Turn off all IAC functions.

**chris989** · 12-31-2018

Don,
You are right, My guess is a faulty wire of sensor. everything is new under the hood but I have had plenty of defects out of the box. The next time it is idling right, I need to log and make a spreadsheet. Then log again when it is acting up and see if i can find the variable.

My TPS and MAP never give me erratic signals that i have caught. THe TBI set up is so simple, I can not believe i can not find the source of my problem.

Thanks,
Chris

**chris989** · 01-27-2019

Hello again,

I have been fooling with Tuner Pro and loggin some data. Nothing in my data shows a MAP or TPS issue and the truck is running smooth. I have concluded closed loop for AFR is not the same as closed loop for idle?? My truck goes closed loop easily with the heated O2 sensor but i feel the idle logic is OL. Attached is a screen shot of the scalars that make very little sense to me.

Open loop RPM theshold is on at 1600RPM and of at 1500??
closed loop coolant cold timer at 200 seconds?
Why is there a cold and warm coolant threshold? why not one setting where it goes from OL to CL?

What do the timers delay?

Any help would be great.idle logic.jpg
CL coolant warm timer?

**stew86MCSS396** · 01-27-2019

I think you're stating it backwards. Yes with those parameters, it appears you have OL idle bin. If you read enough on this forum, some say they don't like OL idle and prefer ECM controlling with CL idle. I think the tuning strategy for using OL idle is if you're running a radical cam that produces low vacuum.

**chris989** · 01-28-2019

I am trying to disable the open loop idle or have it go closed loop earlier. Today it is back to high idle. I am sure it has something to do with the steps added in OL idle. The truck is in CL but the idle still goes open sometimes.

I will try to zero them one at a time when the motor is cold and see if i can affect a change

thanks,
Chris

**sturgillbd** · 01-29-2019

Make sure your P/N switch is sending the input to the ecm. Also make sure your vss is operational. If I remember correctly, the 7747 needs both for the idle to calm down. A friend put tbi on a 1975 jeep with a sbc. We ended up grounding the P/N input to the ecm because he had a manual trans and the idle would flare up in the woods as you describe. He would end up shutting engine off and restarting to stop the high idle. He didn't have a vss connected and it seems like those ecm's need it. Just something else to check...

Brian

**chris989** · 01-29-2019

Originally Posted by sturgillbd

Make sure your P/N switch is sending the input to the ecm. Also make sure your vss is operational. If I remember correctly, the 7747 needs both for the idle to calm down. A friend put tbi on a 1975 jeep with a sbc. We ended up grounding the P/N input to the ecm because he had a manual trans and the idle would flare up in the woods as you describe. He would end up shutting engine off and restarting to stop the high idle. He didn't have a vss connected and it seems like those ecm's need it. Just something else to check...

Brian

BINGO,,,, I just went back and looked at the raw data and the raw MPH is zero. It is interesting what you said about turning off and restarting. I notice that it will be high and then i turn it off and restart and life is good.
I originally had a 400 turbo but switched to a 4l80. The trans is run by an MSD controller so the original set up is not hooked up.

What did your friend do about the VSS signal?

Thanks for the lead, I will look into how to get the proper signal from the 4l80.

Chris

**sturgillbd** · 01-30-2019

We just grounded the P/N pin and it helped a lot. With you having the 4l80, you can hook up the drac and send the signal to the ecm. Should be able to parallel the VSS signal from vss to the drac and the controller. You may be able to get the signal for the controller directly from the drac. What VSS signal does the MSD controller require? 40 PPR or 2 PPR? See http://gearhead-efi.com/gearhead-efi/doc/DRAC2.pdf for a pinout of the drac. Newer models are similar.