hi , i have a 1990 toyota pickup . it is a 2.4 engine . to start with the truck has 175.000

the truck ran great up until about a month ago and it began to loose power. so i put a new set of plugs in it . that did not solve power problem so i started running 89 fuel. that did not help either . soon the truck left me stranded because it just went dead . would turn over but no start. about 30 min later it started right up like a new truck.i got it home and decided i would try filters (fuel) . some one has placed one on the trucks rail so i replaced both filters. this did not help. the truck continued stalling regulary . i then found out that when the truck stalled i could take a screwdrive and tap on top of the fuel pump (in the tank) and the truck would start everytime (also the truck has a small body lift ) this told me to try fuel pump. 150.00$ later truck does not stall anymore but has no power. i have now noticed that when you are in the gas about 3/4 of full throttle the truck will sort of clear out and jerk in to a normal amount of power (like a powerband in a motorcycle ) but when you change gears the power is not there again . i put wires ,more plugs,cap, button and am running 93 octane gas 75 dollars a tank and still have the lack of power issue . any help would be greatly appreciated. also when truck is in a hard pull with lights on and i turn the heater on the whole truck jerks . please help

Hmm. You did about everything I could think of.
I don't think it's the issue, but have you checked compression?

The last bit about the heater making the truck jerk is making me think something is wrong with the charging system. Have you put a volt meter on the battery and see if it's charging? Also check for a loose connection on the battery. Worth a shot.

i have not checked the battery but will do that now and see what it says I am guessing about fourteen volts when running if that is wrong let me know .also thanks for reply

i put volt meter on battery when running and it was charging 14.35 to 14.55 so i guess that is working right my question is does the tps work with the mass air flow if so can this cause my problem any suggestions greatly appreciated

Ah, yes. Check the MAFS. It's the flapper style. The flapper should move smoothly with only a little pressure and flap back closed. Try cleaning it out with carb cleaner.

The other thing to check is spark. You should have a hot "blue" spark. Yellow will not cut it.
The battery voltage seems fine, but I would not rule out an electrical issue. Try measuring from inside the cab, from the lighter outlet or fuse block. It might be a bad ground between the battery and the engine and/or frame.

You need to measure the battery voltage under a load to get a meaningful reading.
Turn on everything possible then check the voltage @ idle RPMs.
It should be close to your previous readings (maybe a little lower).

Also check ALL the grounds for corrosion - batt neg to fender, firewall to engine fender to frame, etc.

battery voltage is the same under load the only difference is 14.55 without load and14.33 underload . battery to fender is broke i will have to get a wire tommorow also i have a new mafs thanks for the replys any more ideas please post them .

i replaced the grounds and still same problem flapper in mafs is just as it should be . could tps cause this .

Might be. I think the FSM has a test for the TPS. If that does not fix it, try posting in the http://yotatech.com/ More people on that forum.