Oh my, I do not need this now. Here is the story:

We are getting ready for a very large, high class car show this coming Sat. and we have been cleaning the 95Z for about 2 weeks now, just getting it ready, and to have plenty of time. I have always cleaned well, but this time, I went further. I removed
everything I could from the engine bay to wash it down really well. This is what was removed:
K&N CAI, MAF, rad. cover, bellows, Optima, STB, we unbolted the PCM from the body of the car, but did NOT unplug it. All we did was move it away from the area it sets in, very carefully, just to clean in there, and it was wrapped up very well. I just wanted to wash all the **** offthe engine bay. It wasn't really dirty, just never been washed before. We also covered the Opti very well w/ plastic and made sure it was out of harms way.

We cleaned, and put everything back together. I started it up, and it started just fine, sounded great at first. I have a Scanmaster, and instead of it having the fluctuating 3 numbers it has on the main screen, it had 999 0.0 retard. It should be like 450+ in open loop. I scrolled through it, and everything read fine, even the BLMs at 128, where everything was reset. But the right O2 (pass. side) was reading 999, while the left 02 was reading the normal 450+ in open loop. I also noticed the IAC was like 152, it was weird.

My air/fuel gauge was ALL THE WAY to the TOP at rich in RED. I have never seen it past normal before.

We went through and checked all the grounds w/ a meter, they were fine. I looked and looked, and I couldn't see anything unplugged. I was NO where around the 02s, I don't know what could be unplugged to make it read 999, or MAX rich and not even registering.

If some of you could point me to the right direction, I would be HIGHLY in your debt. This show coming up, I have been anticipating it for 4 months now, and cleaned this car to the max. It would kill me to not be able to go b/c of something as stupid as this.

Sorry this is so long, but I would love to hear some good suggestions from all of you.....

Shoebox, where are you? lol

BTW, we cleaned a few parts with very fine steel wool. This included the MSD box, those lines on top of it. That shouldn't hurt it, should it? I just didn't know if steel wool would affect anything.

HELP!

 

your O2 is probably either dead or dying... same crap has happened to me. Does the sensor work once it warms up b/c mine did eventually but I still replaced it as the O2 wasnt accurate at all. If it was unplugged then it would show 450mV.

 

What happens when you swap O2 sensors right and left?

Ryan

 

Well, I didn't switch them out, since this was just a test start after the cleaning and painting.

They aren't that old, maybe 1-2 years, and less than 5-7k miles on them. The car has Longtubes. The last time I had a bad 02, I got a code, and the readings were different. On a scanmaster, max rich is 108 and max lean is 160. This was a 999 which is like it is not receiving a reading at all. That is what freaks me out. I looked over it, and couldn't see why it was doing that.

And the air/fuel guage, that usually fluctuates at idle, was TO THE TOP in red, RICH. And wouldn't move. Almost like a vacuum leak
or something strange.

Keep em' coming guys!

Thanks!

 

I believe if you unplug an O2 sensor the scanner will read 450mV.. not 999mV but i could be wrong. 999mV is the sensor demanding more fuel so that would explain why your AFR guage is showing rich.

 

Right, I see your point, which is why I don't think the 02 is necessarily bad. But this car was in excellent condition before we did any kind of cleaning. Could something be unplugged that I am NOT seeing? What could be unplugged on the pass. side that would have to do w/ the fuel that is affecting that one 02? I don't think it could go bad just by sitting on jackstands for two weeks, lol

It was working perfect and NO fuel problems whatsoever.

Thanks for that idea, I didn't think about the demanding more fuel.

 

A friend of mine also suggested that it could be a power short to the 02 itself? A chaffed wire or something?

But I don't see how it could be working perfect for so long, I decide to clean it up really well, and it happen right after I got it back together??????

What could have happened during all that, to cause it???????


999 mv reading????

Thanks for all the help so far, please keep em' coming!

 

why dont you try switching the O2s around to see if the problem is in the sensor or the wiring since you did have to install that afr guage.

 

I am sorry if I confused you. I have had that guage installed, along w/ my Scanmaster for over 2 years now

I have had bad 02s before, but never got this reading. It was always a 108 max rich or 160 max lean on the Scanmaster. And it had codes. This doesn't have codes. I am really confused.

Thanks, and keep on!

 

Since the only thing you did related to the O2 sensors was pull the PCM out, is it possible you either got some water in one of the connectors, causing stray voltage to leak into the purple O2 sensor signal wire, or you broke the insulation on the wire and are getting voltage leaking from on of the +5V reference sources in the connector.

Swapping the sensors left-to-right is the foolproof way to track down the problem... if it stays on the right, its the wiring.

Both the A/F gauge and the PCM/ScanMaster are responding to an excess voltage in the circuit. You need to track down the source.

 

That is the only thing I can think of that I did that could affect the 02. It was just some cleaning, and I wanted to clean behind the PCM area. So, we pulled it up, and pulled it easily, over towards the driver's side. It seemed to go over pretty easy. It wouldn't be in any grounds or fuses or anything I am not seeing, would it?It is just weird how the pass. 02 is acting up, and knowing the PCM is on the pass. side.

I will swap the 02's today. Can a bad 02 show a reading of 999 though? I thought it would show 450 and not move. Kinda like when the little heaters inside get broken.

Injuneer, have you ever seen that before?

Thanks everyone, I really have to get this fixed within the next 2 days.