94 ss

problem im having is at idle with or with out the a/c on the rpms drop from 800 to 150-200 for about 2 to 3 seconds than it idles back up to 800. this just started in the last couple of weeks then this morning it happened every time i stopped. car has plenty of voltage and runs good while driving. my question is could my fuel pump be going out, ist never been replaced and the car has 256,000 miles on the clock. any help would be helpful. thanks in advance.

94 ss

2 to 3 seconds is a little exagerated. when the rpms drop the motor wants to die so i give it a little gas it will idle up than it will run fine till i stop at the next light.

Formula350

iTrader: (3)

I'd say your IAC is bad/going bad. They're cheap, so not a bad thing to replace anyways if it has even 50K miles heh While you're doing stuff, check your TPS voltage and O2 mV

Fryrice

Def sounds like IAC. I know on my Mustang I can clean it out with carb cleaner real good and that will fix it for a while.

Id say try that just to verify thats your problem. Then replace it as suggested.

94 ss

the IAC was replaced last week and the TPS was replaced a few months ago. another thing this may and may not be related to the problem, the cars hard to start in the morning i have to turn it over three or four times. what gets me is after it starts you can turn the car off than turn it back on and it starts right up until it sit for a couple of hours.

BattleShip

The IAC could still be bad, not impossible that rebuilt part is bad. Did you clean the TB? Did you cause a vacuum leak? Vacuum leaks will cause idle to be erratic

94 ss

i did clean the throttle body and used a new gasket. the car runs better and the idle is smoother except for the occational drop in rpms.