Question about Startup A/F

[TFZ_Z06]

Running CL with MAF:

COLD START(EX: 60F)
A/F stays below 14.7 until it goes CL, then behaves normal in CL. The idle is really good. If I rev the engine and let off it never dies. Its very stable. There is no surging, bucking or anything else. In fact, the engine has very good manners and runs good at part throttle/idle.

FROM A WARMER START (EX: 120-194F; has a 192F thermostat):
The engine goes lean (~19+:1), but of course as soon as OL times out and we are in CL, it stabilizes to ~14.7:1 and runs like above. I forget what the A/F looks like stock at warmer startups.

Any suggestion(s) for what I should check out? If you have experience w/this issue or an idea, please post. Would be appreciated. Note, I am trying to figure out why so lean from warmer start ups till CL.

[WeathermanShawn]

Assuming it is not a false lean..wideband vs narrow-band O2 voltage.

1. Is your Commanded Fuel in Open (Cold) Loop Table stock (B3605)?
2. STFT & LTFT trims enabled?
3. O2 Switchpoints stock (B4105).

Running closed-loop MAF, the few lean start-ups I had in summer..Re-did VE idle fuel (simply added 10% more). Also, increased desired airflow. If all those tables are stock, richen it up, and see how the trims respond.

[TFZ_Z06]

Assuming it is not a false lean..wideband vs narrow-band O2 voltage.

1. Is your Commanded Fuel in Open (Cold) Loop Table stock (B3605)?
2. STFT & LTFT trims enabled?
3. O2 Switchpoints stock (B4105).

Running closed-loop MAF, the few lean start-ups I had in summer..Re-did VE idle fuel (simply added 10% more).

Also, increased desired airflow..Slightly above my total understanding on exactly how STFT's correct via airflow, but that helped.

If all those tables are stock..richen it up, and see how the trims respond.

Hope that helps.

..WeathermanShawn..

A small copy of B3605. My engine idles around 60-65kpa. Whats strange is when I startup fairly cold (eg, 60F), the A/F pretty much matches the data below.

I guess I better check for air leaks. Something doesn't seem right.


SNIP OF B3605:
ECT 60 65
32 11.467086 11.345924
50 11.855954 11.726481
68 12.707818 12.232180
86 12.761757 12.465464
104 12.882047 12.761757
122 12.893095 12.893095
140 13.592540 13.494927
158 13.592540 13.494927
176 13.592540 13.494927
194 13.592540 13.494927
212 13.592540 13.494927
230 13.592540 13.494927
248 13.592540 13.494927
266 13.592540 13.494927
284 13.592540 13.494927

[mr.prick]

does "WARMER START" have high IAT`s?

[TFZ_Z06]

I'm driving it to work today so I can run an IAT log. The outside air is cold < 50F lately. 39F right now.
I wonder if the airpump could cause this much of a lean condition. I'll be turning it off as a test.

[SSpdDmon]

Well, yeah - if the AIR pump is active, it will read 19:1 AFR's easily. At least, that's what I saw with mine when I first started tuning. Freaked me out! But, then I shut it off. What gets me is it doesn't do it cold. So I'm wondering is A) the AIR pump not running on cold starts or B) is it running and you're pushing way too much fuel?