94 Chevy erratic rpms

[dhud64]

Thinking of buying a 94 Chevy Pickup, SS-350. On the test drive everything was perfect except at about 70 miles per hour with the cruise on, when the truck needed to down shift it would kick itself out of cruise. (This was at about 2000 rpm...) Then, at about 72 mph the rpms jumped up and down between about 3000 and 4500 rpm. Up and down, up and down, it's just the rpm's though, it's not like the truck starts a bucking bronco act or anything...any ideas what could cause these problems? Are they related?

 

[petryshyn]

Re: 94 Chevy erratic rpms

might be a bad TPS sensor causing the erratic shifting. Try it at 75 MPH and see if it still occurs. If not, its likely at 72MPH you are running it at a bad spot on the TPS sensor travel

 

[ndemge]

Re: 94 Chevy erratic rpms

TPS sensor gave my wife a lot of trouble on her car,.. but one thing is, this is not just a gear thing, it's a Spot on the trottle position, on her car, it was right at 35mph in 4th geer, right at the speed limit for local roads, would surge up and down... check for this by noticing where your throttle is at, and downshift and slow down to try to get the same affect at a differnt spot.<br /><br />I replaced it with one from my parts car and it cured the problem.... but the repalcement had a bad spot at a differnt place, doesn't happen very often, so we just live with that one, for a $200 part on her car..... will never own a mitsubishi again

 

[dhud64]

Re: 94 Chevy erratic rpms

Thanks folks. I've decided against the pickup. The search continues...