Posted: Fri Oct 29, 2010 10:56 pm
It's a Zetec - the crank sensor will be mounted directly into the block just as it left the factory and the trigger wheel will be built into the flywheel. Wiring between crank sensor and edis module is an outside possibility as although the engine runs fine with the ECU disconnected that may simply be because the module when running alone will continue to fire for a moment after losing sync. With limp-home that means you just stick at your fixed 10 degrees of advance irrespective of what the state of sync is, with the ECU connected the PIP signal coming and going would cause the perceived RPM to fluctuate, pushing the ECU between cells with radically differing timing values.
Which brings me on to another diagnostic test. Having thought about it I believe that the test I previously described (PIP connected SAW disconnected) is likely to yield the same quality of running as limp home but still exhibit the rapidly fluctuating RPM on the ECU readout. If that is the case then the next step is to fill all the load sites with 10 degrees of advance and reconnect SAW. The quality of running should be unchanged (ie still "better") but the RPM will still be jumping around. If so that proves that the problem is a sync issue, be that on the PIP wire or relating to the crank trigger
Which brings me on to another diagnostic test. Having thought about it I believe that the test I previously described (PIP connected SAW disconnected) is likely to yield the same quality of running as limp home but still exhibit the rapidly fluctuating RPM on the ECU readout. If that is the case then the next step is to fill all the load sites with 10 degrees of advance and reconnect SAW. The quality of running should be unchanged (ie still "better") but the RPM will still be jumping around. If so that proves that the problem is a sync issue, be that on the PIP wire or relating to the crank trigger