Lights Dim & Low Oil Pressure

A compression test will help give you an overall state of your engine, but won't tell you much about the wear on the mains, rods and valve seals; besides a worn pump, if you're having low oil pressure issues, worn moving parts is where the pressure loss is most likely to be. If you aren't burning oil, your compression should be okay, The comment of keeping in mind a high flow pump is not necessarily a high pressure pump is a good thought to keep in mind. I know from experience that if your engine has a lot of wear, that oil, like anything else fluid, will choose the path of least resistance. The second thing to remember things that may not leak as a lower pressure, can leak at higher pressure.

bear108 said:

I have a 92 lx 5.0 with a fair amount of motor work done to it. Even before I did motor work n it was all stock, when I come to a stop, head lights dim and oil pressure gauge drops really low. Oil pressure drops at a stop, even with no head lights on, no radio or fan. I have recently replaced alternator and battery with new. I have had this problem for years and would like to try and fix it. Any ideas would be greatly appreciated.

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What is your idle rpm. Do you have AC? If so, does your idle drop only when the AC is on or also when it is off? My '89 did that, idle drop, alt gauge dropped to about 9 volts when I sat at a light with the lights on. It was worse when I had the AC on, it would often stall when I let off the gas while stopping for lights. I also replaced the alternator and battery after the alternator failed the bench test, and the battery the reserve starting amps test, but still had the low idle, stall out issue. Reading comments on the Idle air controller IAC and the throttle position sensor (TPS), I decided to replace them, first the IAC, then if that didn't work, the TPS. Before replacing the IAC, make sure your timing is correct (be sure to take the jumper out when you set the timing, then remember to put it back in!). Then replace the IAC, and but leave it's electrical leads disconnected. Disconnect the negative lead on the battery and turn on everthing you can think of to drain the electrical system of all electricity. I've heard leave it like that all night, but I think that is unnecessary, 20 minutes worked for me. turn everything back off, reconnect the battery and start the engine and adjust the idle screw get the idle to 800 to 900 rpm and let it idle for at least 2 minutes. Turn the engine off, reconnect the IAC, and then start the engine and turn on lights and a/c let it idle a couple of minutes. If this doesn't solve your idle / stall issue, then I would try the TPS next. This solved my idle issue, I haven't had the engine stall for over a year now.

PS I've considered going to the 130 amp alternator, but after correcting the idle issue I don't see the need to do so. If I have to replace the alternator again, I might do so then. There is some rewiring necessary but it's not odious. If I replace the alternator I will also replace the stock starter with one of the mini-high torque starters, again more rewiring but if you can read the instructions, not to hard to do. the last batteries I have bought have all been gel batteries, so far I have been quite pleased with how they perform. My wife drives her CX9 about 4,000 miles a year, the lead/acid batteries had trouble keeping a charge, the gel battery is handling low miles without issues.