severe power loss under acceleration

i have a 95 s-10 4.3 TBI with 156k on it. when i bought the truck a few weeks ago i knew the engine wasn't running quite the way it should but i figured a simple tune up would fix the problem. nope. so far i've cleaned the throttle body, replaced the pcv valve, cap, rotor, plugs, wires, map sensor, thermostat (195) and changed the oil. the problem still persists. when i tromp the throttle it loads up, backfires, and then goes... but if i roll into the gas slowly it doesn't have the fuel loading problem. once i'm accelerating, though, the truck just doesn't have the power it should. I've driven other 4.3 s-tens and i know what that motor should run like. the motor idles smooth as can be and the problem occurs regardless of engine temp. :banghead:

i have a 91 s-10 Blazer 4.3 TBI with 146k on it. when i bought the truck a few weeks ago i knew the engine wasn't running quite the way it should but i figured a simple tune up would fix the problem. nope. so far i've cleaned the throttle body, replaced the pcv valve, cap, rotor, plugs, wires, and changed the oil. the problem still persists. when i tromp the throttle it loads up, backfires, and then goes... but if i roll into the gas slowly it doesn't have the fuel loading problem. once i'm accelerating, though, the truck just doesn't have the power it should. I've driven other 4.3 s-10 Blazers and i know what that motor should run like. the motor idles smooth as can be and the problem occurs regardless of engine temp. http://www.automotiveforums.com/vbulletin/images/icons/icon8.gif

hi hows it goin i have a 91 4.3 tbi which seems to do the same thing and i was wondering what you did to fix yours if you did because i didn't see any replys so i don't konw what the problem is can you help me!!!!!!

check fuel pressure, and check for vacuum leaks.

yeah my truck is still running like i described in my post above... i've even tore down the injector cradle and replaced all the gaskets and o-rings, suspecting a leak was causing my problem but no dice. I have triple checked for vacuum leaks and completely cleaned the throttle body. from what i can see... the fuel pressure regulator is ok, i cleaned it as well and re-installed it. I may try replacing it and see if that helps, i'm also planning on doing a compression test soon. My truck has been rode hard and put away wet for many years before i ever had it so i wouldn't be surprised if a rebuild is in order. i'll post the results of the regulator replacement as soon as i get to it.

95, over fueled, check for a leaking nut kit

I had trouble only under load once, like pushing gas more then a little or climbing hill.

Turned out to be weak spark from coil arcing inside itself putting out weakly.

Also make sure connections at coil are not corroded or dirty.

You've got a high mileage engine. At 156K you really need to find out the overall internal health of the engine, especially since you've just bought it and probably have no idea of how well it's been maintained.... or not. Do a compression check and/or a leak down check; this will give you a good idea of the condition of the valves and the ability of the cylinders to hold compression (rings). This check will also uncover a possible blown head gasket. If you've got a bum cylinder or two, then no amount of money spent on this engine (short of a complete rebuild or a head gasket) will get it to run right.

If the above checks show a reasonably healthly motor, then you might consider swapping out the 02 sensor. This device has a direct input into the mixture control of the engine computer (the backfiring is indicative of a rich mixture..... or a bum valve). Given the fact the engine is running like crap, I would suspect you either have a "Check Engine" light on or at the very least some trouble codes locked in the computer. Might be a good idea to run down to your locla AutoZone and have them do a code dump....they'll do it free. Another possibility is a plugged cat.....

mike

well i can rule out the plugged cat cause there isn't one, but i do get a cel intermittenly. auto zone told me they can't do a code dump on my truck cause it's obdI. smells like bullshit to me. anyways... what's a nut kit? i wanna check that.

its not bs az stuff sucks, they have basic code readers, not diagnostic scan tools... nut kit is the plastic lines going to the injectors, thats all i can tell you, ive been fortunet not to have ever had to do one (ive accualy never worked on a cpi moter, worked on s 10s with a cpi in it, just not engin work)

well i can rule out a nut kit then, i have the z code motor with the throttle body on it.

I Had The Same Problem On My 84 S10. I Changed Out The Fuel Filter, Replaced The Pcv And 02 Sensor And It Runs Like A Spotted Butt Ape Now.

I had a 91 with a 2.5L motor in it but had the EXACT same issue. I tried all kinds of crap and it ended up being the Coil.