I have a 2000 Blazer and the RPM's keep reving when I am sitting at a red light or in traffic. It is also using alot of gas with this happening. The throttle position sensor has been replaced but did not fix the problem. The check engine light is not on. Could someone give us an idea on what the cause might be?

Thanks, Jennifer

 

Assuming The CEL lamp works.....TPS should set a code....as would IAC.....

Does the truck smell of raw gas? Does it run well at highway speeds? Does it Puff black smoke on acceleration?

A Leaking fuel pressure regulator can cause excess gas to be ingested into the cylinders, and could possibly "REV away", as you describe....

First , ensure there are no "Vacuum leaks" , as this can "Trick" the IAC motor into doing things it shouldnt be doing....There isnt much in the way of "Obvious" vacuum problems, so a quick look should pick out any thing abnormal.

Replacing the regulator involves removing the Intake manifold, and swap. Fairly straight forward, but unless your completely comfortable with this, It may be wise to get some estimates, espacially if this is "DAILY TRANSPORTATION"

 

start with running engine check for error codes at any major parts store, done free. that's a starting point.
if it does it only while sitting at the red light/traffic stops, meaning - D is engaged - it might be transmission related. try shifting into neutral or P and see what happens. if it does change, then it's one of them trannie sensors.

btw, make sure that you are not pressing both brake and gas pedal, even so slightly, at the same time. i've done it oh so many times. some cars have both pedals or so close...

 

i don't believe that any of the transmission sensors are used for engine controls.

 

carguyinva you are correct! I would look at Iac and vacum leaks. Check codes, go from there.

 

okay i'm showing my age again but on some of the older gm and fords a bad cruise control could give you the same symptoms. but that being said unclediesel gave the best answer
Murphy was an optimist

 

Thankyou for the vote of confidence......

Technically , That was an area that did deserve some thought...but didnt get it......Even though there is no cruise cable..... What about the Throttle being Mechanically "STUCK" beyond the "closed Throttle Point"??????

Kinked throttle cable, a piece of junk stuck under the blade, A missing locknut from the back of the Idle screw? These would all give the mentioned Stuck cruise servo symptoms.