93 Grand Marquis, 56K miles.

My car sometimes (at highway speeds) stumbles, bucks, loses power and slows down. It acts either like it has a governor and it just jerks slightly and loses power. If you apply more gas it does not go faster and if you floor it it actually goes slower. When this happens it sounds like there is some muffled revving under the hood. If this happens all I can do is let off the gas and very lightly re apply the gas. The other thing it does is sometimes after it bucks or jerks the engine will actually race for a second or two, then buck some more like it is almost trying to shift. This bucking will more often take place on a long incline on the highway. It has also bucked when I am going down a long hill and I take my foot off the gas and start to coast. The only engine code I get is the bank one bank two lean codes. I have replaced the fuel filter, the section of fuel return line that rusted, combustion chamber cleaned (drip @ jiffy lube), new plugs. This is random for it can run great 70 MPH up and down hills on the highway and then struggle to do 50. I am thinking throttle position sensor? I am at a loss here and it is not too safe to have this happen on the highway.

This AM I cleaned the MAF & air temp sensor (both very dirty), then cleaned those two connectors and the connector to the throttle position sensor. I used MAF cleaner and the CRC QD cleaner, then used di-electic grease on them all. Car ran great on a local drive with no hesitation or engine light. I will have to try the highway later on. Keeping fingers crossed.