I have an OBD1 383 LT1. Car has been tuned and I have access to Tunercat and scanning software.

I've always had problems with a rich Idle at closed loop as many of you have experienced.

I locked the BLM's at Idle at 128 and the problem (after some tweeking) is gone. Another problem has started bothering me though.

When I first start the car and am in Open Loop, the car runs extremely rich... the IAC shoot to 160 and of course, any time I put a load on it by placing it in gear, it dies unless I rev it to get it going.

I've adjusted the Startup AFR and Open Loop AFR tables, decreasing the amount of fuel.... but no difference.

What my theory is, is that while my BLM's are locked closed loop at Idle, the integrators are reading high, and the computer is remembering it for the next startup when the car is in open loop.

Any thoughts? What can I do?


Thanks for you opinions.

 

Here's the thread I found and used for mine. It works pretty good. Gotta watch if you get too much timing and lean idle the Nox increases and burns your eyes. You'll know what I mean if it happens. Are you running catalytic converters?

http://web.camaross.com/forums/showt...light=idle+blm

 

not sure on your issue specifically but that's interesting if your analysis is correct. I always thought that on startup only the open loop afr table is used and there is no dynamic data used.

 

Your IAC shouldn't be reading that high. You probably need to open up your TB Blades a pic and get those IAC readings down. What are your IAC counts at when the car is fully warmed up and at idle? They should be around 35-40

 

The reason the IAC's are so high is that the car is dumping in more fuel than needed and the car is trying to add air to meet the demand.

When the car is in closed loop, IAC's are in the high 30's to low 40's.



As for using only the open loop AFR at startup.... I've taken out a lot of fuel.... it worked well on the first startup and I thought the problem was resolved... however, after a litte driving, the startup issue came back.