I have a 97 f-150 flareside with a 4.6L. I recently blew the number on plug out. I used the helicoil to fix it and it ran fine for about 30 miles. on the way home form work, the check engine started to flash again. When I checked the code, it was 301 (nubmer one cylinder). I got it home and took the plug out. the helicoil came out with it and and the arm of the plug was busted out (the part you adjust to gap). I found out you have to set the helicoil with a tool. I did that and put in a new plug. I am flopping between a flashing check engiine light and a steady one. 90% of the codes are misfire in cylinder 1 but sometimes I get a 300 code -multiple misfires. can any one point me in right direction

 

You need to get that heli coil out of there or it will just continue to be a problem as it already has. Timesert are the preferred inserts and hold unlike heli coils. Rent or purchase the installation kit and be done with it. What kind of plug did you put in there? And check the plug boot/coil end for damage.

You may need a bigsert from timesert. I would guess so considering you have the heli coil in there.

 

There are only 2 approved inserts for Triton V8's - Timesert or Lock N Stitch. Helicoils DO NOT WORK.

 

Did you replace the no 1 plug wire?

 

Misfire 'condition' is detected by the crank sensor measuring rotation time from the time the coil is fired.
If the rotation time goes too long as "compared" to the rest of the cylinders averages recorded in a table, it is set as a misfire after so many times.
The misfire condition, done this way, is detected for any cause, not just plug, or wire.
Any cause that interferes with full combustion pressure will be sensed even a lack of fuel, valve sealing, head gasket, coil shorted or open, plug wire, plug, boot, ring seal, thread leakage, moisture in the plug well etc.
The only time a misfire is electrically detected is for codes 35x for coil primary winding trouble.
This code involves the coil or it's circuit to the PCM or the PCM coil driver.
Otherwise normal misfires are set as 30x codes and recorded by individual misfire monitors looked at in diagnostic mode 6, test 53, as viewed on a Scanner.
Do the job with the proper tools and insert and it should work out.
Good luck..