So temps have been fairly cold here in Washington recently which has brought to my attention a problem I have been having for awhile. I generally let my Jeep warm up before I drive it, but when I come to a stop, as I'm slowing down the idle dips down causing it to feel like it is going to die. It hasn't died yet, but it has come pretty close. After the Jeep has been driven and is fully warmed up, I do not seem to have the issue. For some reason, it seems to be worse when it is colder outside. I think the issue is present whenever it is cold and the brake pedal is pressed. I posted awhile back about another problem I was having when I was completely stopped where my idle would surge and the tach would bounce which may be directly related. Could it be that my booster, or the check valve on my booster is on its way out? To me, it seems as though it is some sort of vacuum issue. I've got this thing running pretty darn good compared to when I bought it...I just wish I could get this last little quirk resolved. Any input would be greatly appreciated. Thank you.

 

Take a gander around here for how to clean the throttle body. Most likely cause is that the IAC is gummed up and having trouble opening. The Idle Air Controller lets your engine breathe when you have your foot off of the throttle. After your engine warms up so does the gunk!

If still problems we can look at them then, but gooey IAC is prime suspect.

 

After you clean the throttle body and you still have the problem, look in the direction of your MAP sensor. Sometimes the barometer drop can give a hint it is going out.

 

Sorry forgot to mention in my first post, I have thoroughly cleaned the throttle body as well as replaced the TPS. As far as the MAP goes, I never really have any thought to that. Any other symptoms a failing MAP might present?

 

Wanting to stall when you press the brake or dieing.
Stumbling at HWY speed.
Quick or sudden throttle release will die or stumble.
Beware that these symptoms are similar to a mis-adjusted TPS.

 

Thanks for the tip, however this is a 1999 XJ. The TPS is not adjustable.

 

He's just giving an example we know it's a 99.
I second a sticking iac though