just bought the car 2 weeks ago its a 91 rs 3.1,when i bought it it was stallin i took it to the mechannic and they said they reseted the idle cause it wqas idling too low ok no more stalling.....now when im at a red light sometime the rpms drop then surge back up almost like im revving the car so far i have changed the air filter and fuel filter any other thoughs of whats causing this?

 

IAC valve or Throttle Position Sensor maybe..I'd clean or replace the IAC valve first and reset the comp and see if it keeps happening. Man, that sounds strangely identical to what my Stang is doing..but it's an idle surge from the cam. Don't have a cam do ya??

 

vacuum leak

 

Oh man how could I have forgotten that? Oh yeah, rum.

 

Check for codes. My car is doing that, but surging up, then back down.

edit: as I found out on my car, check the coil to see if it's good

 

how do i check for the codes

 

I think all V6's do that i see this post all the time and my car randomly decided it wants to surge and i have tried for years to figure out why. ITs aways when you are brakeing or have your foot on the brake doing 10mph or at a complete stop and it wil act up right??? Try reseting the computer after i did that my car didnt do it as much. Just disconnect the battary and wait 5 mins and connect it back it should help. Drive your car afterwards for around 30 mins and dont floor the car the computer needs to relearn its values.

I think it has something to do with the powerbooster when you brake takeing the vacume thats just what my conclusin finaly came to.

 

If you dont wanna reset your radio, you can also just pull the ECM fuse. Now, if I remember correctly, it's on the passenger side fender well somewhere...a black clip...if you slide the top off of it, it's got a fuse inside it..just yank that fuse for like 30 secs or 1 minute or so and reconnect it. Resets the computer but doesnt kill power to everything else.

 

i reset it so far no surging but i also changed the spark plugs too

 

Yah, that's the reason I came up for mine as well. Only really notice it when I park the thing in the garage after being out for a daily cruise. I suppose my new IAC (well, a year and a half new) could use a cleaning. Hm, time to add that to my things to do list.

-Dan