2003 SLE with 206,000miles. When driving down the road about 60mph (16-1700rpm) I feel a jerking sensation in the car like it is missing. All other times the thing runs great. If I pull it into 3rd gear which is about 2100 rpm it does the same thing. Accelerate and it is just fine. The car is fairly well maintained with plugs and wires in the last 10,000 miles. I also cleaned coil bases and ICM connections at the same time. Any thoughts? I recently drove about 45 miles. The first 20 miles acting up around that 1600 rpm range at 60MPH. All of a sudden it stopped doing the rest of the way. Has been doing this for about 3 months.

How many miles since the last transmission service?

How many miles on this transmission?

Original transmission and about 10,000 miles since oil change. Shift kit installed about 30,000 miles ago. I have learned that I can get it to do this at other speeds. I think it is related to a certain throttle position. Not open very far. Sometimes it is bad and sometimes it does not do it.

Any codes or engine light? Have you cleaned the throttle body?
TPS Sensor may be going bad?
https://gmforum.online/forum/general...sors-locations
IAC and port cleaning..: https://www.gmforum.com/normal-maint...2/#post1597076

Have had the evap code for a long time but no others. I can check again. I cleaned the throttle body around 100,000 miles so maybe need it again. I changed the TPS 3 weeks ago thinking it might be that but no change. Thanks for the input.

I have a concern about a shift kit being installed on an old transmission.

Does the RPM go up with these events or down?

Are you using DEX 6 trans fluid?
What was the EVAP code #?