I have a 98 v-6 automatic camaro that runs great except for one thing. After it gets warmed up (about 30-45 mins of straight driving) if I'm steady about 60mph on the highway, the car will rev and the tach will jump about 750 rpm and then back to normal. About 2,000 rpm. I have had it at multiple shops, and even let the repair guy ride with me with the computer hooked up and he saw nothing that the computer was doing. I am soooo frustrated with this problem. When it begins to do this it will continue to "jump" about every couple minutes until I speed up above 75mph, then it stops. If anyone knows what might be going on, I would really appreciate some insight. By the way - my only mods are a dual Flowmaster exhaust and a SLP Whisper lid w/K&N filter. Any help would be greatly appreciated.

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"just doin what I can"

 

may be a bad crank sensor. it won't throw any codes.

 

I vote for the throttle position sensor. Get the voltage checked through the full range of motion.