Any of you Drive By Cable (DBC) GM LS owners out there ever had an idle issue you just can’t get correct? Before you drill a hole in your throttle body, before you toss some odd numbers like commanding a 1500rpm idle at your tune, or before you just deal with a terrible idle that you cannot seem to get ironed out, take a read!
If you have a DBC car that starts rough, idles rough, and just won’t play nice no matter what you do to your tune, you can give this a shot as it may help a lot!
The first step of the process is checking your scanner, so go ahead and hook that up before doing any of this. Get your scanner connected to the car and turn the Key On, Engine Off (KOEO). TPS should read right around 0.4% - 0.8% for best results here. During WOT you should be able to get at or over 99%. If you do not hit these marks you can experience issues.
1 - Turn the KOEO, while viewing your scanner, adjust your throttle body set screw until your throttle position is 2%
2 - Turn your key to the OFF position, disconnect your scanner
3- Head out under the hood and unplug your (TPS) and Idle Air Control Valve (IAC)
4 – Head back into your car and turn your KOEO, wait 30 seconds like this. After 30 seconds, turn the Key back off.
5 – Back under the hood, plug the TPS and IAC in. Head back into the car and turn the KOEO, connect your scanner.
6 – Your scanner should now read 0-0.8% range even though you added that 2% opening to it. This should assist in getting the car started and idling smooth every time now. This process may take a few shots, so don’t give up!
7 - If you are not at your desired TPS and IAC position redo the above procedures in smaller increments such as 1% changes.
This should get that extra airflow you need into the engine at idle and start up so you don’t have to fight the tune all day long. If you tune a lot of GEN 3 GM stuff, this can greatly assist!