Strange engine miss

[ajtbussen]

My 1990 range rover has a miss between 2000 and 2500 rpms under high electrical load. Items already checked are:
All engine bay grounds.
New plugs, wires, cap, rotor
Distributor
Timing
Coil
Alternator bench test OK
Injectors test good from ecu
Swapped ecu
Battery good
Fuel pressure good. Used PT's new pressure gage manifold for early engines. 32 psi.

I'm going to check the ignition switch and swap ignition amplifier.
Anyone have any other ideas?

 

[morerover]

I had the exact same symptoms on my 93 RRC and it was cured with a new alternator. The original alternator checked out fine with 14+V DC charging, but there was a measurable AC component that was apparently not filtered by the rectifier and was affecting the engine ECU. John Robison helped me to diagnose it and suggested the solution as he suspected the rectifier was at fault based on the multimeter readings.

 

[singingcamel]

Run it when dark and look for arching.

 

[ajtbussen]

I replaced the distributor with a Pertronix from D&D and problem is solved. Must have been a noisy pick up or amplifier. Very easy conversion. Lots more power across the rpm range. Thanks for all the help PT!

 

[ajtbussen]

Well the truck died while the boss was driving. Checked all connections and found nothing wrong. Still I had no spark. It turns out the distributor rotor supplied with the pertronx distributor is as good as all the other after market rotors. I put a Lucas rotor inl and it goes! Who woulda thunk? Everything is good now.

 

[ajtbussen]

So far I'm averaging 18 mpg. Even with the AC running I'm getting almost 17mpg.
Really happy with this setup.