1999 galant low idle runs a little rough

[belair327]

heys guys my galant runs at a low idle and runs rough i changed the plugs and cleaned the iac and checked its piston to make sure it open and closes when u turn on things ac and stuff idle drops more you think the iac is weak or what else could it be thanks for any help

[BGR]

Have you modified your intake?

I used to have a CAI and my idle would run like shit. As a matter of fact, I couldn't even use my AC while at a stop because the car would die. I have since put the stock airbox back on and the idle is smooth as the day I bought it. No problems with the AC now. Quite honestly, I don't see any decrease in performance either, and I don't miss the loud growl that I would get when I stepped on the gas (I'm over that now). However, I'm also using a mixture of E85 ethanol and 87 octane for fuel and even though I don't get the gas mileage I did before, the car runs far better than it did using Premium. The punch off the line feels just the same as when I had the CAI if not better.

I had to remove the CAI as the CARB sticker was for an Eclipse GT and wouldn't pass smog. But since having going back to the stock airbox, I don't really miss the CAI.

[03-Galant-ES]

belair also check your vacuum lines for cracks or leaks or anything.

[Isaurio]

check your screw by the throttle body. adjust the screw until it feels right

[djakay]

I had the same thing on my 03, it idled low, and with ac on rpm would drop noticable. Turned out it was my IAC motor. Changed it and it idles perfect.

[johnygezony]

Have you modified your intake?

I'm also using a mixture of E85 ethanol and 87 octane for fuel and even though I don't get the gas mileage I did before, the car runs far better than it did using Premium. The punch off the line feels just the same as when I had the CAI if not better.


would you recommend that to others ?

[03chi-town0z]

some mitsus have been known for throttle plate issues causing poor idle conditions. the whole "throttle body cleaning" gimmick that has become so popular was actually very beneficial on some of the models to prevent or cure this condition, lol. this doesn't involve just spraying the cleaner into the tb though, you need to reach in there, or remove it completely, and wipe down the plate and inner channel to clean it all up. while you're cleaning it, you're going to want to disconnect the battery too so it can relearn the base throttle plate position, otherwise it will think somethng is wrong when the throttle is closing more than it used to.

hard to tell without seeing the car in person, but it's worth looking into...