Troubleshoot surging at idle

[only_1]

I have came in late in the game obviously. If you have 80lb injectors and running them at 20psi, you have approximately 100lb per injector and you may have a little too much injector. You can try to lowering the minimum BPW times under BPW Limits. I don't know how much it will help you. I am running 61lb/h injectors at 27psi currently and idle fueling seems ok. Can you lower your fuel pressure? If so, you may have an easier time tuning this thing. Another thing I noticed is not a lot of spark advance at cruise. How heavy is this vehicle? I'll look at your bin this evening when I come back in.

Brian

Yes, I can adjust the fuel pressure to be lower if that would help.
The truck is a 1994 Blazer Fullsize. I think its around 4600 lbs.
The spark map was something I got from Fast in my other post. I have not changed it much since I got it from him.

[only_1]

I am going to start over with setting the throttle body blades to idle with IAC closed when hot. I wonder if that isn't the part of my problem. Either way, some times its best to start over at square 1.

[sturgillbd]

Twist throttle screw clockwise 1/4 turn. Look at IAC counts. Adjust only when hot. Keep turning clockwise until counts drop to around 10 or a little below in park. Shut off engine for approx 10 seconds (until PCM fully powers down) then restart. See what your counts level out at after a couple of minutes idling. Your counts weren't extreme but it needs a little more air past the blades. This helps the fueling at idle due to shearing action of air going past the blades. I am downloading your bin now and going to look at a few things
Brian

[sturgillbd]

Your datalogged spark doesn't match what is in the bin file. I have been trying to find what is causing the commanded spark advance to be lower than what is in the tables. Most places I checked it was off by approximately 5 degrees . I also notice your egr is commanded on the whole time the vehicle is running. I will dig further as I get time.

[only_1]

There is no egr on the truck. It is plugged off.

[only_1]

Would a vacuum leak cause these problems?
If the EGR is always on, in the program, it would mean that the EGR spark correction would always be on right? So that would be the 4 degree drop in timing?
-I zeroed this out for the next run to verify this, in addition made changes to try to disable EGR in general.

[sturgillbd]

Don't think you have a vacuum leak. Something is commanding the egr on and it seems like you have it disabled by scalars. I did a bin compare between your bin and BJYL and found several differences outside the defined parameters. You may need to start with a fresh copy using your timing tables etc .

When replaying your datalogs, do you see the EGR being on all the time?

Brian