1999 Chevy Suburban RPM Varys

JESSEJAMES405

MEMBER
1999 CHEVROLET SUBURBAN
V8
2WD
AUTOMATIC
170,000 MILES

Ok my 1999 Chevy surburban has been running weird latly it has 170000 miles on it and pretty sure its stock engine, it runs good but say when I go about 45 55 65 or even 75MPH down the high way it doesnt seem to shift gears but usally the rpms will stay at one point just depending how fast I go but sometimes the rpms will jump from 1500 ro 2000 just like that without me moving gas peddle, and it will flucuate every now and then now the SES light is on and it seems to have a Bad O2 Sensor Before the Cat on Bank 2 it says it tested Slow so I was wondering if that coould be the problem or if it is something else?

3 Replies

JACOBANDNICKOLAS

MECHANIC
109,703 POSTS

Hi:
I don't think the O2 sensor is causing the problem. When the RPM's raise for you, does the engine rev? Does the car speed up or does it seem as if the trans is slipping?

Joe

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Monday, February 2nd, 2009 AT 9:13 AM

JESSEJAMES405

MEMBER
10 POSTS

The engine does rev up yes, but I dont believe that the transmission is slipping it could do it in either 3rd gear or over drive the engine revs up but does not speed up or anything, thanks so much :)

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Saturday, February 28th, 2009 AT 10:05 PM

JACOBANDNICKOLAS

MECHANIC
109,703 POSTS

Hi:
the O2 sensor could have a role in this, but I don't think it's doing it by itself. If it is reading lean, it may tell the computer to richen the fuel, which could cause a variation in RPM's, but there is something else (I believe) causing it to rev for you. You may want to have the Mass Air Flow (MAF) sensor tested as well and the Throttle position sensor (TPS) and Idle Air Control (IAC) tested. I would think that the computer would have stored a code for them, but maybe they didn't. Finally, it does seem as though the O2 sensor is bad. You should replace it. You can do it yourself (not too hard) just to see if that changes the problem.

Let me know what you find.

Joe

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Sunday, March 1st, 2009 AT 2:14 PM