[ViperPilot24]

Intermitant problem when I put car in neutral the idles will hanga bit before dropping, or sometimes increase when shifting thru the gears. Anyone know why this would happen or what the potential fix is?

[Barricade81]

Originally Posted by ViperPilot24 Intermitant problem when I put car in neutral the idles will hanga bit before dropping, or sometimes increase when shifting thru the gears. Anyone know why this would happen or what the potential fix is?

Had something similar with my '01 3 years ago, except mine would actually never drop to the normal idling rpm (600 give or take), but it instead always wanted to idle at 1000-1100 no wonder what I tried. I also experienced the rpms going up slightly when I would upshift. Also when I would exit off interstates, it would stay around 2k for a good 10 seconds before falling to the 1000 mark where it would idle again.

Finally took it in to get it checked and it turned out I had a bad Throttle air bypass valve assembly. It was causing my car to run rich and ended up screwing up my injector system too. My car smelled like gas as I pulled into the garage. Had I gone much longer it might have been ruined. It was a hefty repair.

I'm not saying this is what you have, and I hope it's not. If you check it out early enough, you might not have anything major on the side to deal with also. Hopefully your case is something far simpler.

[Barricade81]

Originally Posted by ViperPilot24 Intermitant problem when I put car in neutral the idles will hanga bit before dropping, or sometimes increase when shifting thru the gears. Anyone know why this would happen or what the potential fix is?

Actually, the first thing I would do on yours is disconnect the battery for a few hours and let the computer reset itself. If you have a simple fix, that should take care of your idling issues. If it doesn't, then there's something else.

[Barricade81]

Originally Posted by ViperPilot24 Intermitant problem when I put car in neutral the idles will hanga bit before dropping, or sometimes increase when shifting thru the gears. Anyone know why this would happen or what the potential fix is?

Actually, the first thing I would do on yours is disconnect the battery for a few hours and let the computer reset itself. If you have a simple fix, that should take care of your idling issues. If it doesn't, then there's something else.

[Barricade81]

Originally Posted by ViperPilot24 Intermitant problem when I put car in neutral the idles will hanga bit before dropping, or sometimes increase when shifting thru the gears. Anyone know why this would happen or what the potential fix is?

Actually, the first thing I would do on yours is disconnect the battery for a few hours and let the computer reset itself. If you have a simple fix, that should take care of your idling issues. If it doesn't, then there's something else.

[nysiv16]

my car also does that...did you put in a new CAI by any chance...when my car was idling bad the mechanic changed out the MAF and the IAC motor...also said i needed a tune up...try cleaning out your MAF...hopefully that might do the trick

[Rich J]

You don't need to disconnect the battery for a couple hours to reset the computer. 15 minutes does the trick.

I had that problem, I would put it in park or neutral and my idle would hang at 1-1.2k rpm's. And would only drop if I put it in gear. I replaced my DPFE sensor and it fixed it. Clean your MAF with MAF cleaner, DONT USE ANYTHING OTHER THAN THAT TO CLEAN IT AND BE VERY CAREFUL. And clean your IAC with Throttle Body cleaner. Should fix your issue. If not let me know.

[ViperPilot24]

replaced my DPFE sensor and it fixed it. Clean your MAF with MAF cleaner, DONT USE ANYTHING OTHER THAN THAT TO CLEAN IT AND BE VERY CAREFUL. And clean your IAC with Throttle Body cleaner.

Do What???? ok like how do I clean my MAF? please break this down barney style for me. IAC? A little help for a newby.

[ViperPilot24]

ok so tracking with the MAF. just reading thru the haynes manual now on how to pull it so i can clean it...but DPFE sensor?

[ViperPilot24]

ok...found good write ups on this on muscular mustangs . xxx

[Matt.]

tell us how it goes

[ViperPilot24]

I cleaned the MAF but still seems to be functionng the same.

For example, I will be going up hill and when I hit the top of the hill say around 2nd gear at around 2.3k and start downhill alot of times i will just pop into neutral and coast down hill and the idle will drop to 950ish-1.2K. Only when I come to a complete stop will it settle down to around 700ish. there have been a very few time that when i do that the idle will drop immediately to 700ish but that is the exception.


And most of the time something similiar happens when exiting the freeway off ramp from 5th gear around 2 - 2.3 rpm at 70mph i will pop into neutral and coast to the light at the end of the exit ramp it will do the same as described above. is this right?

I did read another thread where it talked about this is normal due to some sort of pressureized brake system (?).

I havent pulled the IAC yet cause the picture in the manual i have is kinda deceptive and I was looking for a good photo showing specifically where it is located. The write up i saw explaing that it is just pulling to bolts and removing it and spraying it down with the throttle cleaner and then reinstalling.

Any comments or suggestions from anyone would be greatly appreciated.

[ViperPilot24]

ok..found the IAC...actually mounted on the 'back' side of the Throttle body (looking from the front of the engine compartment) will clean that tonight and see what happens.

[Codeman]

It is a very common problem on this car. And definately try cleaning the IAC otherwise some have went to an IAC restrictor plate to restrict the airflow at idle to prevent it.

[ViperPilot24]

cleaned the IAC tonight. took for a test ride and throttle response improvement was def noticiable. seemed like the 'return to idle' in neutral was much improved. gona give it a week and do a second cleaning just to see how things go.

Codeman. While I appreciate the restrictor plate idea you and others i have read mention, I dont like the idea of trying to self modify something like that. One, it seems like a hack job, and two, if they wanted it with smaller holes, they would have made it that way, but defently....thanks for the suggestion.