Ok thanks a lot for your help. Just let me know what else you need to know or what I need to do next to get this diagnosed.

 

Couple problems:


MAP is showing 11.6 psi. Unless you have a turbocharger or supercharger, that is maxed out producing boost right now, there's a problem MAP should NEVER show positive pressure at idle. Now, it's probably a software glitch, because it should be showing vacuum in inches of mercury, (Hg). Don't worry about it for now.


Ignition timing is showing ~11 degrees. At idle it should be ~18 degrees, but under the circumstances, the PCM may be retarding it for some reason. Timing is not adjustable, just telling you what I see Don't worry about it for now.


B1S2 oxygen sensor, located just in front of the converter, is showing .390 volts, which is lean. That's a problem because all of the other sensors are showing rich. If there is an exhaust leak in front of the sensor, that will cause it to show lean, BUT, B1S3 is showing rich, behind the converter.

 

yea the sensor after the cat is actually only getting like half the exhaust flow. I have cut the pipe just right in front of the cat and moved the cat away a few inches. so some exhaust is getting fed through the cat still.


there are no other exhaust leaks but where I cut it at. so the sensor just before the cat should be reading rich I would assume like both the 2 front sensors.


so if its reading lean then why is the computer still taking away fuel? also I reviewed the live data video again and it shoes bank 1 sensor 3 as lean. about .120 or so. which makes sense since the pipe has been cut.


also its really hard to start up when cold, first start. I usually have to put the gas pedal to the floor for it to start. I keep it held till the rpms come up to 2 grand then I let off a bit. I have to keep tapping the gas until it warms up a bit for it to stay running.


what do you think I should do? thanks

 

maby I will swap b1s1 with b1s2 and see if it changes to b1s1 being lean. then we know we have a bad sensor right?

 

We pretty much know B1S2 is wonky. B1S1 and B2S1 are both seeing a rich mixture, and there's nothing downstream of them that can change the mixture before it gets to B1S2.

 

So what do you suggest i do.

 

In your situation, with both upstream sensors showing rich, B1S2 must also show rich, and it's not. Replace B1S2.

1995, (CMFI) had one fuel injector that was "batch fired" for all cylinders simultaneously, (only one bank) so it didn't need sensors in positions B1S1 and B2S1. It only needed sensors in positions B1S2 and B1S3. 1996 and newer, (CSFI) fires 6 injectors individually, in two separate banks, so it needs B1S1 and B2S1 to control the fuel mixture. B1S3 position, on both systems, monitors the efficiency of the converter, and it does not affect engine performance at all.


1996 & 1997 were the only years that used B1S2. In theory it should indicate an average of B1S1 and B2S1, but with CSFI, the data is already split into two separate banks, why merge the data???? GM finally realized the data stream was worthless, and eliminated the sensor starting in 1998.

 

ok I got the new sensor installed. bank1 sensor 2 and it still runs as bad as it did before.
it seems when its really cold out "15f" its harder to get started. it wants to backfire out the exhaust sometimes.

 

Bring it up to operating temp, and hold at 2K rpm. Another video, just like the last one, would be great.

 

ok will do