08 lnf-So after I got my lightweight flywheel installed I have noticed more misfires than normal. It's only @ idle. Doesn't throw a code but I can see them occurring in real time using the torque pro app. Is there a fix to this via hp tuners. I've read that if you run the a/c @ idle it will fix the issue. Haven't tried yet. Should I be concerned about these misfires harming the engine? Plugs are new delcos .032. new coils. Delco as wellT.I.A.

 

A flywheel install would require a bunch of things to be unplugged and unbolted, maybe do a once over of everything related to the ignition and fuel system that has been touched.

 

Come to think of it. I have changed fuel injector seals last 4th of July. This misfire seems to be most prevalent in cylinder one. I've done compression test & was within spec 155_163-158-162. I'm thinking maybe this misfire is fuel related. Thinking about redoing injector seals. Might just get opels considering I have 180,000 miles on these.

 

the misfire counts will be higher with a lightweight flywheel, and that has to do with how the pcm monitors for misfires. using a high tooth count trigger wheel the pcm can actually detect the acceleration and deceleration of the crankshaft with extreme accuracy. during compression the crank will decelerate until the cylinder fires and combustion forces the piston down, accelerating the crank. the more mass of the rotating assembly the less change in acceleration you have. the pcm is set up to detect misfires based on the stock setup. changing to a lighter flywheel will cause the flywheel to be less effective at smoothing the acceleration/deceleration rates, and the pcm picks that up as a misfire, despite the engine running just fine.

i dont believe you can modify misfire detection in the tune, although i cant say ive looked.

 

Wow. Now that's knowledge. This is what I needed to know. Thank you Sharkey for the lesson

 

Exactly correct Sharkey. Same thing happens with the LS engines when you change cams, lighter flywheel, or smaller torque converter. I tune lots of those.

I checked my Cobalt LSJ file, and you can indeed adjust the misfire tables. You would just max out the area at idle and slightly above with hpt.

I don’t check in here often, but still have my 06 SS/SC that I bought new. Just now approaching 100 k miles.

Ron

 

 

Your’e welcome