Bad idle and deacceleration

pimpjuice01 · #1 (**permalink**) 07-06-05, 01:42 PM

I have a 93STS and the car seems like it always wants to go and now slow down, everytime I let go of the the it seems like it has a auto cruise control and it doesn't want to slow down that much and I tend to have to use the break a lot. When I do see it slow down on the tach it goes up and down slightly as it goes down, also when I'm stopped the idle is kinda bad going up and down slightly but smoothly also. I have no engine codes at all and have changed the isc motor once before, anyone have any idea what could be causing thiss?

**Ranger** · #2 (**permalink**) 07-06-05, 07:42 PM

Look for a vacuum leak around the manifold, T/B or hoses.

pimpjuice01 · #3 (**permalink**) 07-15-05, 04:02 PM

What would the normal idle be, because the car seems to always want to go even when stopped not too much but when you let go of the brake it takes off pretty easily

mcowden · #4 (**permalink**) 07-15-05, 04:09 PM

Normal idle is about 750 RPMs. You have a vacuum leak somewhere as Ranger suggested already or the ISC is bad. Listen very closely for hissing all around the TB, hoses, brake booster line, PCV valve and hose, around the intake manifold, pop-off valve, everything involved with vacuum or intake. You may also need to clean the throttle body bore and blade with an old toothbrush or some rags and carb cleaner. Clean the edges of the blade very well and make sure the whole mechanism moves freely, closes all the way, and doesn't stick at any point. When you're done with that, disconnect the battery for 30 seconds to reset the short term memory and idle calibration. Let us know what you find after this stuff. It doesn't take long.