Outer Limits 4x4 Board

The woodruff key on the crank would have been worn badly and the crank gear would have been moving. The sensor plate is attatched to the gear and this would have caused the ignition timing to become quite retarded causing the lack of power.

Does the computer advance the timing enough at higher revs to produce enough power?

would the worn key cause the valve timing to retard as well as spark timing?

Yes bothe the valve and ignition timing would be retarded. As for it coming good at high revs i'm not so sure.

If the igntiion was retarded - say by 10 Degrees, it would be very noticable at low reves eg idle, because there is an initial advance of about 10 Degrees at idle. This is to allow for a finite time for the air/fuel charge to ignite at the right time - at Top Dead Centre. If you are too retarded, it fires before TDC and the engine has to work against the expanding gas in the engine.

At higher revs, you need a lot more advance because the time to ignite the charge is still the same, so they advance the spark a lot more - up to 30 Degrees before TDC - to compensate for teh delay. If it was only 20 Degrees, the effect would not be as pronounced as at lower speeds.

As far as I know, the engine management system senses the engine position via the TDC sensor, and it then computes when to fire the spark taking into account the speed, throttle setting and a lot of other factors. But it still relies on the TDC sensor as a base for the timing, so it probably was still retarded, but in percentage terms, not as badly when it was revving harder.