1996 S-10 hesitates under accelleration

The truck stumbles and hesitates under load, going up hill , passing, and I am at a loss. This thing has puzzled me for weeks. I have replaced everything the list is;

fuel pump
fuel filter
regulator
both coils
ignition module
crankshaft sensor
plug wires
plugs
map sensor
tps sensor

I had the ignition module tested on a Wells tester and it was good. I followed to a T the instructions for testing the fuel pump and it passed with flying colors. Plenty of flow and pressure. I have a pressure gauge installed and when driving the pressure is solid at 44 lbs.

My test box tells me that it starts doing this at about 21 degrees of advance. Above that it, when it's idling or cruising it runs fine. It runs great at idle and cruising. It only acts up when you try to accellerate.

I need some new ideas.

The fact that you mentioned you have replaced BOTH coils, tells me you have the 2.2L engine. Please clarify what engine you have as fuel pressure specs are different. If it has a 4.3L 44psi fuel pressure is too low. What is the fuel pressure with key on, engine off, and fuel pump running?

Yes it is a 2.2 L. The fuel pressure is 45 psi after you cycle the key about three times and holds at 40 psi after you turn the key off. When driving the pressure stays fairly constant between 40 and 45 psi. I still have the gauge installed if more info will help.

Thanks

Fuel pressure and leakdown are fine. Provided the fuel filter is not restricted, fuel delivery to the injectors is ok.

Does the SES light flash when it hesitates?

Is the SES light on and are there any DTC's in memory?

What brand and part number spark plugs and wires are you using?

How many miles are on this truck?
Did you do a compression test on each cylinder?

The engine is a fresh rebuild from a professional rebuilder. It was doing this before I replaced the engine. I replaced the engine under a warranty because of oil leaks from the rear seal and oil in the manifold and oil in #2 cylinder. Just for giggles I checked the compression and it's over 110 on all cylinders. The engine runs very smoothly, except when you accellerate.

I have followed ALL of the instructions on the Airtex website and the fuel pump tests good in every way.

Static pressure with the return line pinched is over 90 psi. Flow is very good and running pressure is 45 psi with about a 2 psi fluctuation when you apply the throttle. I don't see a restriction, kink or pinch, on any of the fuel lines. But, it still acts as if it needs more fuel, should I blow out the lines from the injector rail to the filter?

Mileage on this engine is under 500 miles. The truck has 330,000 and this is its third engine.

It has a new fuel regulator and I replaced all four of the injectors with no change in behavior.

The plugs are Autolite Platinum and the wires are fairly new but I have not replaced them since they appear good. When the car stumbles it acts like all of the cylinders are stumbling so I don't think it's the ignition. Of course I may be wrong since it still won't accellerate.

This engine has under 500 miles since new. The truck has more than 333,000 on it.

Sorry I don't know the plug number, they are what ever Advance recommends for this car. The wires are the premium ones they sell.

I forgot to mention, there are NO codes in the computer.

The light is not on and has not come on since this began.

Plug wires are like bath water, you can't tell by looking at them if they're good ;)

1,000 ohms maximum, per running inch is a good rule of thumb for testing the wires.

AC Delco 41-928 plugs will perform best in that engine, you might want to hold one of your Autolites side by side with an AC Delco and visually compare them. Look closely at the design of the taper seat and the distance from the seat to the ground electrode. Many times a cross reference will be close, but not a perfect interchange.

I'am thinking of a good clean throttle body, because you need alot of Air for that fuel mix.

I'll try those plugs you suggest. As for the clean throttle body, I cleaned it thorougly when I put in the engine last month. I'll post more after I change the plugs.

sorry so late to answer but i did have this problem then it went to tranny slippin to everything is fine back to missing in 3 & 4 change everything now i was told that the fuel injectors will cause this. so i am going to have the injectors checked out