Quote:
Originally Posted by vstol
I have a new LS3 427 which has been run and dyno'd. When I start the car it will idle around 1500 then after working the throttle it will pass idle and want to shut off. I have run it about 15 times up to temperature and I have heard it takes the ECM sometime to sync with the engine but you need to be driving it. One thing I find odd is when I put power to the car the throttle body flips open then back to closed, is that normal? Thanks
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I'm assuming this is a factory style ECM? DBW throttle or cable? Does it idle at 1500 after warmup, or just cold?
If it idles at 1500 warm, that strongly suggests a vacuum leak, a throttle body blade sticking, or some very odd tuning. Or an IAC problem if this is a cable throttle body.
Notes: vacuum leaks will not always set a code, depending on how bad they are and how the tune is set up. Also the "learning" part of the ECM doesn't really affect idle parameters, just the fueling. And if you're using a MAF, and the engine has not been tuned with your particular air intake path, IMO you should get it tuned before running it really hard. The MAF sensor is quite sensitive to variations in the airflow path, and it is the primary determining factor in getting correct A/F ratio.