Help ! Runaway Engine ..................

Hi I'm new to the forum and need your help.  I recently purchased a 1999 Wrangler Sahara, with 4.0L and auto transmission.  It has about 82K on it.  I installed a Banks cold air intake and Banks cat back exhaust.  We took it on it's first long trip this weekend and on four occassions, when we slowed down to stop for a light the engine took off by itself and raced wildly.  The first time I almost couldn't hold it with the brakes and nearly hit the guy in front of me.  The next three times I slammed it into neutral and it came back down to normal idle.  Now when I slow down and stop, if I feel the engine starting to race, I put it in neutral and it goes back down to normal idle. Any ideas what could be wrong? Thyaks a lot in advance.  I really love the Jeep but am hesitatnt to take it anywhere.  

Did you install a throttle body spacer with your cold air intake?  

Does it have cruise?  I'd try pulling the plug or fuse for that and see what happens.  I'd also check for vacuum leaks.  
99tj/ 4.6 stroker / 4.88 / '06 rubicon axles / 7"rockkrawler l/a / steering upgrade / agr pump psc box and hydro assist / mm 10.5k hyd. winch / 35" Trxus MT / comp cams xtreme 4X4 cam

also check to see if you crimped the throttle cable.  
I work to support my Jeep

Thanks for getting back to me.  No I did not install a spacer.  Banks instructions never mentioned one.  

Thanks for the reply. Nope, no cruise.  I will check for leaks though.  

Thanks for the tip.  I'll check for crimps too.  

That's good that you didn't install a throttle body spacer. They do absolutely nothing. Often times, they cause problems with throttle linkage, hood clearance, and if not installed correctly, vacuum leaks. Vacuum leaks are the most common cause for an engine to race or have goofy idling problems.

If you use a propane torch, valve on but not lit of course, and wave it all around the intake manifold area, you can detect vacuum leaks. The engine will idle up a little if it sucks in a little propane.  

Wow, thanks for the info. I was just about install a spacer. Back to Quadrtec   It did it again today and we almost lost it at an intersection.  I'll try the propane tonight.  Problem is it's very intermittent.  It hasn't happened for about three weeks.  Seems to do it when it's either hot out or if it's been sitting in a parking lot.  I might just change out all the vacuum hoses to be safe,  Thanks again.  

If it's random, another thing that I might suspect is the Idle Air Control (IAC) valve. They get dirty, gummed up, and stick. You might try removing it and cleaning it. The auto parts store has a special cleaner just for the IAC.