Some background
stock cube lt1 with cc306 and 1.6 rockers. mail order tune.

5k on msd wires
5k on msd coil wire
5k on new gm opti
3k on new coil
5k on bosch o2's
3k on new spark plugs
pcm was reprogrammed 5k ago also
gas is premium, with some lucas fuel treatment

i ran the car for 2 weeks with the o2's unplugged and it ran like a champ. I got the cable to log my car via datamaster and hooked the o2's back up and the problem came back. I have the logs but i'm not sure what they tell me. Another note is that their are several codes in the log, but the o2 codes are there because i've been driving it without the o2's.


anyone out there got time to take a look? i can email the logs. Thanks in advance!

 

Who did the mail order tune? If it was madz28... I had same problem. And the problem is actualy in the tune, and it makes the o2's go wack.

 

yes it was him, but my car was fine for 8 months with the tune then started messing up.

 

Do you have aftermarket headers and if so when where they put on and where they coated?

 

i do have pacesetter coated longtubes, they have been on since last year in springfield, mo. I have done nothing to the car since all of the motor work was done a year ago. Nothing has been changed in the car, it ran fine for 10 months. Then started messing up, nothing was changed.

 

Mine ran fine for a while too. But the o2's kept giving out after a while. Had a local tuner that is very reputable look at the tune on my computer, he found all sorts of stuff wrong. He doesnt even want to start off where madz28 left off, he wants to just redue the whole thing.

 

Pacesetter coated headers are the worst for ruining O2's but i would think it would do it faster than the time frame you are talking about. If you had a rich issue that could have caused them to go out or they were damaged but barely able to work and over time finally bit the dust.

 

is there a way to test the o2's to make sure?

 

The way to test them is check your datalog if they don't change rapidly from the 1xx-8xx and show 800-999 during wot runs its time to change them. Just don't make the mistake and buy an off brand and go with the AC Delco and maybe get 80,000 miles or more out of them. My 100K set still appear to be fine but i replaced after the headers install.

 

Have you tested the O2 wiring for shorts or opens?

 

Don't know how. Would i just check the voltage of the harness while the car is running? Harness as in where it plugs in to the o2.

 

This is out of Injuneers writeup. http://members.aol.com/InjuneerZZ/ScanMast.htm

"A word of caution here - I hear a lot of people asking if they can just measure their O2 sensor voltages with a voltmeter. Everything I have read says the answer to this is probably "NO". First, the O2 sensor generates a small current. Many VOM's also apply a tiny current to the circuit. This current can damage the O2 sensors. The caution in the Howell Engine Development Manual states:

"If measuring sensor voltage with a voltmeter, make sure the impedance of the meter is at least 50megohms. And, the resulting voltage measurements can still be off by 200 - 300 mV's. "

I have never tried to use a voltmeter on an O2 sensor, so I don’t know how well it would work, but based on the above, it sounds risky."

 

so that is not an option, what is the best way of testing it then? I know it seems frugal, but i don't want to spend the money on 02's if i don't have to, i just want to make sure thats what the problem is if there is a way of doing so.

I just watched my log again and one is always 150ish higher than the other. At wot one sits around 850 and the other around 950. They should be close to around the same correct?

 

Yes, within maybe 20mV of each other.

e-mail me the log. Can not be a .zip file. Show your screen name and the words "data log" in the topic. Not sure when I can get to look at it, but I'll try.

 

you should also take a good look at the wires that go to the o2's and make sure they did not get melted or something