I have a 91 chevy k1500 5.7l tbi auto 4x4... I bought this truck a couple of months ago with 167,000 miles on it and it ran fine... Now it sputters and seems like its either flooding its self out or missing while driving... If the map sensor is pluged in it will not idle or run properly while driving. If i unplug it it sometimes idles fine but runs like it missing while driving it... I have replaced the plugs, wires, cap, and rotor thinking this will fix the problem. Tested the tps, map sensor, and egr valve and all of the work properly and replaced them thinking that maybe it was human error but still the same problem. Replace the coolant temp. Switch hoping that it was sticking open or closed but that didn,t work either. Pulled the catalytic converter off thinking that maybe it was starting to clog really bad but nothing... Im really confused and thinking about sending it to a shop but don't want to pay the money... Kind of broke... Any ideas or suggestions of any kind would be appreciated... Thank you...

 

Sarge, I'm thinking some of the guy's at the hobby shop, (they do still have the place where you can work on your vehicle??) should have a Snap-On computer you can hook that bi*** up to and do a scan. As a last resort, I'd try the motor pool mechanics. Just thinking outside the box here and hope I didn't confuse you in the process. Once saw a clogged fuel pump filter (in-tank sock) do this same thing too.
Oh yeah, Welcome too.

 

maybe try to check the injectors. sometimes they get clogged and it will make it run like that. my cutlass I used to have did the same thing and that was the problem. hope this helps.

 

Im having the exact same problem on a '93 motorhome with a 454 tbi. It has no power, misfiring, sometimes doesnt start with map sensor plugged in, unplug it and it will start. I checked for ignition and that works on all cylinders, then I checked vacuum at idle and the needle on the gauge was fluctuating from 0 to 20 inches. I think on mine ive got a burnt valve or something. Im gonna buy a compression gauge and check compression on all cylinders. I pulled #6 and 8 spark plugs and found #6 was wet with fuel, and 8 was dry.

I'll let you know what I find out after the test. If you got a vacuum gauge, you should check it, plug it into the intake manifold and it should read about 17 inches at idle steady.

 

So i did a fuel pressure test on the fuel pump last night and when you turn the key on (not running) the pump will go to 3lbs and drop back to 0lbs. With the truck running it only gets 3lbs of pressure. So im going to replace the fuel pump tonight and see what my results are...

 

So I went with my gut instinct and decided to replace the fuel pump and problem solved... every thing is back to normal... thanks to every one for their advice... ooo and by the way gwampa i am a motor pool mechanic....