O2 sensor help...
 

It seems like my o2's aren't getting signal to my computer. I checked the voltages at the fender of the orange wire and I got around .5-.6 vdc at idle. I know it's running rich, I can smell it.
My anderson pms is not picking up any output signal either from the 02's. Although, immediately after shutting it off, the pms read .48 and .42 for the l and r 02's. But nothing while it is running.
this is killing my tuning, my guess is the computer must sense lean because it is going to full rich.
tired of smelling like gas...

Re: O2 sensor help...
 

You would have to check the signals at the ECM connector, if it's a different reading......time to do some wire tracing. Suggest you do a codes scan to get more information. If the .5-.6 vdc (rich condition for the ECM) are not being read, the system will continue to "add fuel" to the mixture, as you already suspect. LUK

Re: O2 sensor help...
 

Joel,
tx for the reply. Do you have a link to the pcm harness schematic? I am trying to find one now online and in my references...

found it, looks like pin 49 ego ground
43 ego l
29 ego r
I'll be looking for a 5.5vdc-ish signal at the computer.
tx

Re: O2 sensor help...
 

Yup....those are the pins. Don't forget to do the scan though. GL

Re: O2 sensor help...
 

don't have an analog meter, so looks like I'll have to fix the check engine light or find a analog meter...
damn, always something...

Re: O2 sensor help...
 

You don't have to fix your CEL....use a 12v test light or LED. Check the next diagram on how to set it up.
http://www.allfordmustangs.com/techa...s/codetest.gif

GL

Re: O2 sensor help...
 

Remember, don't try to ohm out the O2 sensors themselves or you'll damage them. You should check the wiring between the sensors and the PCM though since they'll often get oil soaked and start to break down. Don't trust your smell along, get a wide band to see what's really whats happening. Are you sure that its not the MAF function that is too far off? The PCM will only correct 25% in either direction so if your maf function is off farther than that, the computer still won't be able to pull enough fuel to get to the commanded lambda.

Re: O2 sensor help...
 

I'm still getting used to the anderson pms, but there are no fault codes indicating a MAF problem from the pms.
Unfortunately, the only sensor the pms doesn't throw a code for is the 02's, but it's obvious signal isn't getting to the ecm.
Thanks Jeff for the ohm check info, I was actually going to do that so you saved me from making a stupid mistake.
I'm trying to pull codes right now, but it's freakin cold out. I'm still trying to use my DMM (it has a nice digital bar graph on the bottom so it's kinda like the analog one)...
It looks like the o2 voltage is making it at least to the fender connector, so right now the problem looks to be between the connector and the pcm.
What makes this more interesting is that I have a MAF conversion harness b/c my car was speed density on top of the pms harness. I've got freaking wires everywhere. :eek:

Re: O2 sensor help...
 

Here are the KOEO codes:
81
82
85
95

the first three seem to be thermactor related, that's been off the car for years.
but the last one is fuel pump circuit related. that one has me worried. I have replace the fp relay and the fuel pump already just a couple of days ago. any ideas?

still working on the 02's...car won't idle for crap right now. runs like ignition timing is all jacked up...

Re: O2 sensor help...
 

If you have the wiring mess you describe, it could also be causing code 95. Once you make it to the ECM connector, check that you get 12vdc at pin 8 during FP priming and engine running. I don't see any O2 related codes but, it doesn't hurt to make sure the signal is getting to the ECM. A Key On Engine Running self-test will also provide good information. LUK

Re: O2 sensor help...
 

touchdown!
KOER CODES
41 EGO voltage always lean, does not switch
33 egr (long gone too, with thermactor, no worries)
91 EGO always lean

now, I'm going to check the voltages at the ecm at the pins
49 gnd
43 and 29

thanks Joel, I will also check pin 8 for 12 vdc...

Re: O2 sensor help...
 

the problem definitely seems to be around that harness connector in front of the passenger strut tower.

