High Rev/Low Acceleration
Hi Guys, I could use some help. I'm experiencing two issues that might be related.
First, I will try to accelerate from a stop only to have the RPMs rev up as if I'm in neutral but will only creep along with a touch of actual acceleration. I can tell that the transmission is doing some work but not what should be done by the level of RPMs I'm at. This happens very infrequently, which leads me to think it might not be the transmission entirely. It also seems to happen when it's very cold out. It doesn't tend to happen on initial start-up, but after a minute or so. For instance, after work I'll drive to the guard shack and check out, then up the hill to the light, where it will happen when the light turns green. Last time, it gave me absolutely no acceleration until it hit 4K rpms and wouldn't go in reverse either. I had driven 200 yards to McDonald's and gone through the window only to not be able to leave the driveway (also, 3 degrees F outside all night). It hasn't done it in the 3 days since. Intermittent, but got worse lately.
Second, shortly after start up, I will experience a sudden surge of rpm while stopped/stopping that makes my car surge forward until I further press the brakes. This happens slightly more regularly. For instance, it will happen when I stop at the guard shack after work.
I've recently replaced the trans fluid and saw nothing noteworthy. Oil is always replaced on time. 135K. 2007 cobalt. At 97K, the entire head was replaced for sticking valves. These symptoms seem completely different that the head issues. Once i get up and going, these issues completely die off.
My thoughts are the things like throttle position sensor or maybe torque convertor control. Maybe the transmission control module? Any help is appreciated!!