Looking for advice

Service Engine Light (SEL) threw code P0107, or, as the internet states..."P0107 is the general code for a problem with the MAP circuit sensor having too low voltage input to the Engine Control Unit (ECU). This means the voltage input to the ECU is . 5 volt or less which means that it is not in the correct lower range for proper engine operation." The car seems to be running just fine.

I haven't pulled off the plastic engine cover to look yet to see if, in the unlikely event that somehow the connector came loose somehow with using an engine hoist...but I'll check. And I'll check this site as well for any tips OR...feel free to chip in.

Causes of the P0107 on the GM 3800 engine might be ---

Bad MAP sensor
Disconnected vacuum line
Open or short in the signal circuit
Open or short in the 5 Volt reference circuit
Ground circuit open or shorted

Solutions might be ----

Test MAP sensor, replace if needed
Check for vacuum leaks
Check plug for corrosion or damage
Test signal circuit wire
Test 5 Volt reference circuit wire
Test ground circuit wire
Ensure harness is not routed too close to high-voltage wires, such as spark plug cables.

My guesses are ---

MAP sensor co-incidentally died - to check this you should use a scan tool and look at the output voltage. If it is responding but running low, replace the MAP. See service manual for the relevant voltage range. I think it will be about like the table at the bottom of the article at this LINK.

busted/bad vacuum line

bad gas (rare)

something got pinched, loosened or disturbed because you hoisted the engine instead of jacking it (just kidding)

Albertj

Yeah, I saw that info on the Internet for the P0107 code.  I pulled the engine cover off and checked to see if a vacuum line had come disconnected.  No such easy luck.  The vacuum lines are made of an inflexible plastic and I had broken one of the "T" connectors when I did the lower intake manifold...specifically the one under the supercharger snout.  Jimmyrigged something up with flex hose and it seems to work, but tomorrow I should be able to get a multimeter on the electrical connectors.  YouTube guy did a video on how to test a MAP sensor (as well as a MAF sensor), and he's a pretty good teacher...Ratchets and Wrenches is his handle.  I reset the code and drove it about 10 miles...no light came on.  However, as soon as I parked, I restarted the engine, and the light came on.  2nd incidence of this happening in this fashion. so I'll test the electrical connectors and spray some starter fluid and see if I can detect any vacuum leak.  With a 21 year old car, it's always something.  At least the belts are working perfectly and the motor shows no signs of falling out.

No kidding I doubt you have a vac leak if you've maintained the system.

Over the time I have owned my Riv I replaced the vacuum harness twice. Once I pulled it and patched one together with COTS parts and the second time I just purchased one from the GM dealer (at the time they were about $20.- ) That one is still in use. What the parts guy did was, when he noticed the SKU for the '98 Riv vac harness was discontinued no replacement, he rolled his eyes and looked it up for the latest Chevy Impala that had the 3800 engine in it -- apparently the gearheads at the dealership had already figured out that the Impala vac harness fit exactly. So for all the late model 3800s, they just use that one. He said, "I don't know why they do that."

I have a peek-a-boo P0107 that comes up when I burn 91 octane gas from convenience stores and goes away when I burn a tank or so of top-tier premium (Exxon, Sams Club, VP Racing, Mobil, Phillips 66, Shell) or mix in fuel (the higher octane the better) that has no ethanol. Started as a solid P0107 when I had a cracked intake manifold, which I fixed. Went away and came back as a peek-a-boo (intermittent). I am not sure why it does it now. Maybe the replacement cracked (it was a used one that I ported he he). I'll know maybe this weekend.

Step 1:  Find out where the MAP sensor is.  Internet provided picture of what I thought was it, and looked a bit harder and noticed it was actually below the thingy above it, on the firewall side of the motor.  Guess the clue should have been that it snugs itself into the manifold.

Step 2:  After looking in the factory service manual for the color codes for the 3 wires, and writing them down, it's off to get the multimeter.

Step 3:  Wiggle off the wiring harness hooter.  Oh wait...the wiring harness hooter is ALREADY DISCONNECTED.  D'oh.  Look to see the little flange that supposed to hold the hooter in place was broken or perhaps got knocked off when I hoisted the motor while changing the belts.

Step 4:  Reconnect hooter, zip tie hooter in place, clear codes, start car...no code.  Then turn off motor and restart car.  Service engine light remains off.  Pretty confident P0107 is history.  Hopefully end of story.  Felt so good about fixing that problem, I replaced the little flippy vanes in the HVAC system where you can direct the air flow.

Step 5:  Decided to dash off for an exciting round of polo with Ralph Lauren and Prince Charles.  I may offer them a ride.

Glad you found it, Christen.

"something got pinched, loosened or disturbed because you hoisted the engine instead of jacking it (just kidding)"

Albertj

I would like to know what a wiring harness "Hooter" is.?????

Glad you found the problem and had a day with the Royals.