Put a new AC Delco O2 sensor in my 95 Z28, thinking the old one was bad. The sensors starts out reading .450, like it should. As it warms up it goes down to .220 to .250 and stays there. The sensor on the other side jumps around like it should. Does anybody have any idea what could cause this? Thank you in advance.

 

That side of the engine ould be running very lean. What problem are you trying to solve by changing the O2 sensor?

Try swapping the two sensors and see if the problem follows the sensor or stays on the same side, or follows the sensor.

 

The car is running very rich and stumbles on slow take off. I pulled the fpr hose off and it smelled like gas but appears dry. The blm on the other side of the motor is reading 160. This thing has me pulling the rest of my hair out. Could a bad fpr cause this problem? Haven't checked the pressure, don't have a gauge, should I check that?

 

New thing: I reset the computer and at start up it would pop out the exhaust once in awhile. It would also pop when reved. The left O2 was reading low 200's when warmed and the right would read low 900's at the same time. Could it be bad fuel regulator leaking into intake or would that not cause this?

 

If the O2 sensor is ERRONEOUSLY indicating a lean conditon (200mV), the PCM will react by adding an excessive amount of fuel the engine doesn't read, causing it to run rich. That's called a "false lean" condition. Its not due to a leaking fuel pressure regulator (which you could easilly check by looking at the vacuum compensation line - it will be wet. Or try and pull a vacuum on the FPR). That would cause a rich condition on the passenger side, which would cause high O2 sensor mV's and the PCM to try and cut fuel on the passenger side by pulling down the long term fuel corrections.

Swap the left and right O2 sensors. If the problem follows the sensor, its a sensor problem. If the problem stays on the same side, its a wiring problem (short to ground?), or something putting excess air into the exhaust - manifold gasket leak, excessive misfires, leaking AIR check valve, etc.

 

Did you try switching the O2 like Fred suggested?

Did you pull the line with the fuel pump running or after shutdown?

Checking your fuel pressure will never hurt.

Also, you need to discern between "left and right." Use "driver side" or "passenger side" so we know which way you're talking.

EDIT: Fred tree'd me!

 

I checked the vacuum line after shutdown. I am going to pull the injectors and change the o-rings, never put the new ones on when installed the intake back on. How can I check the fpr when it's off the car? This stuff is new to me, my old toy just had a carb, dist, and an alternator.

 

You need to check the FPR vacuum line with the pump running. If the pump isn't running there's no pressure on the rubber diaphram to show whether or not it's leaking.

Are you saying you had the fuel injectors installed without the o-rings? If so you'd be running with a massive vacuum leak.

 

No, there are o-rings but they are the same ones that were on it when I pulled them. I have a new set I will put on to see if it is any better.

 

Ivpulled the vacuum hose off fpr while car was running and there was no fuel there, can smell gas fumes in line. It did change the idle a little with the line off. Took it for a ride again and stool the same , stumbles if you take off easy but better if you get on it. Going to unhook the drivers O2 sensor later and see how it runs, and the reading I get.

 

By pulling the vacuum line off, you increase the fuel pressure by about 8psi. That's going to affect the way it runs briefly. And, unless you held your finger over the vacuum source for the FPR, you created a vacuum leak, which also upsets things.

 

I checked all the injectors, all at 12ohms, power to all pink wires, and noid lights lit up, but one didn't come on right away, may recheck that. Next I am going to disconnect the drivers oxygen sensor to see what it reads. I am wondering if the computer has been reprogramed for mods, which the car doesn't have. The kid I bought the car from bought a computer from a junk yard I think, so who knows.

 

Did you switch the O2 sensors side-to-side yet?

 

Not yet, will try that in a day or two, have family in town and not much time.