1997 Mustang rough idle?

EuroStang · 04-03-2009

lately i have been noticing that my car idles slightly at a lower rpm than usual and that the idle is much much rougher and at times feels like it will stall out (but does not). I thought it might be the spark plugs since i have not replaced them since i bought the car abt 6 month ago. my car is pretty much stock other thn a throttle body, throttle spacer and a BBK CAI so i was wondering if my car was running too lean/rich or if it was a more serious problem?

xkorellx · 04-03-2009

Make sure you check your vacuum lines.. while the engine is running listen closely for a whooshing sound of air or something. My explorer did the same thing a line just came loose.

StalkerStang · 04-03-2009

Usually a loose vacuum line will elevate the idle, and then make it run rough.

Take at a look at the IAC valve, make sure its not backed up with excessive carbon. Clean it out with carb or brake clean.

Another thing that used to be an issue with BBK throttle bodies was that the hole in the plate was either not there or not large enough I can't recall. Check to make sure that there is at least a hole in the throttle palte, there should be a small one in it.

Markstang690 · 04-03-2009

out of curiosity whats the normal idle rpm?

StalkerStang · 04-03-2009

I think its 650

EuroStang · 04-07-2009

i checked everything and didn't hear a whooshing sound, and i do have a bbk throttle body but i've had that for a while and this problem is recent, also sometimes it takes her a while to turn over...

StalkerStang · 04-08-2009

Go have autozone or similar test the battery.

If the battery is on its way out, then the car will not run as well.

jasenabw · 04-09-2009

i would check the fuel pump, my car was doing the exact same thing, the idle would go down to around 500 rpm, and it would get bumpier than following the train tracks. turns out, the fuel pump was going. everything on my car that has gone, seems to go slowly, rather than all at once. ill bet there's no check engine light also.

EuroStang · 04-17-2009

Quote:

Originally Posted by jasenabw

i would check the fuel pump, my car was doing the exact same thing, the idle would go down to around 500 rpm, and it would get bumpier than following the train tracks. turns out, the fuel pump was going. everything on my car that has gone, seems to go slowly, rather than all at once. ill bet there's no check engine light also.

yea i think its the fuel pump cuz it does idle at a normal rpm and then drops and sounds like its gonna cut out and then the rpm returns to normal, and there is no check engine light...yet

P.s. i know its not the battery b.c i just put a brand new one, less thn a month ago