Well, since I've added the wideband, Ive been data logging and every time I do a cold startup, it went way lean, at least 2-3 full points leaner than commanded AFR. Just and FYI, I have the fuel trims turned off and I'm in SD open loop since I'm tuning the ve table by AFR error%.

The odd thing is if I let it warm up, the idle will actually richen according to the wideband to finally meet up with the commanded AFR. I noticed today that at the same cell, same map kpa, it has the same injector pulse width the whole time. The only change is the wideband reading. So it's not a change in fueling that is effecting the afr readings.

My theory is this, since I have long tubes, it takes some time for them to reach temperature as well as the wideband O2 sensor, causing a 'false lean' if you want to call it that.

Does that make sense??

 

Mine does the same thing. I believe if you log the IAC counts you should see a higher # at startup, this adds more air causing the lean condition. When it runs lean it warms up faster. I can get mine to startup at the desired afr, but it runs like crap.

 

I hadn't thought about the IAC counts, but that does make sense. Granted, it's still drawing the same amount of vaccum, so it doesn't make too much of a difference.

Just thought I'd see if I was on target or if I had a tuning issue.

 

you sure its not just the wideband warming up.. I always fire my wideband up for a couple of minutes at least before bothering to start logging. Narrow band sensors suffer the same thing.

 

Maybe the airpump

 

Also a cold engine isnt going to burn as completely as a warm one, fuel charge will not vaporise properly and will remain in suspension more when cold. This will mean unburnt fuel is heading out the exhaust and making it look lean.

 

Well, it's not the airpump, that was removed a long long time ago.

Ringram, unburnt fuel makes it look lean? I think it's the other way around, unburnt fuel would mean that it's running too rich.

 

I am having the same issue, any updates on this?

 

The O2 sensors only see O2 - if it's not burnt up in the combustion process, the reading will be lean. If a plug goes dead or misfires, the O2 that's pumped into a cylinder during the intake cycle is pumped right back out during the exhaust cycle and will read on the O2 sensor - irregardless of how much fuel is in the exhaust pipe.

The same holds true for both widebands and narrowbands.

Bird

 

This is something I noticed after my wideband install. I asked the same questions @ EFI Live & it appears to be "normal". Nobody really knows what programming in the PCM causes it. Some guys believe it's a cat light-off function to get it heated up faster.

 

I have the same issue and I've just ignored it because it goes away eventually. My IAC counts are about 185 when teh car is lean during cold startup and the AF reaches stoich at about 165.

I'd love to have teh car start at 165 IAC count, no clue how to do that yet.

 

This is absolutely true. I had to see it to believe it. I would have thought unburnt fuel would cause a overly rich condition. I had three plugs fouled to the point they were not doing anything but filling a hole in the head. My wideband read dead lean (17:1 on my AEM). It didn't matter I had raw fuel coming out the tailpipe the sensor was only picking up the O2.

 

Common issue, appears to be just another bug in the SD portion of the operating systems IMO. Just toss in additional startup fuel adder and slow it's decay down a lot.