I just recently bought this Jimmy form a friends father. The guy told me that on occasion while going down the road it would die but he could just toss it in neutral and it would crank right back up. He said the problem was very intermitent and sometimes it wouldn't do it for days then other times it would do it 3 times in 10 minutes. He checked the cat and said it was clogged up so he gutted it and it never died again for 2 weeks.

Then I bought the vehicle.

For a week it ran fine no issues. Then I was driving it back from work and it died. There was no odd noise or jerk or anything, the truck just cut off. It steadily got worse and happened more often. It never would do it in the morning on the way to work, but after work it was a nightmare. Anytime during afternoon-early evening it would cut off rather frequently.

Me and my friend started looking at it and we changed the fuel filter, it had a rusty orange look to the fuel. Next day on way to pick wife up form work the truck died multiple times and when i went to crank it back up the lights dimmed and was hard to turn over. Pulled over and the AC compressor had locked up on it.

Had a friend tow the truck back to his garage. I didnt want to spend the money to fix the compressor since I rarely use the AC and I was low on cash. We bought a shorter belt and bypassed it completely. While we were at it we dropped the fuel tank and cleaned it out since there was what we thought was rust in the fuel filter then there is probably junk in the tank. We pulled out what I consider "alot" of trash though I have no idea what is an acceptable amount. We replaced the strainer on the fuel pump since it looked like it needed it.

We went down the road when we were finished and the truck cut off, I put it in neutral and tried to crank it and we heard the clatter from trying to crank an already running vehicle. The truck was "dead but it was still running". When the truck died it wouldnt respond to me giving it gas so I assumed it was shut down.

It was late so he followed me to the gas station and I ran some injector cleaner through it with a full tank of gas incase there was junk still in the injectors or what not. It ran fine all the way home. I left it running in park for a good 30minutes and it didnt fluctuate or anything.

2 days later the truck would act like it was dieing but instead of turning it off and recranking I would just coast and the truck would just pick back up again 15 seconds or so later and I could keep driving.

The problem has gotten worse over the past 4 days or so with nothing new done to the vehicle. The truck dies completely, no more coasting and it come back alive. The truck does it regardless of time day/how or cold outside. If you give it gas and get it over 2k rpm you hear it sputter, lose all power, and try to die. Even driving it while keeping the rpms low it will completely die.

When you turn the switch on you can hear the humming noise from the fuel pump so it is still coming on. It had a new fuel pump put in it 30k miles ago.
The service engine light has just came on but when we plugged it up to a tester it wasnt showing any codes. So I havent been able to pinpoint what the issue is.

Ive been told to check the crank position sensor, but before I start spending even more money on this thing I wanted to see what any ideas were on possible causes for these issues.

Thanks in advance for any ideas.

 

Check the coil wire,
Mine did this as well but less often, until yesterday when it died and stranded me requiring I tow the car home.

Started looking around for obvious things and discovered the coil wire had a wear hole in it and was obviously grounding out.

I taped up the hole in the wire to keep it from shorting and the car fired right up.

Ordered new wires, cap and rotor today.

Car runs better than it has in a while.

 

So it is either losing fuel or spark at those times.....
This has got to be a loose or corroided connection somewhere...

Suggest start cleaning grounds on the engine and frame. Fuel pump relay dropping out possibly?

Wow...good luck with this one.

 

My buddy has made it a personal goal to figure out what is wrong with the vehicle ;P

We replaced the crank position sensor and throttle position sensor based off guesses. Neither have made any noticeable effect. We drove it to a local GM dealer and talked to a tech my buddy knows and he looked at it and was just as stumped as we were. While looking at it we let the car sit and run while in park and it ran fine then instantly cut off. The tech said some Jimmys have an issue with the computer going bad and doing similiar symptoms but the model I have has the computer under the hood and isnt the problem child.

One thing I have noticed is when the truck dies you can still hear the fuel pump running like it should and after it sits off a second it smells like it was flooded to death, so its getting the fuel there its just something wrong with the firing or at least i think thats what is happening.

We made a quick pass under the hood and didnt see any shorts or breaks in the wires anywhere. We will make another pass today and see if we notice anything we may have missed. I had 1 other person mention the coil last night and we are going to check that again today to try and rule it out.

Thanks for the input.

 

Sounds like you elminated fuel being the problem....so it must be spark. Ignition modules love to fail when hot, as do coils...but both usually fail when hot until they cool-down. But something to check. I would say take it and get the module checked, but if it only fails hot, then it is going to check good. Too bad electrical parts cannot be returned or I would say just get another one and try it.

Have you check the coil wire? How is the insulation looking...any breaks in it or anything? Move it around with the engine running and see if anything happens. Just wiggle it, do NOT disconnect it with the engine running or you will feel what 25k volts feels like.

Keep us informed.

 

AutoZone should be able to test both the coil and ICM for you. Be sure they test the ICM enough times to get it hot (~10 times).

 

Ok we have it fixed.

A guy i work with has a 96 Jimmy with a destroyed tranny, so he was willing to let me play frankenstein to figure out what is wrong with mine.

Switched out ICM, ran great until we got down the road and it died lol. So we marked that off our list.

All the wires, modules, ignition coil, sensor, kitchen sink all appeared good. So knowing as little as I do about vehicles decided we were getting nowhere and said we should forget everything we already know about the vehicle.

I had my friend test the fuel pump to make sure it was getting the right pressure. He hooked it up and sure enough it was pumping good pressure. He was checking under the truck when he noticed a small change in the hum of the fuel pump. We decided we should change the fuel pump and see if they change in hum was the fuel pump straining a little.

1 new fuel pump later and no more dieing, knock on wood. Seems the fuel pump was dieing but never went out, it would only get under strain and not keep up enough pressure. When the truck would die the fuel pump would still be running and pumping fuel to a disengaged motor letting us smell the gas leading us to believe it wasnt burning and that was our problem.

I guess sometimes ya dont really know what ya think ya know when it comes to these things.

 

if you smell gas, you should check your FPR too....

 

That sounds like a fuel pump acting up on you. They will act fine for 5, 10 or 15 minutes then go haywire. Luckily mine didn't torture me when it died. It just crapped out all at once so it was obvious what was wrong but on other vehicles I have had them do what yours did to you and it is frustrating as hell.