[Gmecm] Idle Speed

[jryan at caminofx.org]

Well, I did some data logging, and the logs are at home, but I  
remember enough to be useful.

(To refresh: GM long block 350, Crane Cams 2032 roller cam, TBI,  
overdrive, Chevy El Camino, '89 9C1 Caprice 350 ANLU PROM.)

The "target idle speed" in the ECM is about 560 RPM.  The ECM seems to  
want the engine to idle at 875 RPM.  The TPS shows either .41V or .36V  
at idle (why is it different at different times?  I know my foot was  
off the pedal).  The IAC counts are always 40 at idle.

So it looks like the ECM is commanding it, but I don't know why.  By  
the way, the maximum hot idle speed set in the PROM is 900, so I doubt  
that the 875 value is a coincidence.

I am able to get the engine to idle at 560 RPM if I unplug the IAC  
motor.  The ECM is definitely commanding this relatively fast idle.

Another thing I noticed is that I'm running fairly lean.  The BLMs in  
all cells that updated were 137.  I have the 9C1 PROM, but the  
full-size pickup 350 injectors and stock fuel-pressure regulator.

It was suggested to me a while back to bump the fuel pressure to 15  
psi, but at the time, I didn't know I had a leaking injector O-ring  
and it made the car belch black smoke out the pipes.  I am going to  
put the adjustable FPR back in and raise the pressure as soon as I can.

But what I am asking is if the running lean and the fast idle could be  
connected.  I know on a carburetor, a fast idle is often due to  
running very lean, due to a vacuum leak.

What's interesting is that I just drove around the neighborhood, but  
all the cells that updated were right about 137.  It's definitely a  
bit lean.  It also pings ever so slightly on acceleration.

I can supply more hard numbers from the logs when I get home.