Truck dies while driving

I have a 95 GMC Sierra 5.7 that dies on me frequently while driving and usually doesnt want to start back up. Doesnt matter if I’m at a light, slowing down or driving at any speed, slow or on the highway. Happens all the time. When it starts to happen It will start idling kind of rough and the second I press the gas the rpms drop and it bogs down and tries to die. Sometimes if I’m lucky itll work itself out and start driving normal only to have it happen again. In the last 8 months I’ve replaced - fuel pump, fuel filter, map sensor, battery, ignition control module, iac valve, throttle position sensor, had throttle body cleaned and rebuilt with new seals, plug wires, And plugs. Distributer cap was replaced a year ago. Truck is very clean and well maintained and only has 100k miles. Anyone have any suggestions? I’m about all out of ideas. This also was not something that happened over night, this happened once and a great while and now it happens multiple times everytime I try to drive it

When an ignition coil gets bad, they will fail when hot and work when cold.

Thanks I may just give that a try next

A bad distributor pick-up coil can cause your problem.,1995,c1500+suburban,5.7l+v8,1302646,ignition,distributor+pickup+coil,7176


Trade it in and don’t mention a word …

The key to solving this is when it stalls out and then won’t start. That’s your golden opportunity. The problem is almost certainly either no fuel or no spark. Carry some starter spray with you, and when this happens spray some into the air intake. If it then starts and runs briefly, then stalls out, you know the problem is fuel, not spark. Likewise if it still won’t start even with starter spray, the problem is most likely no spark. No spark could be caused by a failing crank position sensor. But don’t replace that part on a guess, you may put in a bad one and take out a good one. The first objective is to determine if the problem is spark or fuel.

I know that when it doesnt want to start I can pump the gas once or twice then hold it all the way down and turn the key it will usually start up.

That’s an indication the engine is flooded. Pumping the gas pedal when the engine isn’t running doesn’t actually accomplish anything on electronic fuel injected cars, but when you hold the pedal to floor during cranking that tells the computer you want it to inject less gasoline than during a normal start b/c you think the engine is flooded. Your truck is probably obd I, so you won’t be able to do a fuel trim measurement. But you may have a overly-rich diagnostic code stored in computer memory.

Common causes of overly rich operation or too much fuel in the cylinders, preventing starting

  • misfires
  • leaking injectors
  • faulty coolant temperature sensor
  • Cold-start parameters are being used for warm starts

When it won’t start you could also remove a spark plug and see if the tip is wet with fuel. If it is, confirms something is causing too much fuel to be injected.

Thanks for the info, I used to think that it was cutting out because it wasnt getting fuel but I do think its flooding. It’s just weird because when I drive it it runs, idles and accelerates just like normal, then it just starts cutting out and trying to die. I thought about coolant temp sensor but I hear when it goes you start getting irregular readings on the temp gauge. My temp gauge is always right where it should be though

Not sure how it is configured on your truck, but on my Corolla of similar vintage the sensor for the dashboard temp gauge is different than the one the computer uses to determine air/fuel ratio. Both screw into the coolant jacket, but are separate parts. There’s a third sensor that screws into the coolant jacket that is used for the cold vs warm start function too on the Corolla. There’s another for the radiator fan, now I think about it. There’s coolant temp sensors everywhere on my Corolla. There’s a fifth one, if you count the purge valve vacuum switcher, which also screws into the coolant jacket. On newer engine designs all those sensors are combined into just one.

Okay its worth a try, it’s only like 20 bucks for my truck

The coolant temp sensor for the computer is usually just a simple thermistor. Resistance changes vs temperature. At room temperature the resistance is usually in the 1000 - 2500 ohm range. Since they have no moving parts these are uncommon failure items, but occasionally we hear reports of one failing here.

Well mine is 24 years old lol