1999 FORD F-150 CHECK LIGHT WITJH CODE PO304

  • Tiny
  • JAS 21
  • 1999 Ford F-150

Our engine light came on and I put it on my computer and it gave me PO304 cylinder 4 misfire detected what do I need to do to repair this, I'm thinking that this problem occurred because this last month ago I changed the heater core and the hose that is over that injector and cylinder water was leaking from that hose. So what steps do I take to repair this situation.

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Wednesday, October 23rd, 2013 AT 1:15 PM

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  • Tiny
  • CJ MEDEVAC
  • Expert
  • 9,247 posts

MAKE SURE YOU HAVE CAUGHT UP ON MAINTENANCE. LIKE CHANGING THE SPARK PLUGS ON SCHEDULE. AND PROPERLY GAPPED/ DISTRIBUTOR CAP/ ROTOR BUTTON/ ETC

LOOK AT THE PLUG WIRE. FOR #4 (AND THE OTHERS TOO!) LOOK TO SEE IF IT IS RUBBING ON SOMETHING METAL. IF IT HAS WORN THRU, YOU WILL PROBABLY SEE A "STARBURST" OF GREY, SPLATTERED AROUND THE "ARC" (THIS WILL RESEMBLE A GUNPOWDER BURN) IT IS EZily RUBBED OFF SO GENTLY LOOK AT THE WIRE, AS NOT TO WIPE IT AWAY

IF YOU FIND A SPLATTER SPOT, REPLACE THE WIRE AND OBTAIN SOME 3/8 FUEL OR VACUUM LINE. CUT SMALL SECTIONS OUT OF THE VACUUM LINE AND SPLIT THEM. COVER YOUR SPARK PLUG WIRE(S) WITH THESE "COVERS" ANYWHERE THEY RUB SOMETHING OR COULD POSSIBLY RUB SOMETHING (JUST THE PROBLEM SPOT, NOT THE ENTIRE WIRE!).

NOT TOO LONG AGO MY NIECE'S MUSTANG W/ 3.8L, WAS SKIPPING (FOR QUITE SOME TIME) IT HAD 3 WIRES DOING THIS, AND A FEW OTHERS GETTING THAT WAY.A NEW SET OF WIRES AND MAYBE 10 HOME-MADE COVERS LATER, SHE DOES NOT SKIP ANY MORE

KEEP US UPDATED

THE MEDIC

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Wednesday, October 23rd, 2013 AT 6:38 PM
  • Tiny
  • hmac300
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  • 43,759 posts

Misfires are very hard to diagnose even for a pro. Check plug wire for good spark and compression and maybe resistance on injector which should be 11-18 ohms. Other than that have apro check it out as it can be something entirely different than what you think.

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Thursday, October 24th, 2013 AT 7:52 AM

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