I could really use some guidance with a tunning issue.
16147060 ECM
$85

I will highlight the issue at idle, but I get simmilar problems occasionally at other driving conditions.
- WBO2 showing rich at around 10.5AFR
- NBO2 showing rich between bouncing 550mv and 800mv
- BLM maxed at 172 (set max BLM)
- Integrator either at 130 range or at 128
- Slow rich/lean flag shows Rich
- Fast rich/lean flag is switching quickly

I can not figuer out why the BLM would max out when the NBO2 is on the rich side - and the WBO2 is reading rich. At times I can watch the WBO2 start at a 14AFR, then see the integrator run up, then the BLM shoots up to 172 while the WBO2 drops to the 10AFR range.
This same scenario happens frequently when I turn on the A/C.
Drivability is pretty good outside of some surging issues at very light throttle positions and a bit of surging at idle. All sensors seem to be working well. I can not seem to tune this issue out in the v/e table. I must be missing something!

Any Help?
Thanks very much,

 

Any Help? Is my qustion confusing? I tried to make it clear, but it is a weired issue.
Help is appreciated as I am stumped.

thanks,

 

I am still struggling with this issue. I have tried quite a few programs with varying the VE table and SA table but have not had any success at solving the problem. This also seems to consitantly happen at light cruise:
I can be driving at 70mph w/ light throttle on level road and the BLM's will run up while WBO2 drops to the low 10 range.
ANY HELP???

thanks,

 

I suspect that you have a bad NBO2 sensor. Thats the one thing I can think of that would cause a high integrator number and rich condition. Is the NBO2 reading lean when the problem occurs? Perhaps check the wiring to the NBO2 to be sure that its clean. Could the sensor ground be shared with an AC system ground? O2 sensor ground should go directly to the ECM. You might try searching in the general tuning forum for other tips.

 

Thanks for the reply:
I have had the exact same situation w/ 2 separate NBO2 sensors (one brand new). The ground wire is shared with the WBO2 and is lugged to the intake, which is grounded to the battery. A/C is factory, so not sure where it is grounded.
Where would I ground it to the ECM? The stock is a 1 wire, so no separate ground wire.
Could a bad/leaking EGR solenoid cause this?

 

Have you checked your injectors to see if you have a leaking oring or bad spray pattern? Have you checked fuel pressure? Ruptured diaphragm in the fpr?

 

Yes to all. I recently rebuilt my TBI w/ all new gaskets and diaphram etc. Fuel pressure is right around 13.5.
The tough part is that I don't know if this is a tunning issue or a physical/mechanical problem.

 

CTS? Is it going into closed loop?

 

I think I solved my problem after 1 1/2 years of frustration and low MPG.
I found an unconected ground pigtail behind the motor. This has 2 wires conected to a loop ground lug. The wires are tan and black and I think they are a ground for all the senssors and TBI items.
I hooked up the ground and it is night and day better. My O2 volts are now smoothly swinging from rich to lean rather than eratically bouncing around. My NBO2 is reading right around low 14AFR.
I hope that now I can really start tunning in a meaningfull manner as I should be getting realistic measurments and readings.
It is a great day!!! Thanks for all the help.

 

IIRC, the tan wire is the ECM O2 sensor ground.
you would definitely have problems without it.

 

Right on! "I love it when a plan comes together"

 

You called it on the O2 ground in your previous post. I just got lucky and found the loose wires. I droped the nut for my EGR valve behind the motor and as I was feeling around on top of the trany, I felt the loos wire lug.

I am so stoked that after 1 1/2 years of banging my head it now works and I can get to some meaningfull tuning.

thanks again,
Keith