Hello,

I have a 73 c20 pickup that i converted to EFI. I swapped in a LO5 and 700R4 from an 87 suburban, converted it to SD TPI , controlled by a EBL P4. Motor is stock with 24# injectors, Thorley tri-y headers into a single 3" exhaust and I am using a heated O2 sensor. I am having trouble with an intermittent surging idle in closed loop. I think my cheap O2 sensor may be at fault. I played back a datalog I made this morning and the O2 sensor reading seemed erratic. I am hoping someone can confirm if it is behaving correctly or not. The surging idle is at the end of the datalog. Sorry for the long post. James

Seems my datalog file is too large to post. Any way to edit it to make it shorter?

 

Need to add to the proportional gains. Notice that the INT is slowly going up and then down. Due to a lack of prop gains the ECM is using the INT to force cross counts. Which in turn is causing a large over & under shoot of the AFR. That is what is causing the idle to oscillate.

Add to this table in the area of 16 gms/sec airflow:

PRP - Duration vs O2 Error

That table may already be near maximum, if so halve the table values, add to the 16 gms/sec area, and double the values in this table:

PRP - Gain vs O2 Error

RBob.

 

RBob,

Thanks for the reply. I looked at the datalog again and think I understand what you mean. Since the truck consumes approximately 16gms/sec of air at idle, I need to adjust the PRP duration in that area. Unfortunately unless I am looking at the wrong tables the values are listed in O2 mV not gms. Would I use the PRP- Gain Multiplier vs Airflow? James

 

Yes, you are correct, I posted the wrong table. Too early in the morning...

PRP- Gain Multiplier vs Airflow is the right one to adjust.

RBob.

 

RBob,

Thanks again for your help, understand how mornings go sometimes. Will play with it this week see if things improve. James