1991 4.3 engine missing, low on power

[roadxing]

Ok to make a long story short my truck missing real bad and it takes a lot of effort to get up to speed. Seems like its bogging down when you give it gas. Will not hold speed going up hills.
Already replaced:
Plugs, wire, distributor, cap, rotor, timing chain, fuel filter.
Swapped around MAP, idle, throttle position, VSS, ECM, and a couple other parts and no difference was detected. Checked grounds and most of the wiring.
No vacuum leaks have been found.
The only code i get from time to time is that its running lean, but thats not a supprise seeing that its missing real bad by the time the check engine light comes on.

50% of the time when i start it up it idles perfect but still cant be driven without it bogging down real bad when i give it anymore throttle than getting it over 1000 rpms.

ANY suggestions would be greatly appreciated.

Thank you

[manicmechanix]

This is a throttle body injection right? Have you checked the fuel pressure? TBIs aren't prone to injector clogging but it can happen. You also want to check the resistance on the injectors. You didn't mention if you changed out the O2 sensor. How is the engine mechanical condition, have you ran a compression check and do you have a good and steady 17in-20in of vacuum?

[roadxing]

Im stuck with the bare basics when it comes to tools. Im setting a few hundred miles from my house. So i havent ran a compression test. However the engine doesnt sound or feel like it has a completely dead cylinder when it decides to run right. Ive turned the motor over by hand a few times and there no noticeable issues. On occasion it will idle perfect so im GUESSING my compression is ok. Im probably going to go buy a tester if i get get it figured out real quick. An O2 sensor wont do this. Ive ran the same truck without an O2 hooked up a while back with no detrimental effects. Again i dont have anything to check vacuum, but i can pull of a line and it does pull a good amount of vacuum judging by ear. (talk about precision right?).
And ive check the injectors. they both sray fuel as they should. Probably the only thing i like about TBI is i can see the fuel spraying.

[manicmechanix]

Originally Posted by roadxing

. Im probably going to go buy a tester if i get get it figured out real quick. An O2 sensor wont do this. Ive ran the same truck without an O2 hooked up a while back with no detrimental effects.

I don't think it's the O2 sensor either, but there's a difference between unplugging it and having one plugged in that isn't switching right. With it unplugged it goes into closed loop. Which reminds me does it run rough cold too or even at WOT (closed loop)?

Again i dont have anything to check vacuum, but i can pull of a line and it does pull a good amount of vacuum judging by ear. (talk about precision right?).
And ive check the injectors. they both sray fuel as they should. Probably the only thing i like about TBI is i can see the fuel spraying.

OK but you actually need to see what the fuel pressure is. Looking at the fuel spray dosn't tell you enough. You said you replaced the distributor and module with no change right? Other than a fuel supply problem I don't know what it could be. You can rent tools like compression tester and vacuum guages from Advance and Autozone. Without diagnostic tools there's really no way to tell.