02 4.7 95k mi
Had the truck 7yrs. Put on 30k since then. Done all maintenance, repairs, and diagnosis myself.
New radiator, hoses, and flush (bypassed heatercore).
Dealt with oil pressure switch, gauge issue, seafoamed, new pickup tube and pan gasket ran great for last couple years.
New rotors and pads.
New shocks and struts. Rancho S5000 all around.
New ac/heater control. New condenser fan. Recharged.
New rack and pinion. (Shop done)
New tires.
Oil and filter changes. 3K mi, Mobil-1 syn, wix or etc filters.
NGK platinum plugs, until 2k ago Denso iridium plugs. 10-15k

Changed my oil. Haven't been driving as much, filled up over a month ago (26 gal tank). Never run less than 1/3 a tank, always 87 top tier gas. Truck has been sputtering and misfiring since then. Feels like it's running on 5-6 cylinders or out of time. No metal noises or back fires. Threw a couple codes and check engine light. Added seafoam to fuel. Checked codes multiple misfires, couldn't clear them with my blue point scanner, disconnected battery. Pulled plugs, all fine. Codes gone. Drove it sparsely, 10-20 miles ran like crap, stuttering, no new codes. Pulled and replaced oil filter, thought it had bad valve, no change. Had my neighbor use his Snap On scanner to read live data, it still ran like crap. Couldn't see an the issue. Flip flopped a few coil packs, no change. Checked for vacuum leaks, PCV, etc. Inconclusive. Thought head gasket, did gas test in coolant tank, nothing. Decided to do a cylinder compression test, all held at 120-125psi. Thought it was a coil pack (cop) or bad injector (original), ordered and replaced all of them. Per OEM #. Still ran bad, no codes. Checked fuel pressure, 50psi at fuel rail. Tried another cheap scan tool, no new codes or data. Drove 20-30 miles still idling wrong. Down to 1/4 tank Friday, put 5 gal of premium 92 octane in it. Cleaned the throttle body today. Pulled out IACV, TPS, and Air Temp sensor first. Cleaned with MAF cleaner. Let dry for several hours. Reassembled and went for a 1 mile drive before dark. Same bumpy idle.
Any thoughts or ideas?
Don't want to have to pay dealer for a scan, but I think it needs live data tracking or a more intensive computer analysis.
Buddy thinks I have a computer or harness issue that coils or injectors aren't firing properly.
I'm wondering if it's fuel pump, regulator, screen problem. I think it's running rich on some, lean on others, but can't tell. No excessive smoke. No visual or auditory changes, and still no error codes.
Kinda funny there's not many 4.7's from this time on the road. I've done about all I can to try to keep it there 20 years later. Open to any and all advice! Thank you!

 

Try putting in some plain ol' copper plugs. These engine are notorious for not liking the rare earth fellers.

 

Thanks for the tip. Any personal preference between Autolite, NGK, or Champion. I want to say this truck had platinums in it, (original, maybe?) when I got it. Always have bought best parts I could afford for each project. Last set were Autolite iridium I got for same price of copper and these Denso iridiums might be too hot for this tired motor. Battery is 2 yrs old 12 volts, engine off, and 14+ running. I'll have them test it at the store right now. Might as well ohm out all the new coil packs too, see if they match, and check a few more things. Appreciate the help.

 

Autolites or NGK would be my perferance. Too many bad experiences with Champions.

 

Copy, sold. Autolite it is. (NGK's are #1 plug for most IMHO) Thank you, again. Idk, I have some faint memory of Champions breaking at the nut or something. Not ever purchased them.

 

I used to do equipment maintenance for a tree company, and our chipper had an industrial 318 on it..... carbed, manual everything.... if one of the kids flooded it out trying to start it, that was it, you were done till you changed the plugs..... I kept a couple sets in the toolbox on the chipper, for just such an occasion.

 

Glad I buttoned everything up yesterday. 😅 Got over an inch of snow last night. Idle does seem better, for a short 5 mile trip . Truck hesitated to start when up to temperature after going in the grocery store. No codes. Ignition switch, some underlying electrical gremlins, the testing goes on... Add some more fuel tomorrow and maybe check plugs, wiring, and electric connectors this weekend.

 

New copper plugs seem great, put about 20 miles on. Rough idle smooth, back to previous rpms 600 +/- once it settles down. However it takes two tries and some gas pedal pumping to start. Still no error codes. Reset the gauges when I did the plugs. Voltages good for battery and alternator. Noticed that the accessory position isn't working on the ignition, (don't use, yet another mystery.) Little bit of slop in key, original. 🤔 Ordered a new ignition switch (Standard motor prod, and doorman cylinder rekey cylinder). Rockauto was the only place that had both, and OEM stuff only on e-bay from junkyards and looked suspect. Replace those hopefully by Tuesday, test some more. Maybe some highway miles if all goes well. Everything still fishy, idk. (Could just be me, being apprehensive after chasing my tail for two months since symptoms started.) Maybe do another cylinder compression test.

 

Have you tested fuel pressure??

 

Fuel pressure was 50 psi at pump. Tested before I replaced all injectors and coil packs. (Think those were original ones as well.) Now questioning whether I should have tested with passenger watching gauge while driving, while I could feel motor, steering, etc.