Revving up when starting.

[codemonkey]

My car has done this pretty much since day one. I start the car, it quickly revs up to about 2k then drops back down. No big deal, but this is upon immediate startup, when the oil is sitting in the bottom of the pan.

I figured it might be a throttle position sensor, but I replaced it when I put the new throttle body on. Oh, I also replaced the throttle body, and it still does it.

The strange thing is, it doesnt do it all the time. It does it warm or cold, and so intermittently that I cant nail down what it could be. If I'm driving it hard, or babying it before shutting it off, doesnt matter. Temperature outside doesnt matter. Engine temp doesnt matter. Amount of fuel in tank doesnt matter.

Anyway, it did it all day yesterday, and at least 9/10 times it does it lately. Anyone else have this problem?

 

[Rootus]

I can't remember about the older Mustangs, but for the last 10 years or so it's been normal to see a burst of RPM on startup. The EEC does it on purpose.

 

[1993c0bra]

yeah my 91 gt had the cobra EEC when i got it, it had the19lb injectors and stock MAF, it did that until i upgraded to the stock cobra injectors and MAF

 

[1993c0bra]

i also installed the cobra manifold and aluminum heads too

 

[codemonkey]

Yeah, pretty much everything with my fuel system is stock, injectors included. Maybe I'll just have to live with it.

 

[Scooby5.0Doo]

my 89 didnt do it but my 88 does it and its about 1600 form me

 

[ddonaca351]

Yeah, pretty much everything with my fuel system is stock, injectors included. Maybe I'll just have to live with it.

If you have a chip burned for it, tell the tuner and he can get rid of this no problem.

Dave-

 

[codemonkey]

If you have a chip burned for it, tell the tuner and he can get rid of this no problem

I dont have a chip burned for it yet. I figure I'm going to wait till I put heads, a cam and injectors in it before getting a chip burnt. Then its off to the races!

 

[rogue109]

My car might not qualify for this, but my '04 Cobra does the same thing...it's all pretty much stock and it's done it since the day I drove it off the lot.