Thread: Please Help, I'm reaching for the matches!

I have an issue with my 87 3.5 V8 the old Flapper with 4CU ECU. A while back the engine developed a miss, it's fine at idle but starts missing and backfires when I rev it.

Anyway as the old engine was a bit tired so I thought it best to pull it out and rebuild it as I had a spare complete engine from a parts car to put in it while the original is being rebuilt and the spare engine was running fine before removal.

After swapping the engines including the flapper the same problem is still there. I have checked all wiring and connections during the change over and everything dizzy, sensors, etc came with the other engine so I am ruling them out as causing the problem. I have also changed out the alternator, coil & injector power resistor, checked dizzy plugs, leads and fuel pressure seems fine also can't find any air leaks in hoses or the plenum.

I'm at a loss, I can still change out the ECU and all the relays but am I missing something or can someone please offer some advice on anything I might be overlooking.

Are you using the same dissy? I had a weak ignition amplifier which was fine at lower revs, but broke down with increasing revs, slowly got worse over 12 months or so.