When did this surging become noticeable? After you did some work?

What timing set did you get? Was it adjustable (e.g., options for retard/advance)?

What brand are the spark plugs? The platinum high dollar type plugs tend to not do well in these engines unless coupled with other mods. The champion copper plugs are the most ideal.

Can you get a compression check done?

Can you do a video of the symptom, like watching the tach as it occurs?

For any/all the sensors that you have replaced, what brand and store from? Some sensors from general auto parts stores don't play well. Getting from the dealer are the only way for some.

 

No, it has always seemed to surge. I haven't owned the truck for long, the chassis has lots of miles and I believe it is on its 2nd engine and transmission, likely a pick-n-pull special. It's a bonafide hunk of crap.

It was a basic Cloyes timing set, non-adjustable.

Don't recall; they are not platinums.

I could probably do both; might take a few days to get around to it.

I don't recall the brand of the governor pressure sensor. The intake temp sensor has been the only sensor I've replaced on the engine; it was Autozone's house brand (Duralast?), but the problem existed before I replaced this sensor.


I have another thought...the fuel-pressure regulator (as a component of the fuel-pump assembly in the tank) does not have a direct reference to manifold pressure. Is the FPR a static pressure regulator, or might it be vacuum-referenced through the EVAP system?

 

Static system. It attempts to maintain constant pressure. So far as I know, it is not modulated in any way.

 

Fuel pressure is a stand alone regulator on the FP. I don't think that's the prob, but you probably should check the pressure with an inexpensive gauge, just to eliminate it as the prob.

 

If the fuel pressure is oscillating at WOT, it absolutely would create the problems I'm experiencing. I'll add this to the list of things to check...