Misfiring

SPF Required

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Welp…. That explains it!

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Clearly long overdue for some new plugs.
 
The ones on the passenger side were definitely worse off than the driver side. The two closest to the fire wall were the worst (I can’t remember the cylinder numbers off the top of my head).

It started misfiring on the ride home last Sunday, and since it has been probably 6 years since I replaced the plugs, I figured it was worth the effort even if it weren’t the plugs. Admittedly, one of the plug wires did feel a bit loose when I went to unplug it, so that very well may have been the cause of the misfiring too.

I was prepared to change out the cap and rotor as well, but since the plugs did the trick, I am going to hold off on that for now and at least have the spares at the ready.
 
Have you ever done a cylinder compression test? I'd want to know why they became so fouled. That's a sign of something not being quite right.
 
All the compression test will "test" is the condition of the top (compression) ring and the valves on that particular cylinder. Not the oil rings under it. BTAIM A good diagnostic for general health, just worry about how the values for each cyl compare to each other. The amount of total compression can relate to altitude and such, too.

Once you get all of the numbers, you can then put a few squirts of motor oil into each cyl and run the test again. The additional oil might get a better seal, sometimes. The few times I did that, it added about "10 psi" to the readings on a 90K 383.

DO get a "flexible drive" compression gauge. One with the flex hose between the screw-in fitting and the gauge itself. MUCH easier to use, from my observations.

Cap and rotor are probably still good, just knock off any corrosion on them with a flat-blade screwedriver tip. Usually all they need unless there might be evidence of "carbon tracks" on the inside of the cap.

MIght want to run some combustion chamber cleaner or fuel system cleaner in the gas tank before changing the rest of the plugs, possibly?

Just some thoughts,
CBODY67
 
I have not. Good suggestion. How would one go about that?
It's a simple gauge you connect to the spark plug hole to check compression, and to a degree, leakdown. The one's with the hose as mentioned above, are the best type. I have a real oldie with a rubber tip you just push and hold against the hole. It's kind of ridiculous, but better than nothing I suppose.
 
when all engines were inliners, that orig type of compression gauge might work decently well. But for V-8s, the flex-drive model is best . . . for any engine.
 
As usual, thank you for the tip and knowledge share. The current cap and rotor look good so I am glad I’ve got the spare in the trunk now.
 
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