1997 Ford F150XLT, extended cab power 4WD and a 4.6/4R70. 135,000 miles.

When I stomp on it any time it can't get a downshift, the motor will start to accellerate normally, then when it hits 3200 RPM, the tach actually DROPS back to about 2800-2900, and you can hear the engine do this too. When I put it in second instead of drive, and take off, it does that twice. Once at about 2100 RPM and once at about 3200 RPM. The truck lacks a lot of the power it did when we bought it in 1999 with 75,000 miles. A local mechanic said to hit the MAF with some electronic parts cleaner, and to use Seafoam. Any ideas here? It sounds like something's gonna blow up when it does the little RPM drop trick. I'm a little worried. Oh, and if I catch a downshift or take off in first and let it shift normally, it doesn't hardly ever do this.

Also, a few months ago it had the flashing CEL. I took it in, got it scanned for a misfire on the number 8 cylinder. Replaced the number eight plug, didn't help, so I replaced the wire too. Have since replaced all plugs and wired. Well, since I did that, there's an occasional misfire at idle. Could the two problems be related? The misfire is on misfire every twenty-forty seconds, not common at all, and never happens anywhere but idle as far as I know.

 

sounds like a limp mode thing.. how is the oil pressure. check the ignition wires and coil packs. and do an injector service change the fuel filter.. fuel pump could be cuttin out on it also. or could just be simple MAF needing cleaning

 

Wouldn't limp mode throw a code?
Oil Pressure is strong, not at all like a high mileage truck.
Wires and CPs are new.
Fuel filter is new.
MAF I've cleaned with electronics cleaner, and it SEEMED to help, but it came back in a few drives.

What should I do for the injector service? And should I give a bottle of Seafoam a shot through the vacuum line?

 

Do a search on how to clean the EGR and the throttle body. I'd bet that's where a lot of your problems lie.

 

sounds like a clogged catalytic converter could be wrong though

 

I know when the cat went bad on my Grand Prix GTP, it smelled REALLY bad, like eggs. The truck doesn't have that going on. Could the cat still be clogged? I dunno if the egg smell is a GM thing, or if my car was just a freak. I'll clean the throttlebody and EGR valve later today after I finish with the cam timing on my GP. It's a PITA.