I have a 1993 F-150, 5.0 (302)

I just done a complete tune up on my truck. I replaced rotor button, cap, plug wires (brand new factory wires) and put in some AutoLite platnium pros. When i first drove the truck after the tuneup it missed really bad if you had it in any kind of pull. Like going up a hill. But the idle and crusing on flat road was perfect and smooth. So I took all the plug wires off and put them back on and the missfire has almosty totally gone away now. But it still misses pretty bad on really steep hills. It kind of feels like it isn't getting any gas but I also put a new fuel filter on and that didn't help. I also put in some new gas to make sure it wasn't bad gas. That didn't help either. I'm thinking that maybe the PLatnium plugs just won't work right in my 1993 If I recall I think some other people have had problems with pre-97s and platniums ? Do you guys think this could be the cause ?

Thanks for your time !

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I've had Autolite platinum plugs in my '93 5.0 for 70000 miles with no problems. In fact my truck used to eat plugs about ever 20000 with standard plugs and the platinums solved that problem.

 

You might still have a wire problem. Be sure to seperate the wires as much as possible. Also, it's not impossible that one of the "new" wires is bad or even a bad plug. I've had both.

Pull the plugs and see if you can see which cylinder(s) is/are missing. The one with problems will be wet with gas or a different color than the others. Then replace that plug...if it still misses, replace the wire.

Neal

 

I am a real nit picker when it comes to my vehicles, and I tend to try different things to see what kind of results I will have. In four years, I have tried six different types of spark plugs in my 4.9L. It's not that they needed to be replaced, I was just curious. It also gives me a good reference to go on when recommending different plugs to my customers. I tried Autolite Platinums, and with them the truck ran the worst. I know that many people swear by them, so perhaps I got a bad set. What did work the best were Champion Truck plugs. This really surprised me because I have never been very fond of Champion in the past. As far as whether or not this will cure your trucks ills, the only way to find out is to try different plugs and see for your self. Tenderpaw has a very good point: make sure the wires are seperated. Ultimately, you don't want any two wires touching each other. You can get some cheap plug wire seperators at most auto parts stores. If that doesn't work, try what Nomo suggested and at least isolate which cylinder it is that is giving you problems. I think it sounds like you are developing a cross fire condition from having your wires too close together, but it's really hard to say without seeing and hearing your truck in person.
Take care,
-Chris

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'95 Eddie Bauer F-150 SC & '64 Falcon/Ranchero
-------------------------------------
Are you A.S.E. Certified ? If so, ask me about
iATN...the best tool you'll ever have ! ! And it's
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BMW325: I've heard from several different people that you should seperate wires. In other words don't put them together. Its kinda tough to run them under the upper intake, but there are special holders that you can buy to keep them seperated.

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Thanks!

1993 F-150 302/e4od/355 Limited slip. dual exhuast w/o mufflers,2 1/4" pipes with Echo Tips, headers, accel plugs/wires(8.6mm)/rotor/cap, hypertech powermodule, NEED INFO ON BLASTER COILS Alpine cd player and Pioneer speakers.(Front, need info on rears)

1989 F-150 XLT 4x4 302/aod true duals with turbo mufflers, 30X9.50" wild country tires, 3:55 gears w/LS(want after market LS for front)

 

Ok guys I went and bought all new factory motorcraft plus from my dealer. Got home took the old ones out and seven of them looked perfect and one of them was black with gas, so i put all the new plugs in thinking maybe I had a bad plug. I put all the plugs in and went for a drive and the same miss was there. So I went back home took the plug out and it was once again black and gas soaked. So I put a new plug wire on that plug and went for a drive. Same thing again and the plug was the same when I got home. I took the distributor cap off and checked out the rotor button and the inside of the cap looks fine. I can't figure out what the heck is wrong with this thing. I took the plug wire and stuck it just barley on the plug and started the engine I could hear it arcing and firing. So I took that wire totally off and started the truck and it still ran but had a bad miss (of course) so aparantly the plug is firing when it is idling because the idle is just a smooth as new. But as soon as it gets in a pull (Say 60mph 1500RPM in OverDrive) then it will start missing. I am totally stumped !

 

Which cylinder is miss firing? Make sure the 7 and 8 plug wires are not next to each other. I cannot confirm or deny this, but most Ford mechanics I have talked swear that since the 7 and 8 cylinders fire consecutively, having the two plug wires next to each other can cause the very problem your describing.

 

Hey BWM325- mtucker is right. I am convinced that this is your problem. #7 & #8 are often problems. #2 & #4 also have a similar problem. You must make sure that these wires are completely seperated. I have known cases where even using seperators wasn't enough. One guy with I talk tech with in Conn. had a '92 F-150/5.0 with the exact same problem. He had to reroute the wires so that in his harness the #5 & #6 were inbetween #7 & #8, and he put #1 & #3 between #2 & #4. That finally solved his problem.
Take care,
-Chris

------------------
'95 Eddie Bauer F-150 SC & '64 Falcon/Ranchero
-------------------------------------
Are you A.S.E. Certified ? If so, ask me about
iATN...the best tool you'll ever have ! ! And it's
free

 

For future reference: I learned a long time ago in high school that you replace one wire at a time. You take one wire off and route the replacement in the exact same place. Truthfully, the reason I followed that advice was because I had no idea which cylinder fired next. Never knew until a few years later that there was something called cross firing.

 

Ok this very well could be my problem. Because the way the wires are right now I have 4 on each side and they are all 4 right next to each other tied (not tight at all and not on top of each other) with a nylon wire tie. I will have to check this out in the morning. The cylinder that is miss firing is the front cylinder on the drivers side closest to the radiator. So which number is this ? I appriciate everyones help. This is pretty much my first American vehicle so I'm still learning and saving for a 2000 Lightning

Thanks again !

 

That would be #5, which usually does not suffer from crossfire, under normal circumstances, but if you've got them zip tied together, then anything is possible. Try seperating them, again so that no two wires are touching each other anywhere.
Take care,
-Chris

------------------
'95 Eddie Bauer F-150 SC & '64 Falcon/Ranchero
-------------------------------------
Are you A.S.E. Certified ? If so, ask me about
iATN...the best tool you'll ever have ! ! And it's
free