Sporadic Sputtering and misfire codes

J

jbeazell

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Hello all,

I've had sporadic misfires for the last year or so, which are getting worse. It started after I changed the spark plugs. I installed AC Delco Copper 41-601 plugs. After this, I noticed the slight misfires, and a rougher idle. The misfire only happens under about 2/3rds throttle and doesn't really sputter until the engine is at around 3k RPMs.

To troubleshoot, I move the spark plug to #6, the spark plug wire to #5, and swapped the coil pack for 3/6 with 4/1. The misfire is still there, and it still exhibits the same behavior, but now it is on #6. I then moved the spark plug (originally from #3, now in #6) into #4. The misfire stayed on #6.

I'm thinking that this leaves me with a bad ignition module. It has the same slot/spot for both #3 and #6.

Does this make sense? Is it possible that this is a wiring problem to the ignition module?

thanks !!!!!

You guys rock, BTW :)

-Jason
 
what year Montana do you have and what size v6?
 
Hello !
I earlier installed spark plugs AC Delco 41-601 and AC Delco 41-979.
My engine was running very poorly.
Now I set the NGK. The engine is running smoothly
______________________________
 
first things first, what gap did you set the spark plugs to?
Have you rechecked all the spark plugs to see if you cracked any of the plugs?

the spark plug wires are easy to damage as well.

either the plugs or wires or both would be my first suspicion.

these coils put out a lot of energy which seeks it shortest path to ground.

with this in mind if you have any one of the cylinders with higher resistance than the others from damaged wires or cracked plugs the high voltage could short out on or near the coils and Ignition module potentially causing damage to the module.

at this point I would suggest double check your work replace the plugs and wires if they at all seem suspect. making sure to properly gap the new plugs and put dielectric silicone-compound in each spark plug wire and coil boot.

Then clear the codes and run the car to see if the misfire still exists.

With high voltage taking the shorter path to ground it is not uncommon for the computer to play musical misfire codes.

once you have done all of this and you are still experiencing a rough idle and codes for misfire.

double check any and all vacuum lines for leaks.if none found

You have to start with the very beginning of the diagnostic flow chart found in the factory service manual.

This means checking everything from compression, slack timing chain, fuel pressure injector spray pattern, checking for carbon that may have broken loose in the cylinders. you may have to break out a DVOM digital volt ohm meter and check the coils and ignition module etc,

Let me know once your done rechecking all the ignition system tune up parts and we will go from there.
 
sergeimoskva said:
Hello !
I earlier installed spark plugs AC Delco 41-601 and AC Delco 41-979.
My engine was running very poorly.
Now I set the NGK. The engine is running smoothly
Click to expand...

thank you greatly for the advise. I changed over to NGK 3403 #TR55GP @ a .60 gap, along with new wires, and things are smooth again. No more misfires.

thanks !!
 
From what I can tell this is the original plug used in your vehicle which is a platinum plug

http://www.napaonline.com/Catalog/C...-Plug-Double-Platinum/_/R-AC_41979_0508962949

The NGK is also Platinum

swapping out the plugs back to platinum shouldn't have made that much of a difference,

My guess is one or more of the plug wires were damaged during the tune up.

But who knows for sure since you did the plugs and wires in one step.
 
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