I'm getting a slight misfire when going uphill. It does not set off the cel. Going to start by changing the spark plugs. Original plugs where changed out at 82,000 miles. Truck now has 127,000. Being that these are not the original plugs- do I have anything to worry about when changing them? If this does not help will be changing out all COP's next. Four days for Motorcraft SP-515 to come from Rockauto. Any thoughts or suggestions appreciated!

 

Normally there is no problem on the second set coming out, I recall only one guy that had one break. While you're working on it, check the injectors for leakage, clean the MAF and the throttle body if you haven't.

 

How hard is it to check the injectors?

 

Lift the fuel rail, keeping the injectors in it. Put paper under the injectors and turn the key on.

 

I have the SAME exact problem. Let me know what you find out.

 

why does the second set come out without breaking and the first does.

 

In short, it does not.

Given the same mileage delta between changes, a similar amount of carbon buildup will occur. Hence the same risks exist.

However, IF the feller doing the work used hi-temp nickel A/S, AND did not wait more than ~60K, AND used SP515's, then it's entirely possible the risk is reduced. Reduced - NOT eliminated.

That being said, if you just go and use pre-inspected Champ 7989's, new boots and R&R every 30-50K, yer risk drops to ZERO.

MGD

 

You might want to check your coil packs I had a couple go bad recently.