I have a 1996 jgc 4.0. It cranks up fine in the morning and when I leave it does fine. But once I hit around 20 to 30 mph it starts surging like it’s running out of gas. If I keep feathering the throttle it levels out and runs perfect at highway speed, but if I slow down or stop it surges again. And levels back out in a few minutes. Check engine light is on and it’s a (o2 high voltage bank one sensor one) I’m stumped changed fuel filter which had rusty gas coming out of it.

 

That O2 sensor code is a huge clue. You've got a classic symptom of a failing fuel pump. It's weak and can't keep up with demand when you first accelerate. The rusty fuel filter confirms you have corrosion in the tank, which is likely what killed the pump.

The surging is it struggling for fuel. Once you're at highway speed the demand is steady and it can barely keep up. Replace the fuel pump and filter, and strongly consider having the fuel tank cleaned or replaced if it's full of rust. That O2 code is probably a side effect of the engine running lean from the lack of fuel.

 

thanks for the info I knew it was a fuel issue, just puzzled me how it isn’t acting up the whole time. I ordered both o2 sensors a fuel pump and filter, and a new tank. When I get paid this weekend I’m buying timing chain kit valve cover gasket and a new exhaust manifold. I’ll let yaw know if the new pump and filter and sensors solve the problem.

 

A new upstream o2 sensor solved it. I went ahead and dropped and replaced the tank, fuel pump, and fuel filter. Runs a hell of a lot better now. Next is a new exhaust manifold and timing chain kit, and distributor.