My car is running kind of flaky of late. It seems whenever I try to keep a steady speed, no matter what the speed, it jerks a lot...kind like I got some bad gas or something. My fuel filter is new and I ran octane booster with the same 93 octane I always run. It doesn't do it when I get into it, and it doesn't do it when I take my foot off the gas. Could this be fuel pump? TPS?

 

Fred,

The fuel pump is a possibility. That's pretty easy to check with a fuel pressure gauge. It's also possible you have an ignition problem, or a flow problem with the fuel injectors.

I'd lean toward the injectors since the "missing" doesn't apparently happen except at part-throttle cruise. On decelleration, the fuel pulses are very short and little fuel is delivered, and at WOT the fuel pulses are very long, so even an injector with restriced flow would deliver some fuel to the cylinder. An ignition miss usually gets worse under heavy acceleration, and a failing fuel pump or clogging filter would tend to do the same kind of thing, falling short when fuel demand is the highest.

Regardless, you still need to verify a few things before you decide to replace anything. Check the ignition system, and if you haven't tuned up for a while this would be a good time. Do a quick compression test to verify that the engine is in good mechanical condition. Test fuel pressure to verify a good pump and filter. If all those are in good order, perform a power balance test with the injectors. Without a good ignition and compression, the power balance test is meaningless.