FAST IDLE 2003 Chevy Venture 3400SFI, this was the Battery/Low Fuel/Security

Hello all. I hope what I say in this video is correct and also does not insult anyone's intelligence.  I decided to make a video because its easier to describe what I am experiencing.  Originally, I had a topic on here for quite some time Battery/ Low Fuel/ Security.  Ultimeately I finally swapped the computer after I learned I could get one for $26.  The first one was from a 2001 Pontiac Montana.  I would always get a code that the PCM was looking for a Secondary Air Pump that does not exist on my van. I went to a newer 2005 Pontiac Montana Computer which is a better match because my van has a transmission from a 2005 Montana and the van is running fine but the idle is too fast until it warms up, and I get a random code once in a while that I do not think is related because the code usually never happens while I have a fast idle.  The codes will either be P0300 or P0131 or a PO172.   If you have time to watch video, you can drag the slider over toward the end where I show that the idle came up very fast while I was doing video but also after I had  started it and the idle was fast so then once I shut it off and restarted it, the idle was fine....but during this video the idle eventually crept up really fast.  I never experienced it like this until today doing the video.

Thanks for your time in advance.

i have 24 views on this but no responses. I know I am probably going off the reservation as to what you teach and what is in the book that i bought but I really do not have a lot of time to wrap my head around this now with all else I have going on. The van runs and I basically am the only person to drive it when I want to haul things. I would like to take it on some longer trips but I want to feel more comfortable about it. I think the problem is a 5v wire I cannot possibly get to. If I lived close enough, I would bring it to your shop. Sometimes I imagine driving down to your shop with it just to say hello and maybe you could take a few minutes to have a look at it and tell me if it is worth even putting the money into trying to fix it.

With the idle like that I would start looking at the idle air control valve. IE take it out and clean it along with the throttle body. This is typically what I find wrong with the car. (Carbon buildup or IAC stuck in a position or partially working enough not to trip a code) usually the IAC is replaced after testing the idle bi-directionally.

the other thing to look at is fuel pressure. Hook a fuel pressure gauge up to fuel rail test port and turn key to on position and observe fuel pressure. Should go to ~38 psi or 50 psi and not drop if it drops quickly you have a stuck open fuel injector or
(very unlikely given symptoms)
fuel pressure regulator is bad. (This could be two possible ways )
1. fuel bleeds back to tank causing a low fuel pressure issue off idle and lean codes for O2 sensors.
2. Fuel leaks into vac line attached to fuel pressure regulator. (You will see wetness in vac line connection point) which if leaking bad enough would possibly cause a high idle but not as high as in the video. Hense why my first thought is the iac.

If your scanner lets you look at freeze frame data look at the data and let us know what it says. It is possible you have two issues which would cause those codes.

Thanks for replying @Hardtopdr2. I cannot find anyone local to test my fuel pressure unless I want to go to a dealer. I conducted my own "laymans test" and if I press the button on the end of the fuel rail the fuel squirts about a foot while the key is in run but engine is not running. I replaced the fuel pressure regulator back in the spring because it appeared to me that the original one was slightly leaking and could smell fuel on it.

I replaced the Idler air control at least 4 years ago and I also replaced the throttle possition sensor this past spring. In late spring when I finally got this van running with a replacement computer I decided to clean the IAC and throttle body as best I could. It is pretty dirty and I might as well focus my efforts there because back when I did replace the IAC I discovered that the vacuum pipe that runs from top of air supply hose to back of motor was disconnected from the back of the motor. That could have been sucking air for years. I never took the throttle body off and cleaned it properly, all I have done was used a rag at what I could get to when taking off IAC and TPS and I sprayed throttle body cleaner while it was running. Maybe I will try that again. I am going to eventually make another video because I changed my MAF Sensor back to the aftermarket brand I bought last spring and the van runs better with it but I still get the fast idle during cold starts and if I stomp on the gas up a mountain and let of and stomp again, I eventually get the P0300.

Can you put the original PCM back in and lets just fix the wiring harness problem? GM PCM's are very robust(at least the new ones), and almost always is a wiring problem. Sorry, I didn't want to watch the video, Im running Linux and a recent upgrade has blown my codecs out and till I fix it I can't watch anything.

You can test your fuel pump with a amp meter. How much current does it require?

Have you got a link to that other thread? That pipe that fell off is the fresh air pipe, if it becomes disconnected it will allow extra air that the MAS doesn't know about into the engine, the computer will think the engine is lean, generally a p0171.