LS3 does not idle

[vstol]

Were the wires frayed??

[Neil B]

Originally Posted by vstol

Neil its a Blue Print Engine 427 FI with a MAF, specs are on their web site. I am told it needs to be running on the road so the ECM can adjust and it will not do that sitting in my garage. I have corresponded with another who has the same engine and it took about 25 trips to settle out,. That said I am not sure I drink the cool aide but Blue Print Engines is waiting for it to get on the road and go from there. The engine has been dyno'd so I am not sure...

It seems the likely culprit is the IAC. However the cam in your engine appears to be a 239/[email protected] 114 LS which is pretty big for an LSx MAF tune if you are running the stock ECM. These engines are pretty sensitive to base timing and MAF curves with bigger cams. If you are running a stock ECM, it's really only the fuel trims which will learn/adjust and even that is pretty minimal. Good luck and let us know what ECM you are running.

[vstol]

They and I are running the stock ECM. How do you test the IAC? Thanks

[71RS/SS396]

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

If this is DBW the ecu will open and close the tb as part of it's start up procedure. DBW has no IAC, the throttle blade is used as the IAC. It sounds like the tune is really jacked up, usually an unmetered air leak will make it idle high.

[vstol]

Thanks Will check for air leaks again and make sure I have all the vacuum lines going or capped in the right position.

[dhutton]

What did you do for crankcase ventilation? Where is the MAF installed relative to the throttle body and bends in the intake tube?