hello everyone

Im working in a 1996 Ranger 2.3 4x2. I just installed a rebuilt 2.3 from a brick and mortar and right from the fist start the cylinder #4 is misfiring. The previous engine was replaced due to loss of compression in #3 and #4.
The spark plugs, coils, wires and #4 injector are new. The compression test is as follows #1 155psi, #2 155psi, #3 155psi, #4 145psi
upon starting the engine in the first few revolutions perhaps a second of two the engine sounds good and feels like there is no misfire but right after the misfires starts and more noticeable when accelerating.
im sure im getting spark and ignition pulses ( checked )

any ideas what it could be happening ? what else should i check?

tia

 

You need fuel, air, spark and compression to produce power and run.... If you have a multi-coil box, with all plug wires in one, you have a 'lost spark'
ignition where 1&4, 2&3 fire on every revolution, as pairs. One cylinder will be on compression, the other exhaust, but both plugs fire at the same
time. You can check with a timing light clamping on each wire in turn to see the timing light flicker. w/o a light, you can pull the plug wire from the
tip of the plug(loosen ahead of time) and hold it near the spark plug metal tip. It should spark...
So, if you have spark, you could lack fuel. The injector could be clogging, or sticking. Adding fuel through the intake might make it rich enough to
fire or not. You could feel the injector to see if it is clicking.
If you have an air leak, you can use a hose connected to a porpane torch tank, and let propane loose around the intake manifold. If leaky, the
propane would make the mix good, and the cylinder would fire.
Final thought is that the hydraulic 'lifter' support that holds one end of the cam follower may be at its limit, and holding the valve open once you
get pressure in the system. If the lifter is sticky, it can hold the follower up too high and it will keep the valve from seating.
THIS is not common, but all the other things seem less likely.
You can remove the #4 supports and replace them, or check that they can be compressed, leaked down so there is clearance when at TDC.
If the lifter is pumping up, and not leaking oil as designed, it can hold the valve open, possibly just off the seat. There is a specification for
the valve clearance with the lifter compressed, somewhere around .060" (I do NOT remember the exact) If less, it may cause the problem
you report. The compression value is off compared to all the rest... and that's the cylinder with the problem.
Have you talked to your vendor? Maybe they will provide assistance and you won't have to deal with it. You want to be sure you have no
intake leaks, bad or worn plugs, wires, coil, etc. And that your injectors work perfectly.
You could disconnect the #4 injector to see if it was working.. last thought.
tom