6 replies to this topic

[Mikey7094]

Hi all, I have a few minor but annoying issues with my ’94 spi cooper. I think I need very expert advice to sort it out!

It’s mainly the idle speed, which sometimes drops really low – it falls to 500, and keeps falling to 400, and then I put my foot on the throttle for fear of stalling. This is a pain in the arse at junctions, but sometimes it’s absolutely fine, and it idles completely normally.

I’ve also noticed that it stutters briefly when you rev it, but only if you rev it quickly – it will stutter for a split second and then rev. This doesn’t happen when you rev it gradually.

And I’ve noticed that the idle, when it’s at normal speed, is slightly unsettled. You can see the rev needle hopping up and down, just a tiny bit, which I understand could be a problem with the throttle potentiometer... Apparently there’s a little needle that gets sticky... As you can tell I don’t know much about this. Could all these problems be down to the potentiometer?

I really want to sort this as the car’s just been in the garage, which cost me a small fortune, so I hate to think that it’s still not right. It went in because it was running horribly rich, had a flat spot and would back off under full throttle. They replaced a relay, the manifold heater element, the lambda sensor, the spark plugs and finally the whole injection unit, which seemed to be the main problem. (If it helps, they replaced the injection unit with a second hand one.) They also fixed an air leak in the inlet manifold. This all worked wonders – it’s not running rich any more and has no problems accelerating, but as usual it’s just revealed more problems...

Any ideas would be very much appreciated.

Mike

[minisilverbullet]

Hi Mikey

You will be pleased to hear that this is very common problem, unfortunately it appears there can be one of many culprits.

The best bet would be to get the car onto a diagnostics code reader. I would recommend a mini specialist as they will have the suitable kit for an SPI. You might also get lucky at garages that where previously rover or even an mg garage.

Does the car ever stall totally under sharp breaking? I had this very problem twinned with a really "bouncy" idle. For me it turned out to be the fuel trap. Which is a small black box (size of a match box), which stops fuel vapour entering the ECU. This little box connects to two vacuum pipes. I would recommend replacing this, it should be relatively cheap and you can for sure do it yourself.

Other than that.... as i said it could be a number of things: an air leak (but your garage has just checked that), could be a faulty potentiometer (can you hear it clicking when you turn the ignition off?

[minisilverbullet]

infact this is the fuel trap http://minispares.co...a...7835&title=

[Racing Gold]

infact this is the fuel trap http://minispares.co...a...7835&title=

As the garage replaced the whole injection unit!!!!!,which seems to suggest they may not be Mini specialists, did they set the stepper motor afterwards? Nearly cutting out at junctions and when suddenly braking is a classic sign, especially if you did not have that particular problem before. Also, did they give you your old injection unit back because you can use the throttle pot on that as a spare. I'd put my code reader on it for you but may be a bit far away. Slark's at Amesbury, (Slark Racing) would stick there code reader on it, they are a bit closer

[Mikey7094]

Thanks for the help guys

Is the potentiometer part of the stepper motor, then? Is the "needle" I ignorantly speak of that little arm that comes out of the stepper motor to catch the throttle? I really don't know much about fuel injection, I shouldn't own an spi at all...

The garage I sent it to was a mini specialist - Green & White near Durham (that's right, I'm not in Somerset at the moment - I'm a student, you see), which was recommended to me by someone on this forum. They only replaced the injection unit as a last resort, having done a diagnostic test twice, after which it was still running really rich. They replaced the injection unit and hey presto, that fixed it. They kept the old one - I do wish I'd asked for it back!

But I suppose they might not have set the stepper motor properly. How do you set up a stepper motor? Or do you just have to buy a new one? I can definitely hear it click when the ignition is turned off.

I haven't done much sharp braking recently, but it hasn't stalled under braking. The engine doesn't abruptly die - or at least it hasn't yet - the revs just slowly sink lower and lower.

And about the fuel trap - does it just get blocked up? I suppose if my car was running rich that could happen.

Cheers

Mike

Edited by Mikey7094, 04 December 2010 - 11:26 PM.

[Phil-R]

With the ignition on, open and close the throttle about 5 times. You should hear a load of clicking then and the stepper motor (needle) moving in and out as it resets. This really needs to be done after any major engine work. Also open the throttle until the needle moves out to catch the throttle. When you release the throttle the adjuster screw should touch the end of the stepper motor needle. If not, it will need to be adjusted.

With the fuel trap, try undoing the pipe at the ECU and checking you can blow through the pipe. The trap has one black nozzle and one green one. Make sure green side goes to the ECU, and any fuel will drain towards the manifold.

Edited by chrome, 05 December 2010 - 11:45 PM.

[Mikey7094]

With the ignition on, open and close the throttle about 5 times. You should hear a load of clicking then and the stepper motor (needle) moving in and out as it resets. This really needs to be done after any major engine work. Also open the throttle until the needle moves out to catch the throttle. When you release the throttle the adjuster screw should touch the end of the stepper motor needle. If not, it will need to be adjusted.

With the fuel trap, try undoing the pipe at the ECU and checking you can blow through the pipe. The trap has one black nozzle and one green one. Make sure green side goes to the ECU, and any fuel will drain towards the manifold.

Right, I'll try this when I next get a moment, and I'll get back to you.

Mike