WhosNXT

On the way home tuesday I noticed the motor twitching at idle, closer to home I was in gas conservation mode an went to 4th at about 40mph and as soon as the clutch was out the motor missed. I down shitfted gassed and no miss. As soon as I went back to low rpms with a load it missed. I waited for the ses it never came. I took it to my local mr goodwrench they told me a clogged fuel filter was the problem. Turns out it was not, during the header install the shop I used had cracked 2 plugs. My question is why did my ses never come on?

foff667

iTrader: (2)

was the ses light turned off? also you can get a code & not set off the ses light...you'd really need to have someone scan it to see whats going on & what the computer is thinking.

DAVESS02

iTrader: (30)

Thats actually more common than you might think. My tuner and I were out yesterday dialing in my tune. My car was missing under load but no ses and according to my tuners computer, it appeared to go into a lean condition but nothing to indicate it was the problem of one cyl. I happen to have a tech II and after plugging it in, I went into the misfire graph and found #2 and a little on #1 misfiring. The threshold for triggering the ses is much less sensitive than the tech II misfire graph. This is pure speculation on my part but I think it may be because the misfires you and I were experiencing were at different crank degrees than a misfire that triggers an ses. In otherwords, our misfires didnt significantly slow the rotation of the crank enough for the code to set. I used to be a service tech for a motorhome repair facility and I saw at least 8-10 8100 gm powered motorhomes with the same problem. A few wouldnt even show up on the tech II misfire graph. BTW, for those of you who have access to a tech II, the misfire graph is under "special functions" -(enter)-"engine output controls"
not under the section with the engine data. The misfire data wont pick up misfires any better than the PCM.