Old school AFC (single knob) and wideband question??

[casing]

I have an 87 7mgte supra. The previous owner installed an old school AFC with the single knob. He had an exhaust gas temp gauge but I recently installed a wideband something I understand a little better. Now I'm having a weird intermittent problem with my fuel ratios. Sometimes it runs 14.7 at idle and cruise and I can adjust the single knob afc and make it really lean or really rich if I want. Then other times the car will not go leaner then 14. I can turn the knob all the way to full lean which is -10 on the AFC and it will not go past 14.0 at idle.
Does anyone have an idea on what I should do or where to start?

 

[jetjock]

Stop fighting the O2 sensor?

 

[casing]

Sorry for being a noob. Like I said I'm trying to figure this out.
i guess I'll try something tonight then.

 

[casing]

Alright I'm going to explain my problem in more detail. It seams to only happen after cars warm and a key cycle.

I can get into my car on a cold start and drive it as far as I want for as long as I want and my air/fuel ratio is perfect. As soon as I turn off the car and start it again, I'm running rich as hell unless I let it cool down. On that first key cycle when the cars cold it will run a perfect 14.7 at idle and cruise even after it warms up and I've been driving for 50+ miles. Im new to this stuff and don't know where to look. I tried disconnecting the stock O2 sensor but it's still exactly the same.

 

[jetjock]

You're trying to tweak things when the system is in closed loop which it always is at part throttle with a warm engine. It's done for emissions reasons but that's a good thing it also happens to be where the engine runs cleanest and gets nearly the best fuel economy. You should worry more about getting the mixture right at WOT. As for the WB it measures O2, not AFR. The EGT is superior in some ways (one reason it's so common in aircraft) but as you said a bit of learning is required to interpret it correctly.

 

[casing]

My aem gauge says air/fuel ratio written on the box and on the gauge itself.

I do not understand what you mean Jetrock. Let me just give you this example to show you why it doesn't make sense.
If I leave my AFC dial on, let's just say 3 to make it easier to explain, and drive my car in the morning my reading on my "O2" gauge/air fuel ratio gauge reads 14.7. I drove for 100 miles, so clearly my engine is warm, my gauge still reads 14.7. i pull over to piss, shut off the car, piss, then get back in and start it up. I don't touch anything on my AFC it's still at "3", start driving and now my gauge reads low 12s and stays there for the rest of my drive to work. no "tweaking" took place, so what happened?

 

[jetjock]

Codes? Sounds like you may have a cross counting problem with the stock lambda sensor.

Your AEM displays AFR but the sensor itself measures nothing but oxygen. EGT measures the variable (temperature) directly. That's all I was getting at.

 

[casing]

Sorry if I come across as a dick. I'm understanding more and more each post I read and make. I am just going to follow the flow chart for diagnosing the O2 sensor and see what happens. Thanks for your help.

 

[jetjock]

It's OK because, ya know, I never come across as a dick here...

 

[casing]

I thought I would try another O2 sensor but it does nothing.

If I leave the O2 sensor disconnected the car does the exact same thing. It shows no codes for O2 sensor and it runs exactly the same (rich only after you turn the key off then back on again)

If I unplug my afc and start the car the wideband shows 10 and O2 sensor code shows up.

Jetjock said what only matters is my wideband reading at wot. Well when I idle at 13.8 what do you think my wideband shows wot? Rich as fuck, in the 10s.

 

[jetjock]

Any other codes? Best thing at this point is to return the engine to stock (disconnect the AFC) and see if the engine is able to do normal fuel control (14.7) at part throttle. If you're not trusting of the WB then check cross counting of the NB per the TSRM. Better yet is to measure average NB voltage at 2500 rpm.

 

[Nick M]

Stop fighting the O2 sensor?

Depending on whose book you are reading (I am thinking of one in particular) the wideband's purpose is greater feedback control. So I don't see fighting it either.

It's OK because, ya know, I never come across as a dick here...

Only in the land of giant assholes?

Well when I idle at 13.8 what do you think my wideband shows wot? Rich as fuck, in the 10s.

If you still have the factory installed TCCS operating the injectors, that is normal and it is supposed to be that way.

 

[casing]

Thank you for letting me know that Nick M.
Im wondering if I can ask you something else?
Is it normal for the car to run RICH as hell at idle/cruise after a WARM start? When I get into my cold car my ratios are 14.7 at cruise/idle, AS SOON AS i turn off the car and start it immediatly, the car will show 12's at idle without touching anything, the only thing different is I started the car warm. If I start the car cold, the problem never happens, I can drive for 100 miles and its AFR's are fine.

 

[Nick M]

How bad does it run at 12:1 on a hot restart? And how hot is Ottwa? Is that the same as Ottawa, Canada?

 

[casing]

I never have left it that rich. I always adjust my AFC to the max lean it can go can I idle around 13.6-13.9.
Before a warm start I can adjust my AFC to run lean as i want or rich as i want. After warm start Im ony limited to how rich i can run.
I do notice a slight loss of power when driving aggressively and running that rich. In Ottawa it's usually between 25-30 degrees Celsius. A lot of the time it's so fucking humid here also.

 

[casing]

I just need to know what the ECU looks at to adjust fuel ratios. I am going to check my cooling temp sesor today and wiring. Is there anything else I should look at?