98SuburbanLS

I have been beating my brains in on this problem. Read alot of things...watched a few videos and googled till I couldnt reword the problem any other way. This 98 Suburban with 5.7 would just shut off at anytime, anywhere and any distance. Sometimes it would shut down after a mile or two or shut down 20 miles away. Shut down while moving or sitting at a stop light. When it would shut down, turn the key back to off and then it would restart. If you tried to start it without going back to off, then it would just crank over. No start. Tried telling my wife this, but, she just kept turning the key till she destroyed the flywheel, starter and broke the outer starter bolt hole on the block. Dont ask me how she did this. Never seen that happen before on a Chevy block. At 256,000 I would say its done its job and I got another 5.7 to go in. I am in the process of putting the engine in. But, back to the issue. Anyone else had this random shutting off? We can rule out the fuel pump. I thought that was it. Tank, pump and pressure sensor is all new. Complete tune up. All the battery cables and battery has been replaced. Even the cable going over to the fuse box. The only code I had was misfire. So I did the tune up. Replaced the coil and module. Lots of new parts have been put on since I got this thing. Including cam and crank sensors. So you can see why it is driving me crazy. (Wife didnt help things either.)

jfmorris

I would check the grounding everywhere. I've got a 1996 C1500 5.0L, and I know mine is starting to have a few intermittent issues, such as the blower motor recently, that I traced to bad grounding, and I ran some new ground wires in a couple of places. A bad/intermittent ground could cause the vehicle to die if it affects the fuel system, ignition system, ECM or any number of things. Taking the key out after the interruption in the ground path may serve as a reset to the ignition control system.

98SuburbanLS

I know that all the grounds to the engine was good. Since that is out on the ground. I was checking that all around. I havent done any ground checking on the body yet. I had a problem with my blower motor sometimes running and not. Went out totally one day and I replaced the switch. About 2 weeks later it went out again. Thinking I bought a used heater control unit, that might be the problem. Bought a brand new switch and once again worked for a few days and went out. One of the plugs on the back of the control unit was bad and causing contact to be bad on one of the power wires. Ordered a new plug with pigtail. Wired it back up and havent had a problem since. If you have the problem again, check that plug. I think there was 8 or 10 wires in that plug.

jfmorris

Thanks for the tip on the wiring harness. I assume you mean the one to the back of the control module in the middle of the dash? I know in the past those wires have looked kinda sketchy/melty when I replaced the blower switch, which had practically melted. Poor design really to run so much current through those small wires and connectors.

You checked the engine, but check the ground path from the body to the ECM, as well as the connectors in the wiring harness to the ECM. Under my hood is on the drivers side of the engine compartment, next to the under-hood fuse box. If that computer gets a disruption to ground, I am betting it shuts down.

98SuburbanLS

That is the plug I am talking about.

Yeah I got to check all the grounds on the body. Never thought about the ECM grounds causing it to shut off the ECM. That makes alot of sense. I had thought maybe the ECM was going bad at one point. Was about to dig out the extra one I have.

mountainmanjoe

truck is 26 now, so the ignition switch could be worn out.

98SuburbanLS

I have thought about that. I guess alot of my thoughts on that is how cheap things can be. I know some vehicles I have driven across the country that were 70 years old and never had ignition switch problems. But, then 100% of those cars didnt have 256,000 miles on them. This does make sense too. I am going to check this too. Not dismissing this at all. Thanks for the thought.