Replacing oil pressure sensor during an oil change, gauge still acts funny

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10,957
Location
USA
I changed the oil on a 2001 Firebird V6 and replaced the oil pressure sensor along with it because you have to drain the oil to replace it anyway. The oil sensor didn't work right and was lazy. It is a very common problem on these cars. The old one still had some of the threads showing because it uses a tapered thread, which is weird, but whatever. When I installed the new sensor, it shows the same amount of threads as the old one did, and it was clocked in the same position as the old one. The new sensor is ACDelco GM Original Equipment.

The new sensor is obviously behaving better then the old one, but it still doesn't seem to be as smooth as it should be. The gauge will show the pressure around the middle (60 psi in this car), a short delay, then the reading will go up when you hit the gas, but it jerks right to the higher reading rather than a smooth movement of the needle. When you take your foot off the gas and it idles again, the needle will go right back to the middle, again a sudden jerk movement, not a smooth slide back.

Upon shutting the car off, the gauge needle goes to a quarter (which would mean 30 psi); it's supposed to be zero when the car is shut off. If you wait a few seconds, then turn the car on (but not starting it, so KOEO) then turn it off again, it will go to zero. This is the case before and after replacing the sensor.

Does the new sensor need time to relearn? Does changing the oil have any effect on the needle's reading when a new sensor is installed? Is the problem something else? I heard the oil level sensor could be bad, but the low oil light isn't on (the usual sign of oil level sensor failure is when it says low oil but plenty of oil on the dipstick)
 
Messages
113
Location
VA
Especially in GM trucks, I have an '04 Sierra and the speedometer stopped working right after the warranty expired, GM would've still honored the warranty as I was only a few thousand miles past but they would've repaired just the gauge that wasn't working so I shipped the cluster to be repaired by someone else who then replaced all the stepper motors and not just the one that failed. I don't remember the years exactly but my friend had an '05 and his was not included in the recall.
 
Messages
1,967
Location
USA
Look at Cline's post above ( that was what I was thinking when I first read your situation assuming it was strictly analog but not sure)

If that's the case (and I believe it is) then there are basically 4 possible scenarios assuming a sending unit with no hysteresis or calibration ability....

That actually is the pressure its reading ( spikes and all) and the old unit was really screwed so you are normal

The unit is defective (this would take someone capable of instrument calibration or home electronics to put test pressure on the unit and read the values)

The conductor has some degree of short or whatever altering the signal ( would require a jumper to confirm/eliminate this)

The gauge proper has a malfunction ( would require a bench test like the sending unit)

Personally, I feel anything short of the 4 above is just guessing
 
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