My stage 3 4x4 had developed a strange missfire. I start it up in morning no problem. Let heat up, start giving it boost and its fine, doesent miss a beat. I shut it off at tesco or whatever, after 10 mins of shutdown i fire it bk up and its fine. Get round cuple corners, give it boost and it dropes down like a missfire. Only on boost. Drive around for few mins and eventualy goes away. Just put new plugs gapd to .6 in it, new dissy n rottor arm. Not checked gapping on phase sensor or that yet. Very strange its only when shut doen and fired back up.
Stage 3 usual, t34,3 bar map, greens, intercooler, MSD revolution chip, 044 pump with new wiring. Any input wld be apreciated

Cheers Richie

 

My money is on the bulkhead loom plugs being the cause, common fault on a 4x4

 

Cheers for the reply i will look in2 this. Do the plugs corrode?

 

What you have to remember is that you have got the original factory wiring looms/plugs and connectors which are all now at least 26 years old. Corrosion and dry joints etc can give electrical problems which are very hard to pinpoint as they are very often intermittent faults.
Before I had wasted spark ignition fitted on my 1990 2wd I replaced my engine, 044 fuel pump and radiator fans looms with updated modern ones and my car has not missed a beat since.

 

I realy do want the wasted spark setup! Need to get it on the santa list. I also have replaced 044 pump and wiring loom last year. Also fan looms

 

Well you have eliminated 2 potential sources of electrical problem areas, now when you can afford it do the engine bay wiring looms and everything should be ready for the wasted spark ignition.

 

Have you read the ecu fault codes

 

What he said,

When the mis-fire occurs what is the rev counter doing? If it's jumping around and going skyward it's time for a new engine loom