Timing light skipping a fire.

[RockRanger]

I picked up a 1991 Ranger 4.0 5 speed a few months back. I am trying to get this thing to pass smog so I can daily drive it but it keeps failing emissions with slightly high HC and then gross polluter status for CO. NO is super low.

Anyway I hooked up my timing light and notice every 5 to 30 seconds it appears to miss a fire and the constant flash of the light goes out for a brief period and kicks back on. My googling skills are causing me to come up at a blank on what would cause this. I tried two different timing lights and both do the same thing.

I have replaced the following parts with slightly improved numbers but still bad:

Cat and full exhaust is all new
Spark plugs
Plug Wires
O2 sensor
Coil pack
CPS
TPS
MAS
Computer temp sensor
Thermostat (195 degree)
Unplugged and repluged in the computer
165 to 180 psi on a compression test.
60 psi of oil pressurr at cold startup.

The truck is running 32s with stock 3.55 gears.

If I run an KOER test when it is cold I will get code 44 for O2 sensor not switching. I will also get code 77 for opperator error on throttle test. If I let truck run and get to operating temp before I run the KOER test then I will only get the code 77. Truck seems to have great power for what it is.

I am thinking that the timing light cutting out might be the major issue I need to resolve but I am at a lost for what is causing it.

 

[boominXplorer]

Try running it with the alternator unplugged. I just had an issue that drove me up the wall with a 92 f150. Intermittently the timing would be out if wack and act like it's on 5 cylinders. Took the belt off to see if it was the smog pump and the truck ran perfectly. Put a shorter belt on to bypass smog pump and it went back to poop again. Figured out it was the alt at that point. Guess it had a bad diode causing interference as it was charging at 14.4.