spi reving problem
Turbo Mini Forums

hi guys,
ive been working on spi,
we have fitted it to an earlier mini, and got it running,
it ticks over fine and will rev up nicely for about a minute,
then a problem occurs it will rev up to a certain point then cut back to idle, even with the accelerator on the floor it still only revs to a certain point.
we have checked everything is connected up
but still no joy.

it does have a 3 pin diagnostic port, and was wondering if there is a cheating way of using it?
or if you have any other ideas that would be great:)

cheers stu

Hi,
Map sensor pipe is about the only thing I can think of at the moment. Did it run ok in the previous car?
Have you tried driving it to see if it still does it?
Cheers,
Gavin :)

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its not legal at the minute to take it for a drive, dont know if it ran or not the car was scrap, for body reasons though.

i think i know the answer to this. They have a throttle switch on the linkage inside the car. If that isn't working, there is a rev limit at about 3.5k no matter what the throttle is doing.

Found it on my old spi, rev it in the car, it was fine. Rev it using the linkage on the side of the throttle body, wouldn't go higher than about 3.5k.

As you've retro fitted it, it could be a possibility.

mine didnt have that switch........

hmm, sprocket knows a lot about these, so he's probably the man to ask.

ah ok will investigate that switch i know it has one, any ideas how it works?

i noticed the exact same thing on my old spi, when reving it using the tb linkage it would rev/die/rev/die

"Turbo's make torque, and torque makes fun"

"did you know you can toast potato waffles?"

we found the accelerator switch wasnt in place so bolted it up, unfortunatly it made no difference, doesnt mean its not faulty though!
we did notice there was no purge valve, (after pulling the loom apart to find the hidden wires)
so trying to locate one off them.
tomorrow im borrowing a codereader from a garage so will see what that comes up with

cheers guys

my mates snap on code reader never worked on my spi, not sure why?

"Turbo's make torque, and torque makes fun"

"did you know you can toast potato waffles?"

it didnt flag up any codes.
but it did say the throttle switch wasnt turning on!
so had a think and decided the pedal probably breaks the circuit when its being used. we unpluged the sensor so it would be on all the time.
this worked and it reved freely!
although it does idle a bit high so we are gonna try to get a new switch.

cheers for your help guys

The early SPI up to 93 (two plug ECU)used a switch on the throttle pedal to tell the ECU that it was in an idle state. All later SPi used the TPS to determine the engine was idle.

If the switch is nott working and elling the ECU that it is in an idles state but depressing the tthrottle pedal increases the engine speed. Idle speed control trys o bring enginee speed back down to idle of 850 rpm first by reducing steppeer position. when the steppeer reaches 0 stepps, the igniion advance is allowed to rettard.

In thtis incorrec situation what you get is an engine at around 2,5k rpm wih near zero advance, causing hesitation, missfiring and, backfire into the inlet manifold, with flames that will take your eyebrows off. If left unchecked and the cat is still fitted, the excess hydrocarbons in the exhaust caused by incomplete combustion will melt the cat, sooner rather than later and restrict the exhaust, adding to the already bad situation.

The accelerator pedal for these cars has a small circular disc welded to the pedal just below the cable for the swich o bear against, and there is a spring that pulls the pedal back to its natural position. The spring was an after tthought as if the pedal did no return fully tthee enginee would not idle correctly.

he purge valve wont mater as long as you plug the pipes off.

Make sure you adjust the throttle cable correcly by indexing the stepper motor. Its explained in the Haynes book.

Make sure all small black, red and yellow vacuum line ends are in excellent condition, better still replace all the important black ones with Samco vac tubing.

Sounds like you have fount the problem :)

Oh and adjust the idle screw so that the diagnostic shows the stepper at around 40 steps

cheers mate

whey!! Did I guess something correctly!?

would seem so lol

we found the sensor was ok, but because we were using the original pedals it didnt have a steel plate on the back!
fitting one solved the problem.

just for future reference really

stu