11 replies to this topic

[hilo92]

Yes, another rich running SPi; no groaning from the back!!

Just at the end of a rebuild for my '93 Cooper SPi. Starts on the button when cold at around 1200rpm then drops when the engine gets some warmth into it.

When the idle drops to 800-900rpm, the engine begins to hunt eventually idling around 500-700rpm when up to temperature.

During the rebuild, she has received new:

Water Temp Sensor
O2 Sensor
Vac pipes and elbows
Map filter.

Stepper motor has been indexed as per Haynes. HT Leads and coil are in good condition. Timing is within limits and the tappers have just been readjusted to suit cam. Vacuum from inlet manifold to ECU is good when cold and deteriotes with engine temperature. However fuel pressure from the pump is 1.2bar (Haynes states 1bar +/-4%).

Any help would be greatly appreciated :)

[minimat]

Valve clearances?Just done mine and so far seems better.

[FlyingScot]

What cam? High overlap can create issues on SPi.
Don't understand your point about vacuum deteriorating with engine temp?

FS

[hilo92]

Yup, valve clearances have been checked yesterday.

FS; all I mean is that when the hunt is rising in rpm, the vac drops and when the rpm decreases, the vac increases as you would expect. Vac gauge was placed between MAP filter and ECU.

[hilo92]

And the cam is a Kent MD274 although this rich running issue happened in the standard SPi can before the rebuild.

[FlyingScot]

Might be better to get it plugged into diagnostics to rule out a few things.....

Running it rich will do your engine and cat no good.

FS

[hilo92]

I've had it plugged in to a box of tricks and that was to no avail

I don't want it to be this rich believe me ha!

[FlyingScot]

I've had it plugged in to a box of tricks and that was to no avail
I don't want it to be this rich believe me ha!

What readings did you get? And what box of tricks ?
Diagnostics on MEMS isn't like modern technician diagnostics, you need to know what the readings tell you.
9/10 on more complicated issues there won't be a fault code logged.....

FS

[spiguy]

Unlikely to be the cause (maybe) but you should try taking the vac gauge off that line and put it on the red pipe which goes to the hot/cold air flap instead. That's where I have mine and it works very well there, just in case it is messing with the vacuum feed to the MAP sensor in any way.

[hilo92]

Update

It took its first MOT since I've owned it and passed with flying colours.

After replacing both vacuum elbows on the rear of the manifold (they were both cracked) and getting some heat cycles into the engine and exhaust, all it's running issues melted away.

Thank you very much to everyone who posted ideas, much appreciated :)

[Ado1379]

Glad you sorted it, I had the same problem and did all the above, in the end it was ECU and had to have rebuilt by ATP electronics!

[brivinci]

My 94 was acting up a bit recently. After coming to a stop, the idle would pause at 1500 and then slowly come down. I already replaced all my vac lines with silicone ones...all but one that is. The red line that runs from the airbox to the rear of the manifold. It has less then 5k miles on it and looked perfect. I finally got around to replacing it and guess what? The car now idles down to 800 perfectly. 

 

Lesson: Even a seemingly perfect and new OEM line is useless and should be replaced with silicone:-)