High Idle - Tune Software Seeing 2 Different ECT Values Simultaneously
I just changed the 97 dually in sig over to a 12212156 based COS5 (based on the current tune on my 1500 in sig) to replace the 2001 OS I had been using with COS3. I wanted the TCC to stay locked on a lift and my 4lo to function correctly as they did with my 1500. No issues flashing it over, but I did sneak in 1 change: I found lower desired idle speeds than I had been using on another stock 454 tune and plugged those in. With that, I figured desired airflow would require a change so logged calculated airflow at an idle to see how far off it was. It's so far off I wonder if I even looked at it last winter? I thought I'd done both trucks but I guess not. Desired airflow values are not my problem though, my problem is this random high idle I get and today I wonder if it didn't shed a bit of light on the issue? Check out the observed coolant value in the tune software on desired idle speed. This tracks with what the gauge display was showing in the scan tool.
Now check out desired airflow, this one's out in left field.
Yes one is in F(reedom) and the other in C. And here you can see airflow trended the wrong way as the truck warmed up.
Thing was idling at 1150 when it should have found its way down to 575. I came in for a little bit, then went back out for a test drive and the idle seemed to have settled back where it should be. TCC and 4lo did their thing, so I'm happy about that. My suspicion was that the truck in 1 respect thought it was hotter than it really was and ramped up the desired airflow accordingly, it tracked fairly closely with that. Here's the tune and the log.
Dually COS5 Post COS5 Pull.ctz
Dually COS5 Idle Log 1.efi
VE, MAF, timing, etc were procured from the COS3 tune. I still intend to verify all of it in case I missed something, but it fired and drove the same as before so should be pretty close to what it wants.
Reply With Quote