this:
http://www.theminifo...showtopic=20533
The vacuum lines from the intake manifold to the MAP sensor on the ECU and to the Thermac valve on the air filter inlet need to be near perfect. My car was idling at around 2000 RPM. Replaced the cracked elbows for the Thermac valve at the manifold and at the air filter. The RPM came down but then idle was erratic and the engine would die. Then found the other line going to the MAP sensor had collapsed on the manifold port. Replaced the line and all problems went away.

Hope that helps,

Ivan

[minisilverbullet]

Cheers Ivan,

but I dont think its the same issue,

I can drive the car for days with out a peep of the problem and then like a bad surprise it seems the throttle sticks open, when this hapens thats when i feel the high revs and the car wants to pull away on its own. If i turn the engien off, the car starts as normal! and the problem goes away until teh next time.

[Blackivory]

I think you also have to check the stepper motor.

[Blackivory]

Minisilverbullet,
Have you solved the problem?

Please update.

[minisilverbullet]

Hi black ivory!

the probelms seemed to stop when i reindexed the starter motor!

It came back last week and i reindexed it again and its fine!

I not sure how it should sound but it seemed very tired and laboured when re positioning itself (the starter motor), so your diagnosis is right!

Have you had experience with this problem before?

Cheers

Craig

[Sprocket]

The stepper motor does click, but I cannot understand what you mean by laboured. It makes a regular clicking sound, no hesitation, each click is the same as the other.

I still think your problem is something to do with the throttle cable or linkage. It could also be related to the carpet or mats in the car.

[minisilverbullet]

I checked the cable all the way today and it seems fine!

BUT.... shortly afterwards took the car for a drive and it got stuck open at around 2000 rpm (the car was stationary), i put the car into neutral, reved to 3000 and it stuck there, reved to 4000 stayed there, reved to 5000, stayed here etc!

What would be causing this!

[Alpenflitzer]

I checked the cable all the way today and it seems fine!

BUT.... shortly afterwards took the car for a drive and it got stuck open at around 2000 rpm (the car was stationary), i put the car into neutral, reved to 3000 and it stuck there, reved to 4000 stayed there, reved to 5000, stayed here etc!

What would be causing this!

I rgeularly use throttle body cleaner and since then have no problem.
Regards Bill

[Blackivory]

Minisilverbullet, Thanks for the update.

I also got problem with my Spi, unable to solve it so far.

It has erratic idle occationally and unpredictably. I have checked all the vac pipes as well as checked and resoldered the stepper motor, but the problem is still there.

I posted my problem in http://www.theminifo...howtopic=139853

Unfortunately, no one has replied.

Here is my post:
========================================
Hello there from Thailand,
Recently, my mini cooper experiences strange rev when driving and idling. A couple months ago, I set the lost-motion gap as per Hanes/Sprocket's advice (Thanks, man) and after that it had run pretty well, no problem at all. CTS and guage are okay showing at around mid range. It just happened a couple week ago while I was driving it, I think at that time was around 1500 rpm, and suddenly the engine was kind of revving up and down between 1300-2000 rpm resulting in shaking the car like it was hiccuping, but the engine did not stop. This happens unpredictably and I notice that sometimes it happens at around 1400-1500 rpm, but still cannot be so sure since it happens in the morning as well when it is first started, engine is still cold.

Last weekend, I cleaned the throttle linkage and stepper motor and checked all the vac pipes. Everything was fine, but the symptom was still there just happened again yesterday evening.

I suspect the stepper motor and throttle pot.

Does anybody experinece this?

Much appreciate for your help and advice.

Update:

When this happens while idling I take the air filter out and notice that the injector stops squirting, I would say just milli secs, then the rev will come down due to no fuel. The engine responds by, I think, increasing fuel pressure resulting in rich mixture going to the engine. As a result of that the rev goes up. This happens back and forth, thus, the rev will be going up and down, up and down, ..

Any ideas would be highly appreciated. Thanks a lot in advance.

=========================================

Unfortunately, no one has replied.

Last week, I have replaced the stepper motor, but cannot solve the problem.

I am not sure whether it is coming from crank shaft position sensor or throttle position sensor.

Much appreciate if someone can explain what will happen if those two are faulty or degradable (so that it cannot work properly).

[minisilverbullet]

Minisilverbullet, Thanks for the update.

I also got problem with my Spi, unable to solve it so far.

It has erratic idle occationally and unpredictably. I have checked all the vac pipes as well as checked and resoldered the stepper motor, but the problem is still there.

I posted my problem in http://www.theminifo...howtopic=139853

Unfortunately, no one has replied.

Here is my post:
========================================
Hello there from Thailand,
Recently, my mini cooper experiences strange rev when driving and idling. A couple months ago, I set the lost-motion gap as per Hanes/Sprocket's advice (Thanks, man) and after that it had run pretty well, no problem at all. CTS and guage are okay showing at around mid range. It just happened a couple week ago while I was driving it, I think at that time was around 1500 rpm, and suddenly the engine was kind of revving up and down between 1300-2000 rpm resulting in shaking the car like it was hiccuping, but the engine did not stop. This happens unpredictably and I notice that sometimes it happens at around 1400-1500 rpm, but still cannot be so sure since it happens in the morning as well when it is first started, engine is still cold.

