Misfire periodic cyl 8 and 3

[LETMGROW]

Originally Posted by catmandoo62

if they are not to difficult to get to swap the 8 and 3 coils with other coils.if the problem moves you have your problem if not move on to other options.

Good advice. The coils aren't difficult to swap around and doing so could save buying unnecessary parts. If no change in the way the engine performs simply leave the coils in their new homes and go onto further diagnosis.
If the issue follows the coils to the new cylinders replace the coils.
I would be very leery of cheap coils. Stay with OEM if you need coils and buy only what you need.
"Buy cheap and you'll buy twice"

[1972VWbus]

If you confirm the (2) coils are indeed bad you can bet the others are not far behind.

[RealNiceTent]

Originally Posted by Trek8288

Cylinder 8 has perodic misses of 8 maximum this then returns to 0

Cylinder 3 has perodic misses 0 2 then returns to 0

All other cylinders show no misses.

These are very minimal misses that are very sparadic.

Engine has 20000 miles, almost nothing

I am wondering what fuel the prior owner used ???

the Generator has substantially more hours on it? may have been used mostly for guest home???

Possible carbon buildup on injectors and valves???

What about Sea Foam?

Trek, I don't remember what the length of the cycle is but the misfire counter you are watching is displayed for number of misfires per cycle. I believe it basically translates to 1000 engine revolutions, so the misfires you are seeing are very insignificant. Since they go away off idle, I don't think you are going to do anything but throw money away chasing them, and they could actually be caused by disturbances in airflow into the cylinder like a bit of gasket protruding into the port flow or anything. All engines have intermittent misfires caused by minor disturbances in fuel and air delivery, I wouldn't worry about the misfire counts until you start seeing large numbers.


Dave

[Trek8288]

Originally Posted by RealNiceTent

Trek, I don't remember what the length of the cycle is but the misfire counter you are watching is displayed for number of misfires per cycle. I believe it basically translates to 1000 engine revolutions, so the misfires you are seeing are very insignificant. Since they go away off idle, I don't think you are going to do anything but throw money away chasing them, and they could actually be caused by disturbances in airflow into the cylinder like a bit of gasket protruding into the port flow or anything. All engines have intermittent misfires caused by minor disturbances in fuel and air delivery, I wouldn't worry about the misfire counts until you start seeing large numbers.


Dave

Thank you.
Here is what I did Sunday;
I exchanged the coils that showed the misfires, (minor insignifcant), with coils that showed no misfires. I ran the Snap On Scanner. At that time I showed NO misfires at all.

Therefore I now must assume that I had NOT snapped in the new Magnum ignition wires to the coils when I installed them :(. I checked everything again.

[catmandoo62]

cool,and best part didn't cost you a dime.

[Full-Timers]

Originally Posted by Trek8288

Thank you.
Here is what I did Sunday;
I exchanged the coils that showed the misfires, (minor insignifcant), with coils that showed no misfires. I ran the Snap On Scanner. At that time I showed NO misfires at all.

Therefore I now must assume that I had NOT snapped in the new Magnum ignition wires to the coils when I installed them :(. I checked everything again.

Yeah But...
Didn't you have the missfire before you installed the new wires?

[Trek8288]

I did swap the coils Sunday. I ran the Scanner on the ECU after the swap. It showed NO mis-fires at all. . This would indicate to me that I had not completely snapped in the wires to the coils.:(.

I checked all the plug wires after the scan.