I have a ‘98 Blazer LT 4.3, sitting at 284k miles. Over the course of a week, I’ve replaced the plugs, air filter, EGR valve, gotten a new CAT and muffler installed. Two days ago, I was driving on the highway and noticed that my RPMs dipped ~200-300 and I felt a huge “bog” on the vehicle. I have it gas, and it fine; let off the gas, and the RPMs nearly bottomed our causing the vehicle to jump like a manual when the clutch isn’t let out correctly.

after this happened, I had my mechanic buddy strap it up to a scanner and it showed a misfire in 1&5. He adjusted the distributor, and checked the plug wires. Shut key off, then cranked it and the misfire codes were gone.

ran fine for ten minutes, then the same issue started again, this time, causing the truck to completely die. I got it cranked back up, but had to hold the throttle open to get it to stay running.

I pulled into my driveway after punching the throttle, and the RPMs steadied out. I sat there for 10-15 minutes as it idled and never once had an issue. Began driving again, same issues occurred.

what the heck do I need to do?

 

anyone????

 

Check fuel pump pressure

 

Ditto.

Sounds like the pump is on it's way out. Low fuel pressure will cause multiple cylinder misfires. Being that yours is pre-multi port spider injector, it uses the popet valve style spider. Once the fuel pressure starts to drop, those two cylinders that are showing as misfires might just be the first two that were the most susceptible to not injecting fuel into the cylinders. But chances are it's more than just those two...

 

Thank you guys. How difficult is it to replace one DIY?

 

and for clarification, are you saying it’s likely both the pump AND the spider?

 

No, he's saying the old style poppet injectors are more sensitive to low fuel pressure.

Remove fuel tank to replace fuel pump. Careful not to break plastic fittings on lines when removing tank.

First make sure it has a fuel pump problem by checking fuel pressure.

 

On top of checking fuel pressure off the schrader valve on the back of the block, make sure you do a leak-down test too. Fuel pressure can be good, but you want to make sure it will hold that pressure for 10 mins or so after shut-off and not immediately drop.