Hi all,


I picked up a really clean 1994 Chevy 2500 with the 5.7 v8 350, 114k miles. I’ve been driving it with no problems as a daily driver the last 10 months. Last month, all of a sudden it wouldn’t start until I tried starting it and turning it over about 3-5 times with continuous pumping of the gas pedal. This problem came about the next day after I filled it with gas after a very low gas tank. Once I got it started and warmed up, it drove ok but was sluggish at takeoff until high speeds and the rough idle and random stalling at stop lights etc. would kick in randomly. I had to two foot drive it to keep it going.

I figured maybe I got bad gas so I put multiple fuel treatments and injector cleaner treatments in it and after I went through almost all the bad gas, I then replaced the fuel filter along with the air filter and have it a round of BG 44k fuel system treatment... it started easier and not as much of a problem but the problem persisted. I still have the rough idle, random stalling, sluggish take off, etc. but there was no rhyme or reason to what is causing it. It did drive better with less two foot driving until it all of a sudden decides to act up.

After this, I then replaced the Idle air control
sensor (original was pretty black and probably sticking) and it started driving a lot better with the new part and the idle was better for about a month with better acceleration and take off initiall like it used to drive when I got it, but now I’m back to this no rhyme or reason random sluggishness, stalling and rough idle and bogging down until warmed up. It’s mostly occurring when trying idling at a stop or when going to park at slow speeds or shifting into reverse to back out of a parking space and then shifting into drive. And unless you ramp up the gas, it will stall if you aren’t giving it the gas pedal. So parking and not shooting into a wall to keep it going from stalling is tricky... driving uphill is difficult and no power at times until I get it up to speed. It’s not throwing any codes or engine lights so I’m now thinking maybe fuel pump issue or I need to turn up the idle but it’s too random and drives fine here and there so makes me think it’s a sensor or something else I don’t have experience to tell... Not sure what to check next since from what I’ve researched, it could be a number of things (the torque converter locking up, the tbi needing a rebuild, map sensor, etc etc)... I’m a bit lost now and trying to pin point it so I thought I’d ask the enthusiasts in case you guys have seen this before since from what I gather, it’s a sorta common occurrence on these older 350 tbi’s and this a my first Chevy so I don’t have much for reference. I was able to capture a video today showing what it’s randomly doing (If it posts to this thread, for some reason it’s but posting but I’ll keep trying).

I hope that it helps and I can chime in more or get another video. After my POS ranger, I’m in love with this truck and
stoked I made the switch...besides being a broke bastard, I’m hoping you guys can help me narrow it down a bit more before I start throwing money at it for parts that might not be necessary.

Cheers!

 

Trying to post video but doesn’t seem to be working

 

here use this
Troubleshooting sensors and how to test

but i must say just a few months ago i had a very similar issue with a 305 tbi, tested the sensors put in new fuel and still had a issue. when it stalled it would only start if you floored the pedal this would enable "Clear flood mode" and it would start. well after killing the battery i swapped it with the one in my 94 4.3 tbi and it started up and slowly started running better and better. charged the old battery and put it back in and she still ran great with no issue. summed it up to a poor battery connection causing the sensors to read false data. so something even like a poor ground will cause the engine to run poor

 

Always frustrating when stuff like this happens to your daily driver.
Sounds like a fuel pump going bad perhaps. I had similar drivability problems on my 93 C1500 5.7 TBI and it turned out to be low fuel pressure. The ECM doesn’t have any knowledge of fuel pressure and when if it’s not right it can cause idle, stalling, and low power problems. In my case, I had replaced the fuel pump the year before with a Duralast pump but it was only running about 8-9 psi when I checked it. I replaced with a ACDelco pump, new filter and had 12 psi and it solved stalling/idle problems and the power returned.

Regardless, in cases like this it’s good to check the basics first - fuel pressure and timing before shotgunning sensors, replacing things. There is a good link here https://www.chevytalk.org/fusionbb/s...php?tid/253427 I’d recommend reading. It’s a bit of a pain to get adapter, gage and check fuel pressure but good to verify it one way or the other before moving on. I’d recommend checking at fuel filter as its easier to free up lines going to engine to get space for adapter. + if problem is fuel pressure, you’ll want to replace fuel filter anyway.
Go luck

 

had a 93 gmc
common issues to look at is ,

low fuel pressure ,clogged fuel filter
distributors are a common issue replaced two on mine .

just for grins i check to see if the egr valve is not stuck .

sabino 56 has good info to start with.

 

Thanks everyone for the good info and speedy replies! I did check the battery and connections to be sure and they all look solid and my battery is still reading 12.6 volts so safe to check that off the list. I’ll look into getting the fuel pump checked and possibly see if I can get ahold of something to check the rpm at idle and see if that needs to be reset or turned up after replacing my IAC. I’ll keep running down the list in the order you guys mentioned and will report back with any new developments...