Long story short, been fighting the occasional ping/rattle on the truck for a long time. Was a 95 day and while pulling my trailer I started hearing spark knock for a split second while I accelerated from a stop. It does it in neutral and drive. Gauge does not indicate overheating (warm but not bad). Haven't checked plugs for awhile, fuel pressure is in spec. I drove with the SPOUT disconnected and it seemed somewhat better but it still does it. Truck runs smooth still. Checked codes and got 634 which I presume is unrelated (mlps code). Overall, I'm stumped. Really hoping it will hold together until I get it fixed but what should I be checking?

 

Pull the plugs, look for signs of a lean cylinder. Could be an injector is not spraying very well from being clogged. If it pings at base timing, something is wrong.

 

"Lean" would show as whiteish on the plug tips?

 

Most plugs will show a brown to grayish-tan color when the air/fuel mixture is correct. White and/or melted electrodes are indications of lean and/or pre-ignition.

 

The stock plug is a SP450 or ASF-42C-F4 is there a 'cooler' plug that would still work? Haven't pulled them yet but I leave like to know if there's a cooler Mitircraft plug that would still work.

 

No reason to go cooler IMHO. That's a band-aid fix.

 

Ok. Will report back after I check plugs

 

Pulled a plug from #1 and #5 ... #1 isn't that bad but #5 is white along the back curve of the tip. Electrodes are rounded. No sign of oil being burned.

 

So Cyl# 5 has signs of being lean. How old are the plugs? mileage and age....

Now you need to inspect plugs 2,3,4 and 6,7,8

 

I'll check the others when time allows. They are all 2 years old or so, hasn't been more than 20,000 miles.

 

If one or more electrodes are worn more than the others that is another sign of a cylinder running lean.

 

Yeah that sounds about right ... But dang like I said it hasn't been more than 20-30k on these plugs. Best way to figure out how/why some are lean?

 

Pull the injectors and take a look. Some have posted how they rigged up a 9V battery to energize an injector. Use a bottle filled with cleaner and an adapter to fit over the top of the injector, squeeze the bottle while activating the injector. Watch the pattern. Or send them off to be cleaned and tested. Or do it yourself.

 

The injectors have a screen in them that can be cleaned or replaced as well....

 

Well, I put in some ASF32 plugs (SP415A) which are a heat range lower than what is specified. I didn't have the SP450A available at the time ... So it runs about the same but I swear the tail pipe is making my eyes water, nose burns like it's running rich ... Could being one range colder on plugs cause this? Don't think it was doing this before. If so I'll order the specified plug.