Gents, I'm trying to help a friend with his '89 4.0
He just installed a new/rebuilt engine fron AutoZone..A long block.
It's got a steady miss at all speeds. He's got fuel injection and a distributor with fixed timing...old school stuff.
I've done resistance check on each injector and they all showed electricly OK @ 12/13 Ohms
I clamped timing light on each spark plug wire and they all get fire.
However, his idle vac is only 5", whereas I know it should be pulling way up around 16-20"
I did propane bottle hose test all around his intake manny but didn't find a leak (couldn't really get in there)
Pulled all his plugs and they looked like new with none fouled...hmmm
I can't actually pop test injectors and I'm about to suggest he go buy one new one and we swap it into each cylinder to see if miss goes away and vac improves.
You guys got any suggestions ? TX