Miss fire but no ses
Thread Starter
TECH Fanatic
Joined: Jun 2006
Posts: 1,220
Likes: 0
From: Nashville, TN
Miss fire but no ses 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?
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.
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.
not under the section with the engine data. The misfire data wont pick up misfires any better than the PCM.
