conanthebarbarian

I have an 89 C2500, 5.7L TBI, that's been developing two problems since I got it a month ago. Over the last 2 weeks it's been intermittent, but the last 3 or 4 days it's been nonstop.

At idle the car will start off smoothly, and about half the time it will start dying then surging after about 15-20 seconds, bucking after 20-30 seconds, and most of the time, it dies after this. If at any point I give it some gas or let it move forward on its own, everything runs fine again. If the car is in park, I usually have 2-3 times as long before each phase happens.

Also, at higher speeds (45mph +), the gas pedal starts giving me trouble. At the start of its range it works fine, and if I push it completely forward the car will shoot out, but anything in the middle gives me less power than having it not pushed in at all.

So far I've cleaned the throttle body, the IACV, replaced the air filter, replaced the fuel filter, tested the TPS which passed, visually checked the spark plugs, wires, and cap, and run some techron in the fuel tank.

I'm just wondering if anyone has some suggestions on where to start from here. What should I be checking? The EGR valve or vacuum solenoid? CTS? From my research it seems the fuel pump is a likely cause... The previous owner said he had just replaced it, but I have no way of verifying. He had clearly done a lot of maintenance, and there are a ton of new parts under the hood including a new transmission, drivetrain, u-joints, etc, so I do believe him, but I'm curious what you guys think might be causing this.

I don't have a lot of mechanical know-how, but I can follow instructions pretty darn well and I'm perfectly able to research whatever info needed if you can point me in the right direction

conanthebarbarian

So today I checked the spark plugs. All spark when cranked, no issue. I replaced the two that seemed to have the weakest spark, but no change in my problems.

Any ideas where to go from here? Since I'm getting a good spark at the plugs, can I assume the wires and distributor cap aren't needing to be checked more thoroughly?

conanthebarbarian

So the truck didn't seem to like the bosch ones I stuck in... It was making clicking noises at me at highway speeds. I went ahead and replaced all the spark plugs with delcos like it had, and the noise is gone. I also went ahead and replaced the spark plug wires.

So far no real difference in either problem. Still idles rough and usually stalls if I'm at a stop too long, and the gas pedal is still unresponsive.

Getting an oil change at the moment... I'm pretty sure it's due for one. Maybe by some odd chance the oil filter or low oil could be the cause??

conanthebarbarian

So the problem still exists, and my fuel mileage is really suffering

I fixed a vacuum leak I found, and that helped the accelerator issue a good bit - it's now good enough that I'm not bothered by it. The truck still idles very rough though, and it still stalls out if I let it idle long enough.

Recently though, it's starting to stall out around 15-20mph. It's done it twice to me this last week, a few days apart. I'm really starting to suspect the fuel pump... I don't mind doing that if it'll fix the issues, but can anyone more mechanically inclined at least tell me I'm on the right track? It'll only run me $60 for a new pump and strainer, though it'll take me a decent while to do the job, but I don't want to keep replacing $50ish parts just taking stabs at the problem.

Any chance this could be ignition related? Maybe the timing chain?

mutt bridges

i just bought a 95 blazer and it skips a little but i give it gas and it runs good does any one have any ides

playboy

i had the same problems.. idles like it wants to die. give it gas all good.. adjusted idle cable. mine had staggard holes each a tiny bit apart. put it on one more up (makin it tighter) it was as if i was giving it the slightest bit of gas for it to purr nicely. put it one more further it sounded like it was on speed. so fixed my issue.. or did it compinsate and mask the problem?????

Zachwooten

i have same problem on 94 burban 5.7 350 i have isolated my problem i unplug the map sensor an the idle surge/die problem goes away but i had just replaced this so my next stab is the ecm or computer they have resistors in them that crud up after time so if you check an any have a white crust on them solder in some new ones an it should fix it im headed over to work on mine now so i will let you know what i find an post later tonite sorry if this doesent help you

TRUCKSTUFF

So I had the same problem in one of my trucks and I fixed everything possible and it would still idle and stall. I didnt even think to check the battery. When I took the truck to the dealership they informed me the battery was good when doing a full circle inspection. I just couldnt wrap my head around the fact that I have fixed everything imaginable and still the problem persisted. So I removed the battery myself and took it to a local auto repair facility. They actually deemed the battery to be defective. The manufacture thought the battery was okay because it was tested when the truck was off. But when you try powering the truck it may be too much power for the battery to handle and thats where the idling and the stalling will incur. Since I have changed the battery there has been no idling or stalling. Hope this may help for those of you experiencing issues.