revs up when starting.

[eeh1025]

Hey there i havent started my stang in about 3 months, i went to start it yestarday, theres about 3/4 of a gallon of gas in the tank(not Much), when i started it the first 2 turnovers in shut of then i got it running good, i shut it off and then about 5 mins later i started it up and it reved to like 2800 RPM then slowly droped to about 1000, took about 25 seconds to drop, what do you think this could be, thanks alot

 

[RsStanG1987]

Maybe your throttle body is gumed up and needs to be cleaned. I had a problem like that with my camaro and i sprayed it in the throttle body around the sides and it stoped doing it. reved fine after.

 

[Mustang5L5]

Most cars have a cold idle-up feature.

When the engine is cold, the idle will race at 1500-1800RPM for a while and then drop down to idle.

Yours revved higher, so many something is gummed up keeping the TB hanging open or the IAC stuck open

 

[HISSIN50]

agreed with above. last thing - a vac line or gasket coulda taken a poo on you while it was down.

Mike, can the IAC open its dwell enough to allow that high an idle? i ask you because you are pretty conversant with how much adaptibility it has built in.

 

[Mustang5L5]

Mike, can the IAC open its dwell enough to allow that high an idle? i ask you because you are pretty conversant with how much adaptibility it has built in.

No, usually the IAC can only open up enough to maybe give you a 1800RPM idle.

But that assumed the idle is adjusted properly. Sometimes the idle is wrong and the car needs a completely open IAC just to hold 1000RPM.

There are a lot of things than can give you a 2500idle surge. Hard to speculate without seeing

 

[HISSIN50]

No, usually the IAC can only open up enough to maybe give you a 1800RPM idle.

But that assumed the idle is adjusted properly. Sometimes the idle is wrong and the car needs a completely open IAC just to hold 1000RPM.

There are a lot of things than can give you a 2500idle surge. Hard to speculate without seeing

i hear ya, Mike. thanks for the info (i was not saying it to dispute you in any way - i was just curious how much ability it had to raise the idle [for my own edification].

 

[diablostang]

My car could use that feature, when cold starting it, I gotta use some throttle to keep it running till it gets warmed up

 

[Boostin]

My car could use that feature, when cold starting it, I gotta use some throttle to keep it running till it gets warmed up

Me to, is this normal, would increasing the timing up a little where it idles higher fix this problem?

 

[crunchie12268]

yeah, I had that problem and my throttle body was gummy. You haven't started it for a while so just check to see if it happens again, if it does and keeps happening then start cleaning. Can't the EGR valve play with your idle?

 

[HISSIN50]

Can't the EGR valve play with your idle?

EGR should not work at idle. if it does (meaning it is malfunctioning), depending upon how much it is open/leaking, the idle will be very poor or the car will die.