I am looking for more help on the bouncing RPMs. I know I've already brought this up, but having successfully replaced the intake manifold gasket I have mostly eliminated the larger problems I had before. It's now only happening in 3rd gear at 20mph, and only when the engine is cold. If I apply the brakes and slow down, or speed up and then coast at a higher speed, it doesn't happen. Nothing at all when warmed up. If I put it in neutral while it's happening, it stops bouncing. Which leads me to ask, would a transmission problem throw the CEL? The CEL has not come on in a couple hundred miles. The tranny is filled with genuine Honda ATF, and it's properly filled (level is in the hatched area). I don't think the torque converter is locking and unlocking because both the tach and the engine fluctuate, and it's not a light jerk as if the converter clutch was engaging. It's more like a light pulsing, but it is noticeable. I'm doubting it's the tranny, but then again, what do I know. What could be some other causes/items to check/test? The nuts around the intake are snug, the gasket is properly positioned, and everything is in its place. These problems only came up after I finished the head gasket replacement several months back. I made especially sure that all gasket surfaces were SPOTLESS and STRAIGHT, that the valve lash was properly adjusted, and that the head bolts were all properly and sequentially torqued to specs. I also cleaned the throttle body and intake manifold. Could a sensor or two have possibly been damaged from cleaning the intake/TB with oven cleaner (no surfaces were etched)? Sorry for the long-winded explanation, but I hope everything makes sense and I just don't want to tear random stuff apart that is totally unrelated. Thanks again in advance; you guys have been a great help!

 

If the PCM "sees" something wrong with the trans it will set a code and many of them will set the CEL light as well. So I would check for any stored codes in the PCM just to be sure.

After that I'm kind of at a loss as to what the issue might be. There is a "idle re-learn" procedure you could go through just to rule that out, but you have been driving the car for a while so it might not help......but it only costs a little bit of your time.