I have a 97 f150 with 77,000 miles it has a 4.6 v8. This weekend I was towing my boat and the check engine light came on,the truck started to idle rough . The service shop scanned the codes and it says missfire in cylinder number 4. I came home and replaced the plugs and wires,changed the coil,changed the injector,clean the throttle body ,change the fuel filter,made sure the plugs are gap properly ,clear the error code. The problem is now the truck seems to idle ok sometime occationaly misses ,when you give it. Slow throttle it Rebs up ok but if you step on it fast or put it in drive it seem to have no power and seem to be missing .I drove it around but other error codes or check engine light pops up.

 

1st question, what plugs did you put in it? If they were anything other than Motorcraft that's the first place to start in your troubleshooting.

 

i had put a set of autolite plugs that the dealer said was ok so tommorow i will change them. today i had it in the shop and the machanic spend half the day and could not figure it out . he put the diagnostic tool on it and there is no reading of any error. he replaced the mass air flow sensor and still the same result.

 

When ya did all this did you reboot the computer? you have to disconnect the battery for a few minutes with the lights on to clear it so it will relearn..

 

you need to use the motorcraft plugs! the autolites are not made to ford's specs, and are thus, inferior!

 

they had the code cleared. that is all that is needed.

i agree with the plug issue. nothing but motorcrafts should be in there.

 

I replaced the plugs with motocraft plugs and rebooted the computer and she is running fine.thank you all so much for your help.