Today while I was driving at about 45 mph holding constant pressure on the gas pedal, the rpm's on my 1990 4Runner began to jump back and forth from about 1,500 to about 2,200. My first thought is that my automatic transmission is on the way out the door after about 185,000 miles. This has never happened before, and my transmission had been performing very well given its mileage. I checked the fluid and it is fine. I was wondering if anyone has any other ideas about what might be causing this, or can confirm that it is a transmission issue.

 

Well I just took it for a 5 mile test-drive at varying speeds and couldn't reproduce the problem (go figure). I guess I will just dump some Lucas tranny fix in there for good measure and hope it was an isolated incident.

 

Was the engine actually surging or was the tachometer just twitching? My tach twitches when its cold....

 

Although my tach sometimes twitches also, I could hear and feel that the engine was definitely surging.