Idle problem

I was going to say try adjusting your idle screw but you said you already did that. I have the same problem intermittently right now after my custom tune with chip. It doesn't do it all the time, but it surges then drops like you said
yours was doing, just not as bad. I heard that if you unhook the negative battery terminal and let it sit unhooked for a few minutes and then rehook
it up the computer runs thru all it's checks again. I've heard sometimes that
works. My "Service Engine Soon" light came on a couple of days ago out
of the blue, my car was running fine, and it would not go off. I did the
battery trick, and it hasn't come back on since.

OK, I have been messing with an idle problem for WEEKS, but finally got it figured out. Do you also have an after-market TB and plenum? I am going to tell you what I learned:

There are many things that affect idle speed and consistency. Mods like yours can really dick things up, but it is all fixable.

1 - Do you know what the IAC is? It is located on the front of the plenum. There are two screws on it that attach it to the plenum. There is a black hose goining to it that comes right off your air inlet pipe. There is a black platitic box right in the line. You can't miss it. The IAC (or idle air controller) allows air to bypass your TB when your TB is closed. Many idle problems are caused by dirty IAC's. Dirty IAC's will not open or close properly. Since your problems did not happen until you installed a mod, the C&L, I would assume that your IAC is clean, but you never know.

Because it is simple enough, clean it any way. To do so, remove it. Then spray some intake cleaner in it. BE SURE TO USE SOMETHING APPROVED FOR TB's. Be liberal with the spray and swoosh it around a lot. You will see some carbon in it, this is normal. The cleaner will work like a charm.

Then, re-install.

2 - Next, set your base idle!!! To do this, remove the electrical wire that is connected to the IAC (or just leave it removed from when you cleaned it). Then, start your car. If the base idle is set correctly, the car will not stall! If the base idle is set correctly or too high, the car will run with the wire removed. If the car runs, very slowly turn the idle screw back until it starts to bog. Leave the screw set just at the point where the car still runs. If the car dies, then do the opposite. Each time adjusting the screw and then restarting. Now, your base idle will be set.

In the process of doing this, your check engine light will come on. Don't worry about this.

3 - Reset your computer: Then, disconnect your battery for as long as you can. It will be best if you can do this overnight, but some people think that 30 minutes is fine. I would let it sit over night if you can. This will drain all of the bad memory from the ecu from you messing with the idle out of the car.

4 - Connect the battery and start back up. Let it idle until the engine is completely warm. Don't expect miracles right away. Your car has to relearn the new settings. Then, turn on all of your accessories for a while. Then turn off for a while. Let is run for a total of about 20 - 30 minutes if you can.

5 - Now you need to drive the car. It may take as much as 300 miles before the car will completely correct itself, but it will.

6 - TPS: Another problem you could have is with the TPS (Throttle Position Sensor). I doubt this is the case, as you have not messed with it. But, if after doing the above mentioned and is still running all over the place, then we will need to replace the TPS and reprogram the car again. If you want to avoid this problem, you can always just replace the TPS now, but I wouldn't.

You can email me at bschomas555@epix.net if you have more questions or would like to talk on the phone. I will give you my number in email, but not post on the thread.

Let me know how this works eitherway.