As I've stated before I have a '97 Expi 4.6L 4x4, a far cry from my '84 F150 300. I bought the vehicle last October with 109K miles. I took it to the dealer and had the 100K mile overhaul done (plugs, wires, tranny flush, replace all fluids, etc, etc, etc ) The vehicle ran much smoother after that. Since then I've put 15k miles and new set of tires last week. I now sometimes notice a rougher idle.
1- How often should I change plugs ?
2- Does any one have a preference or recomemdation as far as what brand to use?

 

Motorcraft Double Platium plugs seem to run the best. They should last at least 75,000 miles.

 

A lesson learned years ago from my local mechanic when consulting him an a rough idle situation on my '94 4.6L:

"How old are your wires?" Only 10k.

"How old are the plugs?" Only 10k.

"Hmm . . You didn't install Champion plugs, did you?!?"

Yup! :-(

He told me that Champion plugs just don't work all that well with Ford products. With Ford products in particular, always use Ford replacement parts!

'Course there a whole lot of other spark plugs that don't work well with Ford. And even if you knew of ones that did work, what useful purpose could possibly be served by using an aftermarket product, when you can be assured that Ford plugs will *always* work?

I got rid of the Champions; installed the specified Ford plugs, and the problem was solved.

As for how often they should be changed, I would figure somewhere around 50,000 miles even though they are rated for twice that. After examining the plugs on my V10 motorhome with 50,000 miles, they were obviously due for a change. While the gap on the platinum tips were in good shape, and still completely within specs; the plugs had accumulated a tremendous amount of crud. No doubt they could have been cleaned up and placed in service for another 50,000; when considering the meager cost of new plugs -vs- the time and effort it takes to change them; installing new ones seemed to be the most appealing option.

Notwithstanding, that the plugs were replaced in the process of troubleshooting an engine misfire situtation; while I didn't have a problem in replacing that would soon need to be replaced anyway, I didn't want spend a lot of $$$ throwing parts at the engine that didn't need to be replaced, with the faint hope that sooner or later, the problem would be solved.

I can only speculate that with current-day high voltage ignition systems, that plugs might have served flawlessly for another 50,000 miles regardless of the accumulated crud. Also, with a motorhome, where we might be on the road for months at a time, and thousands of miles away from home, I tend to over-service the rig, in an effort to ward off misadventure when I'm most vulnerable.

BTW, the elusive misfire situation on the V10 turned out to be a weak COP.

 

I would assume the Ford dealer used nothing but genuine parts since that service stop cost me full day, so much so that the service manager told me go home and gave me a loaner 'til they got done. So what I look for since these were only replaced 15k miles ago? I've never had a service engine light, and I'm noticing that hesitation alittle bit more at idle. Should I just replace O2 and airflow sensors to be safe?

 

I would check the PCV hose assembly. They are known to crack back where they connect to the intake manifold. I would also clean the MAF.

 

What should I use. CRC electronic cleaner?

 

That would work. Anything that doesn't leave a film. I like brake and parts cleaner myself.

 

I use STP Carb and Throttle Body spray for cleaning MAFs. It's always worked well, so I stick with something I KNOW that works.

 

Thanks guys, I'll let you know after the week end. Hopefully it will improve my gas mileage too.

 

Don't overlook the exhaust gas recirculation (EGR) valve. It is possible for that to malfunction and not be detected in the on board diagnostics. Symptoms may include rough idle, hesitation from idle, odd almost out of time sounding exhaust note and sporadic behavior.