I have a stock 6.0L Trailblazer SS. Since last summer I get a bucking/surge when I take off from a cold start. The engine can be warm from the morning run and still surge. I think it could be a cold / open loop issue.
I had it tuned and it eliminated the surge until the weather cooled off.
Dealer is no help. When they get it out of their parking lot the issue is over with. No DTC's.
The surge is the worst just before 3K RPM then it quits. (2500-3000RPM) This is light throttle as mashing the throttle to the floor does not surge. Power braking while at the light throttle and keeping it under 3K RPM makes the bucking worse. You can add throttle to a point and add to the surge. This also happens in 2nd gear. After about 2 city blocks this issue is gone until the next startup.
I attach a log of a light surge just before 3K. I think it is going lean just below 3K RPM from the O2 Sensor readings. It is rich and then suddenly goes low voltage and then back to 800+ for readings as RPM goes up.
This issue is the reason I got HP tuners. This is my first post. Ideas on what to log and how to go about solving this are welcome. Any parts that are borderline not working like O2 sensors? Even if I just capture the problem area and hire a tuner to fix it...
VCM Version 2.1.18.0
The pre tune history of this is here:
http://www.trailblazerss.com/forums/...showtopic=9498