I have a unique problem happening to my F-150 4.6L Supercab, for the past 2 weeks it has been stumbling on acceleration and running rough. I thought it might be the gas because no engine codes were thrown, and added some Heat gas injector cleaner. Then it ran fairly well for about 2 days, then yesterday it started running rough, and threw a code of a misfire on cylinder 4. I changed the fuel filter out, and checked the fuel pressure was 30 psi at idle (low end of fuel pressure). Could it be a fuel injector clogged or no longer working because no codes have been thrown, and usually on a misfire a code is sent almost immediately.
Any help would be appreciated. I have 185,000 miles, and changed the plugs and wires out at 162,000. Is this a sign that a cylinder is going bad?
I was going to pull the plug for the #4 cylinder tonight, and see how it looked.

 

I recommend removing all the plugs, doing a compression test and installing new Motorcraft plugs and coils.

You can either rent a compression tester from your local parts store, or buy one. The Harbur Frought has them in the auto isle.

Good luck.

 

I'd add a couple bottles of Gumout with PEA or Chevron Techron to the gas and see if that helps. You said one bottle of something helped.

 

So I checked the #4 cylinder, and the plug looked fine, and the fuel injector ohms were in spec. Was going to check each fuel injector with a screw driver to listen to them clicking. Also, was going to add some BG 44K, and see how it runs.

 

BG44K is not what it used to be, not worth the money. Use Techron. I'd still recommend a compression test.