Hey I am new here and new to the Ford Truck world figured I would buy something different and I am not having the best of luck! I purchased a 1997 f150 ext cab 4.6 v8 and it is not running the best I ran a code scan and it came up coil pack b was bad... I changed coil pack b and it still has a miss with same problem... The speedometer is not working (small bounce 5 mph to 0 mph ) this truck doesn't seem to have enough power to pull its own weight.. Where do I start? Also it has 120,000 miles

 

how many miles? probably tune up time. for the speedo i'd change the speed sensor on top of the rear differential. if that doesnt fix it i'd say its a gauge issue.

 

New Motorcraft spark plugs and spark plug wires would be a good start. Then play with the coil packs.

 

I changed plugs wires ect... and new coil pack I am getting good fire but the truck goes about 30 mph and its like its all it has... There is no miss or anything it has me puzzled I have always worked on cars and even built a few engines I thought this might be a ecu bad any other IDEAS??? THANKS FOR ANY HELP IN ADVANCE

 

Hopfully you put dielectrice grease on the spark plug boots with Motorcraft plugs only. Next you need to fix the speedo issue. The computer needs this info for power control. Next you need to clean the intake and throttle valve with carb cleaner. Then clean the mass air sensor with contact cleaner (not carb cleaner). New air filter if needed. Reset the computer and drive for a week normal. This will allow the computer to reset. If you still have issues then go from there it will give you a good starting point. I just sold my 97 with 265000 miles and it still would chirp the tires in second. with no mods or programs.

 

4.6 l motors are very picky about plug wires; replace only with Motorcraft ones. I replaced my coil packs with Accel ones and they seem to work OK.

Clean TB as advised and MAF wire with approved cleaner.

Also: with your low power issue, make sure you change the fuel filter, Clogged filter results in symptoms like yours, too.

Jim

 

Another possibility is clogged cats.

 

could be cats but need a clean base line to start.

 

Thanks for all the help guys! I will try all of the above and report back thanks again.....