rpm's fluctuate

2000 CHEVROLET IMPALA
100,195 MILES • 3.8L • 6 CYL • 2WD • AUTOMATIC
Avatar
THEBECK60
  • MEMBER
  • 1 POST
shifts good, no codes but between 40 and 50. the rpm's fluctuate a couple hundred rpm's up and down. Changed MAF, IAC, TPS, speed sensor, no prevail. it only does it between those speeds. highway speeds are good. have been doing a lot of soul searching and came up with a lot of different remedies. driving this backyard mechanic bonkers.
Dec 20, 2019 at 11:00 PM
Advertisement
Avatar
JACOBANDNICKOLAS
  • ✓Experienced Mechanic
  • 110,248 POSTS
Hi,

Since it is happening only at that speed, it leads me to think it is related to something other than the engine. The engine doesn't know the car's speed. If it was a specific RPM where you notice it, it would do it at any speed but specific to a set RPM.

Pay attention to see if when you feel it correlates with a specific gear the transmission has shifted into. Also, if you have a live data scanner, I need you to check the short term fuel trims when you feel it happening (throttle steady).

Let me know.

Joe
Dec 22, 2019 at 11:37 AM
Add a reply
Join 2CarPros for free, one of the most advanced car repair communities on the internet. From first-time drivers to seasoned mechanics, everyone is welcome to reply, share details, and get better answers. You can add a temporary image or video first; uploads are limited to 20 MB.

Ask a new question

Frequently Asked Problems for This Vehicle