For some reason I can't seem to nail this down. It was working ok until it started getting into the teens and 20s at night. Running the stock open loop AFR table I am having a rich condition on startup and for about 30 seconds to a minute after that. Its wanting to command 11:1 at startup which I know is too rich, and my engine says is too rich judging by the roughness and rich fuel smell in the exhaust. If I'm understanding this correctly the AFR Reduction at Startup vs Coolant Temp (Choke) table is meant to richen the open loop table at startup correct, hence the term choke correct? If so I've tried slowly bringing the choke AFR's down to as low as 2.5 in the area its running on cold startup and I'm still seeing AFRs of 11:1 in park and 10:1 when I put it in gear. If I'm understanding this right lowering the choke AFR should essentially lean the cold start mixture out correct? If so why aren't I seeing an overall ratio of 12:1 on startup if the cell its running in on the open loop table is 14.5:1 and the choke is richening by 2.5:1? Personally I'd like it to run around 12.5:1 and then quickly lean towards 13+ and then hit closed loop but so far its not wanting to do what I tell it to. Any ideas why its running richer then what its set to run?

 

What are you running, what mods give us all the
details,

 

Vortec heads and vortec carbed spread bore intake with the 87-92 454 heated adapter and 454 throttle body, mild comp cam, long tube headers into true duals with no cats and a single 02 sensor in the passengers side pipe about 2 feet behind the collector.

 

maybe adjust your CTS vs AFR for open loop table a bit. make it a tad more lean in the colder temps. I'm not sure how it's expressed in $0D (if that's right) but I've had good results changing my equivalent table in EBL for that since the temps have gotten real cold (mine was running too lean when below zero F, had to richen it up a bit). I didn't need to change it much at all, but it needed it. 15.1 AFR on fire up at 1100 rpm is too lean when it's -15F deg ambient

 

Just talked to Fast and he said the same thing. The choke table vs coolant temp was just too rich in the colder temps. Now that I know how it works I'll keep toying with it and see how lean I can get it and still run alright when its cold out. Trying to save fuel here and I know letting it chug and flood when its 15 degrees out is not a good way of doing it.

 

you need to hook me up with the Fast 305 "red phone" you seem to have LOL

 

Its called AOL messenger but I've also got his number too.

 

I'm having the same cold start issues. There is a table in $0D at address 4BA3 that deals with the AFR at idle. From what I understand it deals with the leanest the AFR is allowed to be in open loop at idle. Adjusting it seems to have helped me. You may want to give that a try.

 

I think I've got it figured out. At cold temps the open loop table is just richening up too fast when there is low vacuum, ie cold startup. I think the 15W 50 mystic diesel oil isn't helping things either.

 

Finally figured out what I was overlooking. The open loop idle table was still set to command the rich AFR's I was getting at low coolant temps. I didn't realize it was doing that or I would have noticed it earlier.