I have replaced all coil packs and spark plugs and still have a miss. Gas mileage has gone to crap and seems a little sluggish. Check engine light won't come on to get a code. I have been told a 100 different things. Truck is 2002 FX4, 5.4. Any help appreciated.

 

be diligent and check for a vacuum leak

 

You could have a plugged injector or inadequate fuel flow. If not done in a while, change the fuel filter. You could also run a can of fuel system cleaner through your next tank of gas. Test the fuel pressure to determine if your fuel pump is going bad. and, yes, as noted previously, check for vacuum leaks.

 

Thanks, I will check

 

I went through a fuel filter, PCV assembly and plugs before mine was right. Check the fuel filter as mentioned below, you'll probably need the tool to remove it as well. Also check for vacuum leaks. My leak was obvious, but you can spray small amounts of carb cleaner to find the leak.

 

It could take a little while for the code to come back on if you cleared it.