Hey everyone. I am new here and look forward to all the knowledge that everyone has. I have a 1995 F150 2x4 with a 5.0 engine with 250,000 miles. My problem has been that after the p/u runs about 10 miles, it starts missing out. I had the Ford dealership do a tune up last year and also flush the injectors after it was doing the same thing. They replaced plugs and wires. It finally started missing again a couple months ago again. I looked under the hood after dark, and it looked like a lighting storm was under the hoop. We were planning a vacation so I changed out the wires before we left. It made it to about 500 miles before it started missing again. I took it into the Ford dealership in El Paso and told them what it was doing and that I just changed plug wires on it. They changed the plugs out and said it was good to go. (Plugs that were in it checked out good also) I made it about one mile down the road and it was still doing the same thing. $172.00 later and still have the same problem. I looked under the hood again at night and could see arks(?) down around the plugs. I changed out the wires again, and had the electronic module(?) checked out which check out good, and made it for a while before it started the problem agian. When looking under the hood at night, I still see arks around the plugs and a small one at the coil. The boots are pushed down good on the plugs. Can anyone tell me what my problem is and how I can fix it? Sorry for such a long read, but needed to let you know what all has taken place. Thanks, Bob

 

Generally when you can see arcs down around the plugs, its either a loose connection or the spark plug insulator is cracked.....if you're sure the boots are tight, take out the spark plugs and check the ceramic insulators.....the cracks will be little grey/black lines in the white ceramic, or see if the ceramic is loose altogether (from someone using the wrong socket to put in plugs).......

Also, just because the boots are pushed down on the plugs does not mean that the connector is fixed good onto the plug. Wiggle the wire around while you're pushing down on it until you feel it engage onto the spark plug, there will also be a quiet click sound. If you can just take the connector on and off, then it needs to be crimped down.

This could be causing your miss, but I don't know why it would do it only after warming up, and unless the wire is bad or the connector is completely off, you shouldnt see any arcs coming from your coil (bad coil?).

Anyways, check all that out and see what you're up against. Hopefully someone else will chime in some other info to help ya out.

 

I would start by not going to the dealer any more. Then start on the truck by shortening the plug gap to .035. You clearly have a voltage leakage problem from cheap plug wires. The amount of voltage that is allowed to build in the wire is a function of the plug gap. So by closing the gap you are lowering the amount of voltage in the wire and leasoning the chance of the voltage leaking out. This should do you alot of good, then on to the real problem.

The leaking wires are the real problem, so how to solve that. First a question what kind of plugs? There is no reason to use anything other then cheap Autolites or Motorcrafts (same plug) the more expensive stuff can only benefit you by lasting longer under ideal conditions, but that's not happening is it. So remove any fancy plugs from the questionable list by taking them out and putting in standard cheapos.

Back to the wires, you probably have two things going on, dielectric grease, and cheap wires. Most people and even techs don't understand that dielectric grease is an insulator not a conductor. So they put it on the metal parts that make contact, this is wrong. Dielectric grease should only be used on the boot, to lube it and to seal out moisture. We use special grease for this job because it does NOT conduct the spark. But if it is aplied to the contacts it creates a resisance that the elctricity must find a way around. Next the wires, 99% of the wires on the market SUCK, yes even the Ford ones. There are two things to consider in wires. One, the resistance to flow in the wire, most are between 400 and 600 ohms per foot, this is alot. There are two good brands of wires on the market that are only 50ohms, MSD and my favorite Taylor Wire, the ThunderVolt series. They cost twice as much but I've never killed a set and your motor will thank you. The second thing to consider is keeping the juice in the wire, this more or less is just a function of the diameter of the insulation get a 8mm or better.

So get some cheap plugs, gap them at .035, and get these wires Taylor Cable, Spark Plug Wire Sets - summitracing.com


I know I got a little long winded and maybe a little bossy, but well you asked.

 

Thanks guys, I will try this. Bob