2002 f-150 4.6 missing under load. runs smooth until load increases doesnt show any codes

 

Could be...
1. Bad fuel
2. Fuel filter
3. Plugs /wires/COPS

 

Describe the miss load under normal acceleration. Know what I mean ? No stabbing the pedal. Accelerate normally to 45 mph. After achieving, keep accelerating normally. What happens after 45 mph @ that particular load?

 

runs fine under normal acceleration. misses when starting up hill in overdrive smooths out as soon as it downshifts

 

That's what I was after. It's a coil.

You can try forcing a blinking cell by running it hard enough to increase the misfire count. A blinking cell logs the misfiring cylinder into the KAM (Keep Alive Memory).

If you can't get the count to increase enough, then your CEL will not blink and log DTC.

The only cheap out then is to purchase a set of new coils. I suggest Visteon coils from an eBay seller.

Otherwise, you may be pulling your hair out trying to get past this.

 

thanks a million jbrew.I thought the same just wanted to hear it from a pro

 

How many miles on the spark plugs, and what brand are they?

 

tried plugs and boots first i bought motorcraft plugs

 

Did you use dielectric grease in the boots?

Coils if you need them:

One: http://www.ebay.com/itm/New-Ford-Vis...c84a5e&vxp=mtr

Set: http://www.ebay.com/itm/New-Visteon-...3989cc&vxp=mtr

 

They're still out there I see, -and cheap! I should at least grab one set. Should go after a couple sets. One for the 04 and the other for the 98. It might be a "when they're gone, they're gone" deal. I'm not sure if they're still in production. That would be great if they are.

 

Glad I saw this thread, mine is doing the same thing. I'll have to pick up some of those coils and change mine out

 

My 00 5.4 is doing the same thing! She stutters/misses when you start start to accelerate, and then once you are moving it doesn't seem as bad. Then once it shifts into a higher gear you can still kind of feel it there when you place her under load again. No codes or blinking cel.

I just replaced the fuel filter, got seafoam in the tank and I ran some through the brake booster intake. It's not missing as bad, but it's still there. So I think mine was a combination of a couple things.

I'm going to grab some cops and motorcraft plugs too.

They don't look like fun to change though lol

 

I had same problems with my 98- was just 2 plug wires. I replaced them in the fall and it ran great all winter. Last Sunday was our first warm day so I swapped the rest.

I got a set of Motorcrafts at Ford for 200$.

Might be a good idea to replace them too.

 

The 5.4 and 2000+ 4.6 doesn't have plug wires.

You overpaid for those Motorcraft wires, rockauto.com sells them considerably cheaper.