Lately I've been having an issue with hanging RPMs. When I come to a complete stop the car will be idling around 1200-1400 for a few seconds then drop back down to the normal idle about 650-700. Also today on the freeway when I was cruising in 5th, I would let off the gas, but the RPM's would not drop. Has anybody had this problem with their Mach? I don't think it could be the IAC seeing as the car only has 16k miles. Maybe the previous owner installed a bad tune? The car has 4.10's so I'm guessing it could have been flash tuned to correct the speedo. Any help would be appreciated, thanks.

 

Ive had that happen to me a time or two but its very few and far inbetween, mostly when i have just started the car and didnt let the engine choke all the way and get the idle back down to where it is supposed to be anyways... How long will the RPM's hold

 

I was going to ask the same question.. how long do they hold? Mine is slow to rev down, but they don't really hang or anything.

 

I would say when I've just come to a stop the RPMs hold for about 3-4 seconds. Also, when I was shifting through the gears just driving normally it seemed like the RPM's were not increasing smoothly. They would jump or skip, thats the only way I can describe it. The engine runs really smooth but the tach was being weird when accelerating inbetween shifts. Keep in mind this is just normal driving, shifting around 2000 rpm.

 

I think they all do that and if anybody knows of a fix for this I would love one I bought an SCT tuner and thought maybe it would take of this...but it didnt.

 

Yeah mine does the same thing only at about 1000-1100 rpms. My tach also gets stuck from time to time... Bugs the hell outta me!

 

I guess I shouldn't stress about it too much then, sounds normal. Either way I'm having the car dyno tuned at Blood Enterprises in Auburn, WA in a couple of weeks (Fstangg may have heard of this shop). The car has minimal mods, but I'm curious to see what kind of numbers it will put down on the mustang dyno. Being the 2nd owner I dont know everything that has been done to the car, but I want it running in prime condition.

 

There is an easy modification to do for this. What causes it is the idle air control valve. If you make a gasket for the IAC that has a smaller hole in it, it will cause the rpm's to drop more quickly.

check out http://www.mach1registry.org/forums/...hlight=IAC+rpm

 

hey blackened let me know how the dyno session was at blood enterprises, i also heard that john at horse power ranch is pretty good too.

 

Same here!!!! first time it happened i thought i was going to crap myself because it took like 15 minutes for the freakin thing to start working again... for some reason ive had quite a few electrical issues with this car, nothing major, just little annoyances