Strange engine issues - 93 3.0 V6

[CAminitruck]

Hey folks - any help is appreciated!!

A buddy gave me his 93 Ranger, 3.0 V6/ AT because he couldn't fix it himself. He cracked the radiator and went on to blow the HG (between cylinders, luckily, not between oil/coolant passages). I replaced the radiator, checked the heads and replaced the head gaskets. Also replaced all the spark plugs, spark plug wires, cap and rotor.

Engine was running rough, so I did a cylinder balance test and it pointed to #1 and #5. Compression checked out OK. Emissions check pointed to a lean miss. I replaced the injector on #5 - no improvement (injector is a reman unit, but 'new' and with a good warranty). I went out to run the compression test again, and forgot to disable the spark system. Engine started during the test on #5, and I noticed an intermittent knocking sound (even after the spark plug was put back in cyl 5 and the engine was running 'normally').

The engine is also periodically backfiring/stumbling. Seems smooth at higher RPM, but at idle is when the problem is most noticable.


Anyone have any ideas? I'm starting to go slightly batty...

 

[Wicked_Sludge]

did you check your base timing after having the engine apart? if so, you remembered to pull the SPOUT connector before hooking up your timing light, correct?

 

[CAminitruck]

did you check your base timing after having the engine apart? if so, you remembered to pull the SPOUT connector before hooking up your timing light, correct?

Yep and yep.. timing is within spec

 

[Wicked_Sludge]

id check for play in the distributor shaft, as this can cause low RPM drivability concerns. also make sure you didnt end up with vacuum leaks (especially if your getting a lean code) do to the recent work (overlooked vacuum line or an improperly installed gasket).