Questions and Answers
Firebird Oil Pressure
Q. Hey Vincent, great column. I searched the site for the same problems I'm having, but I haven't had any luck, I hope you can help me.
Car Specs:
1991 Pontiac Firebird
3.1L V6
Auto
105,000
Fuel Injection
No ABS
A/C and CruiseAnyway, here are my dilemmas...
1. My heater (blower) in general. It's spotty. It works sometimes, and sometimes it doesn't. Normally, it WON'T work when I start the car, but works after a little time on the road (usually when I hit a bump). Seems like a short either in the switch or somewhere in the wiring to me, but I'd like your opinion.2. Oil Pressure
This problem is a bit more serious, as it deals with my oil pressure. Ever since I bought the car (about 10,000 miles ago) the oil pressure had remained a consistent 66psi under normal driving conditions. A few weeks ago, I noticed a drop from 66psi to 40psi suddenly. I had the car checked for oil leaks, and found none. I had the oil filter and PCP valve replaced, with little-to-no effect on the psi (according to the gauge). The gauge still works normally, it's just reading everything 20psi lower now. The car is running fine (it seems). I'm curious if this is a bad gauge or a bad pump. Please help, I really don't want to blow up my engine!
Thanks,
DanielA. The problem with the heater sounds like a bad blower motor. When the brushes in the motor start wearing out, it will do the same exact thing. What you can do to confirm this is to use a test light to see if the motor is getting power when the symptoms appear. If there's power, then you have a problem with the motor. If there is no power, then I would think it is the switch or wiring.
As far as the oil pressure goes, the only way to find out for sure is to do a mechanical oil pressure test. The Oil Pressure Switch (OPS) is removed and a mechanical gauge is put in and it will tell you what the actual oil pressure is. You can compare it to the gauge reading to check for gauge accuracy. If it is off, then install a new OPS and you'll be okay. If the mechanical pressure test does indeed show low oil pressure, then you need to look at the oil pump.
The spec is 38 psi@2000 rpm so 40 psi is okay. The 66 psi seems like it's too high.