Last weekend, I cleaned the throttle linkage and stepper motor and checked all the vac pipes. Everything was fine, but the symptom was still there just happened again yesterday evening.

I suspect the stepper motor and throttle pot.

Does anybody experinece this?

Much appreciate for your help and advice.

Update:

When this happens while idling I take the air filter out and notice that the injector stops squirting, I would say just milli secs, then the rev will come down due to no fuel. The engine responds by, I think, increasing fuel pressure resulting in rich mixture going to the engine. As a result of that the rev goes up. This happens back and forth, thus, the rev will be going up and down, up and down, ..

Any ideas would be highly appreciated. Thanks a lot in advance.

=========================================

Unfortunately, no one has replied.

Last week, I have replaced the stepper motor, but cannot solve the problem.

I am not sure whether it is coming from crank shaft position sensor or throttle position sensor.

Much appreciate if someone can explain what will happen if those two are faulty or degradable (so that it cannot work properly).

Sounds similar to my problem

Throttle sticking open - we are now sure that the throttle cable must at least be somewhat responsible. I have a new one ready to go in.

Erratic idle - I used a bottle of injection cleaner which ypu put in the fuel tank, it did seem to help as the car ran alot smoother and the erratic idle has happend, once since then.

Have you read through the pinned topics in the spi/mpi section, lots of info there which could be useful.

[Blackivory]

Minisilverbullet, thanks a lot for the suggestion.

I still keep reading all the other posts to find the solution for my problem.

Last weekend, I replaced all the vac pipes, cleaned up and replaced gasket of the throttle body, changed oil, fixed the oil leak on the tube connecting between top of oil filter and engine and found out that there was some oil film covering on the crank shaft sensor ( I think this came from the leak tube I just mentioned) and already cleaned it.

I do not think a thin film of oil will affect the crank shaft sensor reading, but I could be wrong about this.

However, unfortunately, the problem was still there. It happened on the next day

But it disappeared in the evening when I took it for a ride. This is so unpredictable.

How long does it take to have ECU to relearn the engine and adjust itself? I am so curious.

Like informed earlier, When this happens while idling I take the air filter out and notice that the injector stops squirting, I would say just milli secs, then the rev will come down due to no fuel. The engine responds by, I think, increasing fuel pressure resulting in rich mixture going to the engine. As a result of that the rev goes up. This happens back and forth, thus, the rev will be going up and down, up and down, .. and sometimes the rev is just going up to 2000 rpm and stays there.

If this happens while driving I can notice that the car is like hitting a curb (like it is hiccuping) I am quite sure that this is coming from the injector stops squirting.

Is this also releated to O2 sensor malfunction?

Appreciate for any inputs here.

[DustyM]

Blackivory & Minisilverbullet,

I'm handy with a spanner but not a mechanic! Quite recently I had a similar experience with my '94 1275 cooper.

Very randomly the car would miss for a split second. This could be at any speed and under acceleration or when decelerating (deceleration would not be smooth!) It came and went so suddenly that I assumed it was an ignition problem so I changed everything from plugs to coil - to no avail.
At this stage, the problem was difficult to diagnose as it may occur for only a split second in every half hours driving!
I changed lambda sensor, air temp sensor and coolant sensor as well as checking the capillary tubes, stepper motor operation, cotton wool in MAP sensor etc. etc. etc!!
As time went on the symptoms got worse to include a rough idle (sometimes cutting out) and a high idle c.2300RPM again, only periodically. The plugs were black. On one of the occasions when it was idling rough, i got to fit a set of ignition spark detectors which confirmed that the problem wasn't related to the ignition system. I carefully watched the injector on this occasion also and it behaved very similarly to how you have already described - not injecting for a second followed by a long, wide pulse.
After this I went through the loom to check for any breaks or loose connections. It was while I was doing this that I noticed when I pulled on the wires from the throttle potentiometer that the symptoms began and stopped when I let go.
On further investigation, when I tapped the potentiometer with a spanner the idle would get rough and slowly get better a few seconds after I had stopped. When the car was idling badly, it would immediately improve when I unplugged the potentiometer and disimprove when it was plugged in again. After 'playing' around with this for a while I was confident that this was the root of my problem and got on to Somerford Mini for a new potentiometer - Once installed the car has run perfectly!
On examination, the old potentiometer 'lever' does not move smoothly like the new one and sometimes when pushed into the throttle fully open position it stops about half way and doesn't continue to the closed position without a nudge (or two)!

It is an expensive item so I wouldn't rush into buying one unless I was reasonably confident that it would do the trick - as already mentioned these things aren't known to fail regularly.

Hopefully this might shed some light on the problem.

[Blackivory]

DustyM,
Appreciate for the input here. At least, I know that someone else also experiences the same problem.

I will definitely check the TPS and will report back soon.

Hope that this will solve the problem.