Missing in action

[hydrosmith]

My 1992 Ranger STX SC 4wd 4.0 A4LD has an engine miss I cannot find. Thus far I have replaced the MAF sensor, coil pack and O2 sensor(which did get rid of a "lean" code). The plug wires were new 4 months ago as were the spark plugs. The computer is not throwing me any engine codes right now. All the vacuum hoses seem to be in good shape and everything is connected.

The only other defect it has right now is a small oil leak from the passenger side valve cover. It couldn't be getting a vacuum leak from that could it?

 

[Spott]

Have you pulled the plugs and looked for funny colors?

That might provide a clue.

 

[bmerr98]

Double check spark plug gaps...

 

[deathcyte]

All the time? Cold? Hot? At idle? Under load?
A bad fuel injector? You checked all the ignition components, but did you check the fuel side? What about compression? A valve hanging open will cause a miss, did it happen all at once? Or gradually?

 

[hydrosmith]

All the time? Cold? Hot? At idle? Under load?
A bad fuel injector? You checked all the ignition components, but did you check the fuel side? What about compression? A valve hanging open will cause a miss, did it happen all at once? Or gradually?

All the time? Cold? At idle?: No not all the time, really rough when cold and smooth's out somewhat after about a minute above 1200 rpm's. Warmup idle is smooth as silk.

Under load? : Yes definitely!

Bad fuel injector? : I don't know how to check for that yet

Compression? : I don't have a compression tester

Happen all at once? : No, it is something that has become progressively worse, going from occasionally over the past month to most of the time the past three days. I didn't have the money earlier but I do now as long as it's not real serious.

As I am typing this the fuel pressure regulator comes to mind or a clogged convertor and both are original. Any thoughts?

I will pull the spark plugs and look those over.

 

[Mazda]

I had a similar issue like yours.. I had a cracked plug in the number 4 cylinder.

 

[hydrosmith]

Problem solved. Removed NGK spark plugs and installed Autolite plugs. I will not buy NGK plugs again. They lasted only 5 months-the electrodes erroded.