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Engine falling off


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Anyone have any thoughts on this problem I am having?

When my S1 is sitting in the driveway and running I can rev the engine quite high 7-8000rpm without any problem, once I am out on the open road I can't seem to get the engine to rev over about 5000rpm before the power just "drops off " once I down shift ( lowering the rpms ) I get instant power back , until I get to the 5000ish rpm again.

There is no rev limiter on the car and all the electric stuff has either been replaced or rebuilt.

Fuel pump is new as well as the fuel filter.

Is it fuel or ignition?

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Can't remember the gearing, but how fast is 5000rpm in the various gears?

Peak torque would be below that sort of engine speed, peak power should be slightly higher, or at least the power available should mean it can pull beyond 5000rpm.

It could be fuel supply, and wouldn't show at no-load because you need a lot less fuel to maintain that engine speed without the load.

It could be spark/ timing, but I'd expect that to show up with little to no load, unless it's vacuum advance related (is yours vacuum advance?) because the vacuum would be high at no-load with the throttle only having to be partially open, but lower vacuum at full throttle opening when under load.

What's the real power like?

If the engine is becoming warn, and loosing power that could explain it very easily.


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Sounds just like a fuel pump on it's way out. Had this happen to mine and the degredation is really gradual. Only struck home when I got a new fuel pump and the car felt ten times smoother and drove like I'd had another 30 hp strapped in!




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Yup - sounds like a fuel pump, what made you replace the last one?

Another way to find the problem is to run a colourtune plug on a dynotune (rolling road). This will simulate the load and still allow you to view the mixture in each cylinder. Could be a float level issue?


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If you are getting a fuel supply issue be aware that this will be leaning your motor and making it vulnerable to engine damage.

I had my fuel block at the pressure regulator not long after I got the car as I didn't realise there was a filter there.


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