Engine high idle?

The FPR should be on the ruel rail, disconnect the vacuum line and look for gas in the line, if present then the FPR diaphram is ruptured and the FPR must be replaced.

When the car idles in neutral it idles high then low, it's not steady. What is causing this? Also, when I'm driving and the car goes into second gear it seems to lose power.

(follow-up)Thanks I'll try that this weekend. Also, the heater core on my car is gone. I took it to a mechanic he said he isolated it. Now my car overheats very quickly, I took it back to him he said he thinks the gauge is broken. I don't agree with him can the heater core have anything to do with this?

If a major tune-up has not been done recently, this could be the cause of your problem. Replace the spark plugs, plug wires, fuel and air filters, etc. Also, replace the oxygen sensor. In addition, service the fuel injection system. Clean the carbon deposits from the throttle bore and idle passages.

ok guys, time for me to throw some money back into the pot. I'm proud of my mechanical abilities but this one has me stumped. Whoever has the magic answer,

1996 Grand Am GT 3.1 V6 auto.

About 25 seconds after start up, the RPM rapidly bounce between 500 and 1000.
It does not matter if I am in any gear or park or neutral.
It doesn't matter if the engine is cold, or at operating temperature.
It does not matter if the car sat over night, or for 1 minute.

It is not a nice slow revvvvv up, revvvvv down.
it's goes bang, bang, bang, bang about as fast as you can say that comfortably. (almost as fast as a rev limiter)

After about 30 seconds of this, the idle goes to 900 and stays there. But it normally dies if I don't manually step on the pedal and bring it up to 1000.

If I start the car and immediately put it in gear and start driving, about 25 seconds into it, and doing 30 mph or so, the engine looses power for 1 or 2 seconds and then comes back.
This repeats 3 or 4 times.

when this first happened, i thought to myself, "Oh, that's got to be the IAC"
[b:82a67d6c09]Wrong...[/b:82a67d6c09]

I jumped the fuel pump relay for 5 minutes before i started the car, to make sure any possible air bubbles had circulated through the system and made their way back to the tank. And did a fuel pressure test with the schrader valve removed. (just in case the valve was causing a dampening effect)
45 with the engine off.
40~35 depending on intake vacuum.
gauge was smooth while the engine was freaking out.

I have unplugged the IAC with no change.
I have unplugged the EGR with no change.
I have unplugged the MAF with no change.
I have unplugged the MAP and it wont start.
I have unplugged the TPS with no change.
I have unplugged the evap purge solenoid with no change.

I'm ready to dance around a fire and cut a chickens head off, if voo doo is what it takes to fix it.

I would first check all system grounds. It sounds like the computer could be no good. Also I have seen were the ignition module can backfeed casuing the problem you discribe. These problems can be tough to find. I asume you checked for any vacuum leaks and checked the injectors ohms reading?

Just a thought, as you know the idle is computer controlled. GM had the wisdom to make the pcm memory volital, if you loose battery power the car forgets how to idle. This causes symptom like you describe.
It can be manually reset by starting the engine and holding the rpms at a steady 1500 for a couple of minutes. Just a possibility...

here's tonight's exciting update.

I unplugged the breather tube from the air intake and was able to keep the engine running by spraying starting fluid in the hole. Keep those ideas coming... (thank god this is my own car, I have never told a customer that I couldn't fix their car)

did you try unplugging the 02 sensors?

2001 Pontiac Grand Am/93,000 miles/V6(3.4L)/Automatic Transmission
1. My car idles too high upon start up and while driving. I often need to turn off the ignition and restart a couple of times until the RPMs go down to normal. It also revs too high in drive and my car seems to accelarate on its own without putting my foot on the gas pedal (especially at lower speeds). I often throw it in neutral to preventmy car from moving forward and wearing out my brakes when at a stop light. However, the RPMs race up in when I put the trans in neutral and burns more gas/makes car run hotter. No engine lights/servicelights come on. I keep up with all maintanance and had my car at three shop to correct this problem.
2. Also, my steering wheel vibrates excessively when depressing the brakes to slow down while traveling at higher speeds. Recently put new pads, drums and rotors on my car.

My relative experience is on my wife's 93 Grand Am. I know the year is way different, but mileage is only 120,000 so not too far from where you are. Her car vibrated (left - right) and her steering wheel shook/turned back and forth between ~50-~65 mph. The culprit was worn strut mounts combined with poor alignment.

Just had that problem with my girlfriends car after changing her thermostat. I had removed the top of the air filter holder and the mass air sensor to get to it and put everything back together. Apparently I broke the gasket that connected the mass airflow assembly to the engine. Used some gasket sealant for a temp fix and it solved the problem. Hope that solves yours!! Cheers!!!

1999 Grand Am SE, 70000 miles, V6 Engine. Over two weeks ago there was a flood near my house and the car got water in it. The water was up over the tires but not the hood. We got the car out of the water within 30 minutes. Recently I took it on a trip (about 300 total) and it ran fine but the next day I noticed it idling high (1500 rpm) and it began to accelerate on its own. I have to ride the brakes to control the speed and when I put it in park the idle surges to 2250 and gets higher the longer it stays in park. I took it to 2 mechanics and the second said it may be the computer is messed up but I have to take it to a dealer to get fixed. Are there any other possibilities and how much would it cost to replace/fix the computer?

The exact words from the guy I talked to was "the computer is messed up and its probably because of water damage" I just found the receipt from the place and it says the rean a diagnostic test and the PCM was bad and it was probably damaged from the water. I don't doubt their ability but I find it odd that it would malfunction nearly 2 weeks after being in water. Also where is the PCM located because I'm not sure the water went high enough to damage it.

I'm located in Saint Albans, WV (outside of Charleston)

This could be the PCM but I would not replace it if they are saying "it may have been damaged"

They should be able to test this and determine if it in fact is the issue or not.

I am attaching the process on how to replace it and relearn the crank sensor.

I also attached the process to replace the idle air control valve as this would be more likely the issue if there are no codes.

If there are codes, please supply those and we can determine next steps. Otherwise, I would replace the IAC as it is cheap and controls the idle speed. Let me know what questions you have.

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

Thanks