High idle and revving?

Did you clean the throttle-body? Any applicable trouble codes? How high do the rpms go? Maybe a vacuum leak? If it happens at idle in park, block off the mouth of the throttle body, see if any effect on the idle, should be a big effect. If no effect, you have false air getting in there from somewhere. If everything checks out it sounds like the PCM is going bad.

This guide can help us fix it.

https://www.2carpros.com/articles/engine-idles-too-high

Please run down this guide and report back.

Yeah, if the problem is intermittent, it can be a pain to track down. Can you put a scanner on it that shows live engine data?

Are you losing engine coolant or engine oil? Might be an issue with lower intake gasket?

Put a scanner on it, that shows live engine data. Look at idle and idle required, they should be close to the same. You can also look to see if anything is being commanded ON, like the ac. Also, I'd have to look at sensor signals, to see if anything doesn't look right?

Hey JSC21583,

I would service the mass air flow sensor becasue this is what it does when it is dirty.

Also check the air intake boot for tears, this will fool the maf and cause stalling and low power.

Here is a guide to help you.

https://www.2carpros.com/articles/mass-air-flow-service

and

https://www.2carpros.com/articles/how-to-replace-a-mass-air-flow-sensor-maf

and

https://www.2carpros.com/articles/replace-an-air-intake-boot

Please let us know happens so it will help others.

Best, Ken

It sounds like the PCM is going out, I would try a used unit and plug it in to see if it fixes it.

Here is the location (below)

Please let us know what you find.

Cheers, Ken

Nice work, we are here to help, please use 2CarPros anytime.

Hi,

The high idle can be the result of a few things. Things such as an engine vacuum leak, faulty idle air control valve, dirty throttle plate and so on can cause it. Take a look through this link and see if it helps:

https://www.2carpros.com/articles/engine-idles-too-high

Also, here is a link to check for vacuum leaks:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Next, there is a component called an idle air control valve (IAC). The IAC is responsible for maintaining the engine idle speed. If it is dirty or not working properly, it can cause an erratic idle. Take a look through these links:

https://www.2carpros.com/articles/idle-air-control-valve-service

https://www.2carpros.com/articles/how-to-replace-an-idle-speed-control-motor-iac

If you find the IAC is the issue, here are the directions specific to your vehicle for replacement. The attached pics correlate with the directions.

____________________________

2003 Pontiac Grand AM V6-3.4L VIN E
Procedures
Vehicle Powertrain Management Fuel Delivery and Air Induction Idle Speed/Throttle Actuator - Electronic Service and Repair Procedures
PROCEDURES
IDLE AIR CONTROL (IAC) VALVE REPLACEMENT

REMOVAL PROCEDURE
1. Remove the throttle control cable bracket from the throttle body.
2. Remove the canister purge valve.

pic 1

3. Disconnect the idle air control (IAC) electrical connector.

pic 2

4. Remove the idle air control valve attaching screws.

pic 3

5. Remove the idle air control valve.

pic 4

6. Remove the idle air control valve O-ring.

INSTALLATION PROCEDURE

NOTE: The IAC valve may be damaged if installed with the cone (pintle) extended more than 28 mm (1-1/8 in). Measure the distance that the valve is extended before installing a new valve. The distance from the idle air control valve motor housing to the end of the idle air control valve pintle should be less than 28 mm (1-1/8 in). Manually compress the pintle until the extension is less than 28 mm (1-1/8 in).

pic 5

1. Install the new idle air control O-ring.

pic 6

2. Install the idle air control valve into the throttle body.

pic 7

3. Install the idle air control valve attaching screws.

NOTE: Refer to Fastener Notice in Service Precautions.

Tighten
Tighten the screws to 3 N.m (27 lb in).

pic 8

4. Connect the IAC electrical connector.
5. Install the canister purge valve.
6. Install the throttle control cable bracket.
7. The powertrain control module (PCM) will reset the idle air control valve whenever the ignition is turned ON, then OFF. Turn ON the ignition, then OFF.
8. Start the engine and allow the engine to reach operating temperature.

___________________

Let me know if this helps.

Joe

Hello,

It could be the EGR valve is stuck open. Check the EGR valve pintle position for sticking open. And it could also be the lower intake manifold gaskets leaking manifold vacuum on the bottom side this it very hard to diagnose because the gaskets are like plastic and crack and break on the underside of the intake manifold and can be leaking between intakes ports. If you can get a data list reading on a scan tool check the manifold air pressure sensor for an high reading and the O2 sensors readings are low. I'm attaching repair guide and views of the intake manifold below. let us know if this information was helpful.

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

Thank you
Joe T.

No its not normal-could be the throttle body/plate needs cleaning. Too fast an idle speed. If an engine without computerized idle speed control is idling too fast and refuses to come down to a normal idle speed despite your best efforts to back off the carburetor idle speed screw or air bypass adjustment screw (fuel injection), air is getting past the throttle somewhere. Common leak paths include the carburetor and throttle body gaskets, carburetor insulator spacers, intake manifold gaskets, and of course, any of the engine's vacuum fittings, hoses and accessories. It is even possible that leaky O-rings around the fuel injectors are allowing air to leak past the seals. Another overlooked item can be a worn throttle shaft and a defective idle speed speed control motor/valve stuck in the extended (high idle speed) position/throttle position sensor.