Here is my problem - I'll be going about 60 MPH and the tach will be pretty steady around 2000 RPMs, then suddenly it will go up to around 3500-4000 RPM for no apparant reason and what I do is let up on the gas pedal and it goes back down to where it was. But it does this about every 4-5 minutes while I am driving on the highway. Any ideas what is causing this and how it can be fixed? Thanks!

 

You may have a bad electrical connection, or the alternator not holding the voltage to spec, but really need more info. What year engine & what type ignition? Is tach stock or aftermarket?

 

Sounds like your trans might be slipping.

 

It's a 98 camaro 3.8L V6 with 220k miles

It actually has about 500 RPM swings... if I am going at about 1800 RPM it will swing up to about 2300 RPM every so often and then go right back down to 1800 RPM. If I am going at about 2200 RPM it'll swing up to around 2700 RPM every so often and then go right back down to 2200 RPM. Happens about every 5 minutes or so and it has been doing this probably for about a year now (with regular driving) to be honest.

Everything is stock. No after market gauges or performance parts. I am the second owner. I've had it since it had 36k miles.

Any help is appreciated,

Thanks

 

It could be the torque converter clutch (TCC) engaging and disengaging. This is a normal thing, especially when trying to hold a steady speed on upgrades. On a level road doing about 50 MPH on OD, apply more pressure on the gas pedal, continue applying more gas until the TCC disengages, check the tach & see how many RPM the engine picks up while going at the same speed.