My 95 Jimmy with 190km lost almost all power suddenly on the highway today. The check engine light came on and the rpm's started to bonuce around, it was doing 500rpm surges every second or 2 and running terrible

I was able to make it home by babying the throttle and going slow. Once I did make it home, the truck was idleing like normal and would rev up no problem when I was in park. Once I shut it off, the truck would no longer start... However after sitting for about 5 hours it did start and quick test drive around the block seemed normal

I need this truck to drive the half hour to work everyday and I'm terrified to take it back on the highway, where do I begin with looking into what happened ? Is it likely to happen again, or is it possible it was something as simple as an EGR valve?

Any and all insight and help is very appreciated! Thanks everyone

 

That it had to sit before it would restart to me excluded a transmission problem. But to be complete, did it seem to work in all gears?

Assuming there is no problem with the transmission, I guess there could be an issue with the fuel or fuel regulation. I don't know if fuel injectors can fail all at once but I suppose they could. Perhaps a fuel pressure test would be appropriate. But also, I wonder if something like a throttle position sensor might go bad too.

The simplest thing to do would be check for codes and loose connectors.

BTW, these are stabs in the dark. Hopefully someone else can give better ideas.

 

Most problems don't just show up and never appear again. They have a habit of rearing their ugly head again when least expected.
You stated CEL was on so have the codes read and see what there, should give you a place to start. Codes will not show fuel pump or fuel pressure problems so look at the sticky at the top of second gen. page. follow the enclosed steps.
Could be a fuel pump on it's way out and after it cools down it will work and pressures up till it overheats again.

 

The truck seemed to shift through the gears fine and I'm almost positive it was not the transmission.

Also, the fuel pump is new and at most 4-5 months old. Thanks for your replies,.. I will try and get enoughoney together to have the codes pulled. I own an obd I and II but this year is an OBD II. 5 and standard machines won't work on it

 

I took off my EGR valve and cleaned it, and took it for a test drive but it didn't fix the issue..

It is totally gutless when trying to accelerate or depress the pedal to hard... If you baby the throttle it will pick up speed and get up to highway speeds.

Could thia be as simple as a bad fuel filter ? Eve if the filter is only 5 or 6 months old

 

Fuel filter - fuel pump - just because it's new don't mean a thing - regulated fuel pressure is it within specks.
Plugged cat, with engine up to operating temps hows the flow of exhaust hard and steady or a week flow, when throttle is increased does the flow increase.
Spark at spark plug, bright blue and jumps around a 1" to ground or yellow and weak.
Just a few easy things for you to check off the top of my head.
I'm leaning to the cat starting to plug off restricting exhaust flow

 

I am with fuel pump....if a Delco pump was not used as a replacement. Need to check fuel pressure. AutoZone and similar will usually rent a pressure gauge. Who replaced the fuel pump? If a shop did, return to them and have them check the fuel pressure.....ignition ON, engine OFF. However in your case you may need to leave the gauge connected, taped to the hood and go for a drive to see if pressure is dropping after the pump has been running for awhile.

Good luck.