I checked the dark blue/green signal wire for the left EGO before the connector and it was around .5 vdc at idle, after the connector, barely anything .04 vdc-ish. I noticed while fumbling the wires around that I got a temporary signal to the pms for the left ego, and then it slowly discharged.
I don't know much about these connectors, and didn't think they could crap out like this. I am now going to cut the signal wire for the left ego and make a new bullet connector for it to test it out.

it would be nice if this is it... :D

Re: O2 sensor help...
 

I can't bypass that connector.
I wired the corresponding signal wires from both 02's directly to their corresponding wires past the connector on the strut tower.
That isn't working. I get voltage right at the newly severed wire ends showing how bloody rich I'm running, but for some reason, that doesn't translate directly to a signal to the computer.
Does the connector do something else, besides the obvious?
Yes, I know nothing about electricity.

Re: O2 sensor help...
 

Nope....it simply "connects", no resistors, diodes, capacitors...nothing. To clear one doubt,...are you checking the O2 signals right at the ECM connector wires? .....did you pierce the O2 wires as near as possible to the ECM connector? (sorry, two doubts). LUK

Re: O2 sensor help...
 

Okay,
now i just checked the o2 signal from each sensor by taking a reading from the pierced upper left white wire on each sensor harness while the car was running and at operating temp.
Only got .4 volts ish on the left and 1.4 vdc on the right.

they are only three wire 02's, so I'm interpolating the chart.

Going to do the key off test now, I'm going to be p-od if I ruined these 02's already.

Re: O2 sensor help...
 

got no voltage on the upper left,
got .67 vdc on the black and got an intermittent 12vdc on the upper right...

sound right? sounds like the 02 is bad...good power, just no signal.

Re: O2 sensor help...
 

replaced 'em again. no change...checking for voltage at pcm
I used bosch 02's from advance auto parts.
going to do a continuity check too from the sensors to the harness...

Re: O2 sensor help...
 

If this is your key on engine off results, the .67vdc(rich) shouldn't be there.

The 12vdc is in the O2's for heating purposes only, not for signal voltage generation. They react to the presence (or absence) of oxygen in the stream and generate the voltage signal. If engine is off and after a short period of time, the signal voltage from the O2's should be very close to 0.0vdc=very lean=no exhaust fumes.
Check this tech article on its description. Even though it's Audi related, it is a very good description of the O2 sensor.

I think your problem is more a wiring issue first, and a possible set of bad O2's second. Once you get the wiring problem squared and replace the O2's, check them out in a KOER self-test. LUK/GL

Re: O2 sensor help...
 

The O2s should toggle about .42, with greater than .42 being rich, less than .42 lean. What you really need is a break-out box if you can manage to find and borrow one. That'll let you measure the voltage at the PCM harness. At any rate, I'd still have to question what makes you think the problem is in the O2s and not elsewhere. The car may be running rich because of other issues, like the MAF transfer function being off. I'd really recommend seeking a good shop that has the tools to see where the problem is. Ask if they have a datalogger (like SnEEC) for the EEC-IV and a wide band.

BTW: It is possible for an excessively rich condition to register as lean with the O2's and vice versa. Also be wary of exhaust leaks. The smallest of exhaust leaks can wreak havoc with the O2s and have you chasing your tail thinking there's an electrical problem.

Re: O2 sensor help...
 

Thanks, Jeff and Joel.
It is running well now, the strut tower connector was a problem and replacing the 02's too seems to have solved the issue.
Unfortunately, I had to crank my regulator up to 49psi at idle (vacuum off) to get the desired readings.
KOER tests show the 02 faults cleared. I did it three times and it drives very well. The Anderson PMS shows the 02 readings flip-flopping back and forth btwn lean and rich. Throttle response is excellent and more importantly, the strong smell of gas at idle is completely gone.
The theory that the car was running lean, so the computer was dumping as much fuel as it could seems correct.
It definitely is running strong, but now I'm wondering if I have another underlying problem in the regulator or injectors.
49psi seems like too much for 24's even with a 76mm MAF/70mm tb, tw heads, etc...
cheers...time for a beer.
I'm taking it the dyno this week for final tuning with a wideband 02.
Might reveal the regulator or injector issue.