deanshark

This is weird but it feels like it is running out of gas so I'm 90% sure it's fuel related. My '93 LS 126K will drive perfect with plenty of get up and go, or cruising under 40 MPH. If I'm at a steady speed as soon as I hit 40 - 41 it will start to buck and jump. When I hit 46 -47 MPH it will go back to normal. When I accelerate it's fine. I've done alot of searching the past couple days but can't find anything useful. I'm just looking for ideas right now b/c it doesn't bother me that much, I just don't drive in the 40s. I'm wondering if it could be the fuel filter, injectors, or pump. I haven't pulled any codes b/c the light is on for other reasons. (AFM unplugged) Any ideas?

I was just thinking, could this be the TPS? I'll pull the codes later when it warms up a couple degrees and post it afterwards.

91LS400vgb

Throttle Position Sensor is what immediately comes to mind. It's very easy to check with a multi-meter. Here is a page from the manual that might help.

deanshark

Thanks, I'll check the TPS when I get a chance sometime next week. I haven't had a chance to pull codes yet but, like I said, it doesn't bother me much. Thanks for that page. I have a manual but it's in storage right now so this page will help.

hobojoe

Had almost the exact same happen to me, at pretty much the exact same speed also. Turned out to be 2 bad spark plugs, replaced them all and hasn't done it since.

deanshark

The plugs are pretty new (about 3K miles) but ya never know, I'll pull them and check those when I get time next week.

I just pulled the codes and all I got was 24 (Intake air temp. sensor signal) and 31 (Air flow meter signal) Those are there b/c I have the AFM unplugged, which I know is bad. It's been like that for a long time (I just keep putting off fixing it) but these new symptoms just popped up about a week ago.

LS400BOY

Happend to me to, i changed my plugs,wires and the stuff in my distributer and worked fine