Irratic Idle?

[turbo90gp]

Whenever I cold start my car, it revs up high, then keeps bringing up the rpm's until I put the car in gear and then drive it around for a minute or two.  Then, the idle is still higher then what it used to be.  I dunno what the huk is going on.

[eclipse5302]

Hmm...

First, try to not put it in gear at anything above 1500.  Let it sit for a minute, or until the RPMS drop.  Putting it in to gear at high rpms is very bad for the transmission.

Now, when it did start doing this?  Out of the blue?  Has anything changed (weather/new parts)?  How does it run otherwise...especailly once it warms up?

Do a visual of the engine...look for loose wires, plugs, vac lines, or anything that doesn't look right.

You may have a vaccuum leak.  Easiest way to check this is to get a can of brake cleaner (the really flammable kind--the stuff that dries very fast), and spray it around the upper intake manifold gaskets, vac lines, etc.  Do it only when the engine is cold, and don't spray too much!!  A fire will start.  Spray a little, let it dry, then do it again.  If there is a vac leak, the brake clean will get sucked in to the engine through it and cause the rpms to change...either go up or down.  There is your problem.

It could also be injectors, but thats a different story.  Try this stuff first, and if it isn't your problem we'll look at the injectors.

Jason

[TurboGTU]

You stay up late too. well its 2:33 and I am calling it quits already. Me go sleepy time now.

[turbo90gp]

Well the temperature has warmed up a tad outside and the idle while in gear is still higher then what it used to be and my gas mileage has gone down considerably.  I hadent touched anything under the hood when it started doing this, it started doing it before i hooked up the MBC

[TGPilot]

Just curious, but is your Windshield Defog on when you get the high idle? Depending on which version of TGP code you are running the IAC is set to increase the Idle at start-up if the A/C or Windshield Defog is on. If I am reading things right...it is called IAC steps added at start-up if A/C on. As you might already know that when the Windshield defog is on it runs your A/C pump.

AUAF increases the IAC steps by 6
AZRC increases 0

Next time your idle is real high, select only heat or vent (not mix) and see if your idle drops. Just a thought... 8)

[turbo90gp]

tried it and nope, still high... I went from 19.9 MPG to 13.1 MPG...WTF?!?!

[mfewtrail]

one of my vacuum lines under my plenum on my NA 3.1 was broke on my GP and it would idle at about 2K rpms at random on start up, after replacing the vacuum lines, it hasn't happened since, also I had no SES light or any trouble codes showing from this........might wanna check em out.

[eclipse5302]

Could be leaking injectors.  From a previous post:

In fact, I think more injectors are leaking then people actually think (or want to admit). If anyone has these problems...it could be a leaking injector(s):

-Bad fuel economy (assuming no other econo problems like O2 sensor)
-Idles higher than normal
-Spikes in idle speed due to fan turn-on/compressor turn-on/putting the car into park or neutral
-Overall weak idle (goes real low when putting in to gear)

Now, people can have these problems and have it be something else, but 75%-95% of the time it's cause of one or more bad/leaking injectors.

This could be it, and would account for the decrease in economy.  If you want to check, remove the upper plenum, and unbolt the fuel rail (with the lines and injectors stil installed).  Flip it over, and prime the rail (use red fuel pump prime wire next to the + battery terminal block...connect it to the battery terminal to turn on the fuel pump).  Once the rail is primed, disconnect the prime wire and let it sit for a while, upside down.  After about 10 minutes, look into the hole of each injector.  If there is a small puddle of fuel, the injector is bad.  The hole should be DRY.  With my TSTE, I've had a used set leak, and I had a new GM set (about 8 months old) leak.  I replaced them and it runs great now.  

Multitec injectors are prone to leaking.  I've replaced the stock Multitec injectors with a set of Pintle injectors.  These don't leak as easily.

Jason