[Steamer98]

I've had a Cylinder #1 miss fire code for the last 3-4 months, truck is running fine with maybe an odd idle once in awhile, but basically runs well.

Shortly after the code I changed the plugs along with 8mm wires, cap/rotor, MSD 8228, and 62mm TB. Code went away for a week or so. but came back, and basically stayed. Still runs well, but also still have the CEL. Codes been cleared a few times but comes back.
Here are the plugs after about 3 months. Left is the #1, center is #2(the rest look the same), right is one of the old plugs(not sure if its #1, but they all looked about the same)


Im not sure what the color of #1 indicates(the problem cylinder), but it looks like #2(and the rest) indicate a lean condition?

Any suggestions? My injectors have about 130k, no leaking, but might be time for replacement?

[severous01]

before you spend 200 bucks on injectors you dont need ( i say that because they almost never fail), check a few things. check fuel at the rail, and before the pressure regulator to determine if it's a pump or regulator issue. check the connector for corrosion and proper resistance at the weatherpack.

[Steamer98]

Thanks severous, although thats a bit over my head. Sadly I dont believe I have the tools for that, nor the knowledge on procedures, but not afraid to learn
If its a pressure/regulation issue, wouldnt that span across the rail?

[severous01]

well, for 20 bucks you can get a pressure guage at your local parts store. that will save you in the future if you have any fuel problems.

very simple to use. remove the plastic cap from the fuel rail. apply guage. read guage after turning key to run position...do it again...read it again.

move guage to the plastic cap pre=regulator. repeat step one.

[Steamer98]

I can do that, thanks.
What values am I looking for? I think my injectors work at 49 pounds.

Thanks again man,

[Lew360]

Doesn't the pre '99 4.0 run a little rich on 1 and 6 just do to the intake manifold design? I'm pretty sure I read that somewhere.

[severous01]

anywhere between 40 and 55psi is fine. any less than about 40 and you'll run the injectors low, and any more and you'll run rich.

[BrunoS]

#1 plug looks like it is running lean or too hot.

try all new NGK or autolite regular plugs.

also check fuel filter and change if possible.

[Steamer98]

Cool thank you,
I'm concerned that one plug is not like the others, I was a bit surprised to see the condition of #1 when I pulled the plugs today to have a look. These test seem to suggest I would have problems across the entire rail if I failed them?

[BrunoS]

#1 pitcture suggests problems with injector plugged off or bad spark plug. your "rail" is fine.

I would suggest change out #1 plug, and top off with a tank of gas and a $10 bottle of techron.

clear out computer and drive it for a week. at the end of week, pull plug. that should take care of any plugging problems.

try that first.

after that, post back and let us know.

good pics, and good to know that cylinders 2-6 look very normal.

[Steamer98]

Hey Bruno, thanks

Actually I've already have done that. When the CEL came on I had the code read, then did the plugs, wires and the other items I mentioned along with 4 bottles of Tecron(on sale, buy one get one free) 2 bottles of Lucas injector cleaner, and some seafoam. Cleared the code for each treatment, either buy pulling the bat cable, or an actual code reader at AutoZone clearing it, but it would come back.

The current #1 has probably been under this condition the longest as it was only a few days of a CEL before I pulled the old plugs and replaced them. Those plugs really didnt hint at a problem because it had only been a few days. The #1 plug pictured is only 3 months old, and suggests I do have a problem.

[Steamer98]

Bump, any other thoughts, or suggestions?

[severous01]

pull injector and check screen. if it's clean, replace injector...if it's dirty, then clean it.

[Steamer98]

Yeah I've been researching that procedure currently. I am also thinking I will move it to #2 to see if the problem follows.

[Steamer98]

Did a compression test today.
Removed all plugs, coil wire, unplugged injector wiring.
#1 125
#2 155
#3 170
#4 170
#5 165
#6 160
The first test was only half warm, so I did it again after getting to full temp.
#1 125
#2 150
#3 165
#4 170
#5 165
#6 155

Seems #1 is a bit below specs... Any thoughts?

TIA
Tom