if you are getting a stumbling feeling from engine, missing bucking, check Both oil sending units, My 2000 drove me crazy till i found the rear 1 leaking, in my case the problem just got worse until i found it.

 

Drove the car to get coffee today. Drove it over 3 miles and while sitting waiting in the drive thru it started missing. This time it go so bad that after 30 seconds the car actually died. This is the first time the car has actually died. I turned the key, car started back up and ran fine. I drove home and let it sit running in front of the house for 20 min. Ran smooth and never missed once.

I even had the OBD2 tool reading real time data this time when it stalled an I didn't see any problem with the MAF voltage the O2 sensor or anything else.

I'm really stumped. I don't want to take it to the dealership cause I know it will be just like when I'm sick and make a doctors app and then the day of the app I feel fine. I'm sure the car will run just fine if I take it to the dealer.

 

Are you referring to the pressure sending unit that goes to the pressure gauge? I'm not sure why the car would have 2.

Was yours leaking so bad that you lost oil pressure?

This car for sure is driving me crazy.

 

Can your ODBII program tell you which cylinders are missing or any of the misfire data?

 

there are 2 pressure units, 1 to computer 1 to gauge, my gauge worked fine, the 1 for the computer was the problem, it just slowly got worse, till it stranded me.

 

The OBD2 computer is not detecting any mis fire. When I pull the fault codes it reports that it found none. Make sense because the check engine light is never on.

So if the pressure sending unit to the computer goes bad that causes something that feels like a misfire and will stall the car? I'll replace it if it will help. Any way to check it? Where is it located?

 

In the past I have experienced misfire do to:
+Bad coil. Threw a code for misfire (replaced all coil packs)
+Leaking fuel pressure regulator. Threw a code for misfire (cause was no fuel to engine. Replaced easily as the fuel pressure regulator sits right out in the open at one end of the fuel rail)

 

I only wish mine would throw a code or the problem would happen in front of my house while I have it sitting there running for 20 min so I could trouble shoot it.

 

I confirmed in the GM shop book, the 3800 and 3400 v6 engines only have 1 oil pressure unit.
The 3400's use a switch (it's on/off), the 3800 uses a pressure sensor (reports how much pressure, not just on/off). Both drive trains connect the oil pressure unit to the same pin on the PCM. The clusters for these cars get all gauge readouts (and more) from the PCM directly on a data wire (only a few things like turn signals come elsewhere to the cluster). GM has not ran individual wires for sensors to the clusters in a long time.

Some people have mistaken the Knock Sensor for an oil pressure sensor. If the knock sensor is malfunctioning then it stands to reason the car might do a lot of unusual things based on bad readings from that and attempts to correct it the performance based on those readings.

Unless it was a part that makes sense to replace for good maintenance, I'd hate to have recommend you shotgunning parts to see what works.
I know my old '94 Grand Am (which used the same coils our Montes used), had a misfire that was a pain to find. And that is I believe ODB-I and did not record misfire data like modern cars do. Using a scan tool I found when it malfunctioned, the Injector Pulse Width (how long the injector was open), became a larger value then when it ran properly. In the case of that car, I found the problem by accident, a failing coil. I found it by how I rested my hand on the top of the housing, I could make the problem come and go (at that point, I had swapped ICMs with a donor car, so the coils had been reseated already) and no changes. I swapped the one faulty coil and all better, no more random mis-firing.
Sadly, I don't think this gains us traction on your current problem, since the computer is not reporting a mis-fire. Even though your not seeing any mis-fire codes, the computer still keeps a record of each cylinder and how many mis-fires it's detected since codes were last cleared. Can you access that data at all? It may give us some clues.
Can your scan program show "pending codes"? These are internal diagnostics that have failed but have not met the failure frequency to actually display a light on the dash.

Outside of that, I am not really sure what train of thought to do next to diagnose this issue

 

when i had the missfire and eventualy got worse, acted like it was out of gas, would not rev higher than 4000 rpm. My mechanic has the big *** computer we put it on drove it around no codes, started missing died no code. He said he traced back by wiring diagrams to a oil pressure switch. He is out of business,so i cant go check back to ask him. wrecked his Harley in Tenn. on the dragon. He is real bad in a nursing home for good.