Since I hooked my car to the diagnostic program, Craig Moates Software, I have noticed that I ALWAYS get a reading of 4 in the O2 category. Also, I burn through fuel like crazy eventhough my datalogs all show the BLM's climbing to 160/196/1xx whatever instantaneously when I let off the gas or at a stoplight.

Is this a sign of a bad O2 sensor?

 

Yeah mabye, no voltage o/p form the sensor, so the ecm would think there was no excess air, so it would try to lean the motor out (eg. blms going below 128). but your going pig rich, so maybe you cracked the porceline on the o2 sensor, this will make a rich condition. I think I got this out right.

 

Yeah, I just pulled the O2 sensor and it was black as 20,000 mile old motor oil. I cleaned it with gasoline. Then I started the car and brought it up to a stumbling 4000 RPM and cut the ignition. The plugs are also black as sin. I am really getting PO'd at all the little mechanical things that go wrong that makes modifying the .bin so friggin nerve racking!

Oh well, back to the grind-stone :rockon:

 

I wrote this to you in the other post. So no, just because you are getting 4 mv from the o2 it doesn't mean you have a bad o2. You need to do some checking.

 

For what its worth, you should just replace the O2 sensor, then wire it up nice. That will eliminate some problem possibilitys.

 

hectorsn, I have a question about the exhaust leaks. I am pretty certain that I don't have any leaks at the headers where they mate to the heads because I simply cannot get the bolts any tighter. On the other hand (BTW...I am using the SLP headers and their 2-piece Y-pipe) I did not weld the break in the Y-pipe where the 2 pieces slide into eachother. This break is after the O2 sensor. Is an exhaust leak after the O2 sensor going to cause this or are we solely speaking about an exhaust leak at the Heads/Header junction?

Maybe I'll see if we have any starting fluid and check for vacuum leaks at the intake. Headaches!!! I feel one coming on lol.

Thanks guys!

 

If it isn't that far back from the o2, yes it can make a difference. But to peg the o2 at 4 mv all the time I would *guess* the leak would have to be bigger. I am also guessing that the car runs fairly well when in open loop? The reason I say this is because I had to fix a car like this once. THe car ran nice after you changed the plugs as they were fouled bad. Started up and ran good until it hit closed loop. Very noticeable change in the way it ran, even without any diagnostic machine hooked up. When I did hook a scanner to it I immediately saw the o2 at right around 4 mv and the blm climbing quickly to 160. Well I shut the car off and unplugged the o2 with the key on. No difference so I unhooked the ecm connector and checked the o2 circuit for gound. Sure enough, about 5 ohms to ground. Started peeling off the o2 wire by the harness where it goes behind the drivers' side valve cover and found my problem: o2 wire rubbed through to the head by the bellhousing. Fixed the problem in no time and it ran good once it hit closed loop. The o2 probably should have been changed since it had seen so much fuel but it wouldn't have resolved the problem. Like I said, you need to do some checking.

 

Burn an open loop chip, and see how it runs.
Set the C/L enable temp to like 254 (FE)
If the car runs moderately well, but with weird O2 volts try a different O2.
If no difference, then you know something else is to blame.
Then go back to a C/L chip.

 

hector and Grumpy, Thank you so much. I will get on this today. I am gonna try to get all the exhatse leaks worked out today as well as checking the O2 circuit.

I do have 1 question though. I assume there is a certain wire that runs directly from the O2 to the ECM. If there is which plug is it in of the 2 connecting to the ECM and of course, which wire is it? This way, knowing which wire it was, I could check the circuit to see if the wire has been grounded.

I will burn an open loop chip also in about 20 minutes. Thanks!!!

 

http://www.diy-efi.org/gmecm/ecm_info/1227165/

 

Ok the open loop chip makes the car run like a champ! There is a little bit of an irregularity here though, and therein lies the problem.

Before I burned this chip, I had the ARAP.bin as mu base. When I started the car, and subsequently drove down the road, it would lean out very fast and begin to bounce back and fourth as if it were starving for fuel, and it essentially was. This was all in OPEN loop. It would hit closed look and then become more violent until it hit an SES code induced open loop where it would smooth out but the problem would not cease to exist totally. it was still apparent.

This new chip I burned, remembering that ALL I changed was the Fan turn on temps and the Open loop enable to about 110* C, runs as if the car had never gotten a built motor. The bounce was completely gone at cruise and at idle. It never tried to stall. It was as if the chip's open loop setting had everything to do with the problem. I don't understand it. But I like it, for now. Thanks for the temporary fix guys, now on to the big possibilities.

 

hectorsn, I assume that the link was for the bua hack at the bottom of the page. I took a look at it and from a purely logical standpoint it makes sense. But since I have no idea what all the computer language means its quite a task for me to understand. I really struggled for a while trying to figure out what I was looking at sometimes.

On another note. The Open loop chip I burned seems to rule out vacuum leaks. How? Well a vacuum leak would prompt the ECM to pull in a little bit more air because of the loss of pressure right? With the Open loop chip the RPM's stay steady at idle. Unfortunately I angered the guy whose cable I use for the diagnostics and I am kinda afraid to ask to use it again. Oh well We'll see about it tomorrow. So as of right now I only have my seat of the pants feelings when trying to diagnose the car. My head tells me though that the Intake is ok, no leaks anywhere, no surging anymore. So there are only 3 things left to be the culprit. #1 My O2 sensor has given up the ghost. #2 I have an exhaust leak. or #3 ( I read this in a post over on camaroz28.com) I am having a lean misfire which would cause a rich exhaust signal in the O2(and also a rich exhaust smell) and prompt the ECM to cut fuel when in fact its truely lean and that would be why black smoke would shoot out of the tail pipes at idle.

Does my train of thought seem to be on the right track here? Or is it about to derail and cause a Firey explosion?

Later fellas, as always you are a big help and more appreciated than you know.

 

Ok guys, Its been a while but I was able to convince the guy to let me use his cable again. I built another cable this week that didn't work either... Anyway, the O2 sensor voltage NEVER moves from 4. Soooo Should I go to a heated O2? I have checked for any breaks in the wires, but found that the wires are not exposed anywhere and are completely encased in the Wire looms until it reached the O2 sensor.

So Heated O2 on the SLP shorty's or new 1 wire O2?

 

Did you check the voltage with the o2 wire off? It should read around 450 mv with the o2 disconnected. Did it? The reason I gave you that link was so you could see the wiring diagram. It's way at the bottom of the page.

 

I'll go check that out in a minute. I assume you mean with the car running?