What causes engine to idle at 4000 rpm - 1997 Oldsmobile Aurora

sounds like you have a vacuum leak that is causing the high rpm. it could be an intake gasket, vacuum hose or a problem with the egr system.

STOP doing that, forget about it, your going to blow your engine !

the computer is going to shut fuel to protect the engine thus limiting rpm, if there are no other problems with idle or throttle what its doing apears to be normal.

Hello and welcome to FixYa!
This can be caused by a faulty IACV (idle air control valve). If the IACV is faulty the engine can misfire or can cause stalling. The IACV is located on the throttle body. You may need to just clean it for the strainer can be full of dirt. If cleaning doesn't resolve it then you may need to have it replaced.
Hope this helps and thank you for using FixYa! Have a good one!

Go to www.hmaservice.com and register your vehicle by VIN #..
you'll then have access to wiring diagrams, shop manuals,
service bulletins, illustrations, etc. To diagnose a 2000 or 2001 1.5L Accent Diagnostic Trouble Code (DTC) P1128 (FUEL SYSTEM LEAN -- PART LOAD), check the following:

• Check the intake system for air leaks.
• Check that the Mass Air Flow (MAF) Sensor (P/N 28164-22610) operation meets the specifications listed below. If the MAF sensor output is significantly lower than the reference value (10% or more), then replace the MAF sensor.

Table 1: Using the Hi-Scan Pro in the Hyundai Diagnostic Menus Current Data Screen TPS (%) 0
3.5
5.1
7.4
MAF (kg/h) 10
21
30
47
RPM IDLE
2000
3000
4000
Table 2: Using the Hi-Scan Pro in the OBD-II Menus Current Data Screen TPS (%) 0
3.5
5.1
7.4
MAF (g/h) 2.8
6
8.5
12.7
RPM IDLE
2000
3000
4000

WITH MANUAL TRANSMISSION

Table 3: Using the Hi-Scan Pro in the Hyundai Diagnostic Menus Current Data Screen TPS (%) 0
2.4
3.9
5.9
MAF (kg/h) 9.5
19.4
28.8
43
RPM IDLE
2000
3000
4000
Table 4: Using the Hi-Scan Pro in the OBD-II Menus Current Data Screen TPS (%) 0
2.4
3.9
5.9
MAF (g/h) 2.5
5.5
8
12
RPM IDLE
2000
3000
4000

mcdevito75 here, Sounds like the idle speed motor or the idle speed sensor is no good. Your local shop can check this out for you.

It should not idle that fast anyhow. Normal idle is 750 RPM

I'm not sure but sounds like you might have a few vacum lines that are rotted and sucking air in them. I would start checking all your vacum lines to start with. good luck

vacuum leaks

hello, i first must ask why that engine would EVER be reved to 4000 RPM? it is likely you are up against the rev-limiter and your ignition is made not to over rev. be very careful....4000 RPM on that engine could/will severly damage your tourque convertor........very expensive it is common for the EGR passages on that model to plug up with carbon, remove valve, clean ports, and retest for low speed miss/hesitation, good luck....marty