Commander 950 911!!

[JimM]

911-911 Anyone home tonight!!!
Sorry for the long post, trying to give as many details as possible.

Fired up my c950 tbi for the first time today. She started right up, wouldn't idle, running lean, not unexpected.

After firing her up 2 or 3 times this afternoon, I went in search of a better map. I downloaded TBI6 which seemed to be a better match then what I was using. I entered the voltages for my autometer wideband and changed a couple other things in engine parameters, saved the file to disk, and flashed the ECU.

Twisted the key, she fired right up, let her idle for 2 or 3 minutes. She sounded good, but was surging up and down in rpm maybe every 10 seconds, a several hundred rpm change.

I was running with timing control bypassed. Since it would idle, I figured the next step was to set ignition reference, and give the ECU timing control. I physically set the timing to 10 degrees with a timing light. The idle steadied out when I backed off the timing.

She was idling at 16:1, so I figured I'd fatten her up a lil. Noticed the cursor was on the bottom (100) cell??? MAP digital readout was 48, and was responsive to the throttle!!!

So I fattened up the cell she was idling in. "Active cel" moved 1 to the right, so I fettened that one too.

About that time she gave a loud backfire thru the exhaust and quit.

I pulled up engine parameters, and saw that the load scale, battery voltage scale, and a bunch of other stuff were ALL ZEROS.

About that time I got a RUN TIME ERROR on my screen and the software shutdown.

I turned the ignition off and on again, and restarted the software, still all zeros. Opened my saved map from disk, flashed the ECU, twisted the key.

The engine WILL NOT start. She cranks and cranks, but no fire.

[camcojb]

sounds ignition-related. Make sure your signal wire from the ignition to the ecu is connected and working. If the signal works then I start to look at the distributor/module and coil.

Jody

[JimM]

Found the data in the ecu was corrupted. After a couple failed attemps to reflash, I did a "force default values" which returned things to normal, then successfully flashed my map into the ECU.

Still wouldn't start. Spark was good, but there was fuel on the throttle blades. Tried cranking her over with my foot on the floor (clear flood) and she sputtered to life.

[69bird]

Best forum for holley fi is www.chevytalk.org. There is a member on there that is a engineer for holley.

[JimM]

Originally Posted by 69bird

Best forum for holley fi is www.chevytalk.org. There is a member on there that is a engineer for holley.

I'm posting there too, and have gotten help.

I got my corrupted table straightened out and reloaded, car is running again.

Also discovered swapping the 5 & 7 plug wires causes some real loud backfiring...lol.

I now have a "kinda stable" idle. Still in open loop with timing locked out at 30.

Mixture was rich, 10:1 showing on the autometer wideband. I started leaning out the entire table by 10% at a time.

As I got leaner than 13:1 the idle started hunting around a lot.

Currently at "Average" 14.3:1, idle hunting from 900 - 1300 rpm, with some slight misfiring going on.

Any suggestions on where to go next appreciated.

Considering:
1: work on my son's pinewood derby car for a while.
2: readjust the valves.
3: Set static timing to 10 degrees and give the ECU timing control.

In case anyone wants to watch, my Garage Cam is on.
user id is "team"
p/w is "camaro"

[camcojb]

Is the cursor hitting several boxes? I generally try to get the entire idle area blocked out until I get the idle where I want it. In other words, it may idle mostly in one cell, but the cells surrounding it will all be highlighted and changed as one. If it even touches the edge of another cell it's "borrowing" the numbers from it, which can cause wild rpm swings.

I like to allow the computer to control the timing, especially at idle. I get the a/f right first. By the way, a thought on this. Do not get hung up on the numbers. Your particular cam/intake/engine combo may not be happy idling at 14.7:1. Give it what it wants, it will make settling it down much easier. Many of my engines would not idle happily in the 14:1 a/f range, yet you richen the idle to say 13.5 they were noticeably smoother, vacuum came up, etc. Give them what they want.

Back to idle timing. Once you get the a/f to a happy spot, with all the boxes the same number that it's hitting, start on idle timing. I usually want at least 20 degrees at idle in the main timing map. Again, keep all the boxes it's idling in the same, as if it hits a box with a higher timing number it makes the idle speed fluctuate. I also like to let the computer use timing compensation at idle, up to 8-10 degrees usually depending on how far off the actual idle rpm is from desired. This really steadies the idle rpms.

One other thing, once you have the engine up and fully warmed, you need to set the throttle blades properly, or at least verify that they are set properly. With it fully warmed shut off timing compensation at idle, and command a real low rpm number, like 500 rpm. This will force the idle air control to shut fully and the only air holding the idle speed is the throttle blades. Set the blades to hold the minimum idle speed you want fully warmed, just like with a carb. Reset or check your tps setting as it will likely move. Then turn the idle timing compensation back on, and re-enter the correct idle speed in the computer. Now you have full use of the iac which can help tremendously with idle speed fluctuation. If the blades are not open enough the iac is having to be open too much just trying to get your desired idle rpm, and is useless for what it is supposed to be doing. This is very common.

Jody

[JimM]

gotcha on TC Jody, thanks.

I'll richen her up until she stops hunting around, then let her get all the way warm, I've barely let the temp gauge go over 150 yet.

Then I'll set the reference timing right and give the ECU timing control.

She used to idle at 14.5:1 smooth as a cadilac, 'course that was with a carb, different heads, different manifold, and a hydraulic flat tapet cam with 7 flat lobes!