Oil light at idle when warm. Common in Cavalier & Sunfire

[doug2060]

Hello, More than a year ago I bought a 1997 Pontiac Sunfire 2.2 CHEAP. The only problem with it was that once it got to operating temperature the oil light would come on at idle. The guy I got it from owned a small used car lot and couldn't sell it because of this issue. He replaced the sending unit, oil pump and pickup tube/screen. He even provided proof of this. He sold me the car for $400.00 with only 80,000 miles. Once the gas pedal is pressed even slightly it goes out. Sometimes it flickers and sometimes it's solid. Over the past year I have researched this problem and found it is VERY common in several year models. I have even found reports of cars with less than 20,000 miles doing this exact same thing. I have partially disassembled my own engine to take measurements etc. All clearances between bearings etc are normal. Recently I purchased an oil pressure test kit. I was unable to get the pressure to drop below an acceptable range but it would get right on that fine line between OK and bad. Strangely I noticed that while at idle the engines performance fluctuates slightly possibly causing the issue and putting the oil pressure on that fine line between good and bad. I have still not fixed my LIGHT issue but I have a possible lead.

Speaking to an ASE certified mechanic familiar with the issue. He claims to know the cause. Strangely enough he claims the issue has many factors involving mainly the ECU, fuel pump, and fuel filter. He says that it is a problem because all the other things affecting the ECU causes overall performance and efficiency to suffer. His advice: Replace the fuel pump & fuel filter with high performance "high flow" aftermarket units and avoid OEM or equivalent units. According to him this has corrected the problem on 2 different occassions in his shop. In one case it didn't stop the light from flickering on a high milage vehicle and only improved it slightly. He recommended replacing the sending unit entirely with a seperate aftermarket gauge. In all cases the overall vehicle performance was improved including a more stable oil pressure reading.

My question is, does this make sense? I would hate to spend all this money on performance parts just to find I was fed a line of crap. Any opinions or thoughts are much appreciated and I hope other googlers may find this post helpful.

[viggy58]

sounds like a load of crap to me...

i'd take it somewhere else for a second opinion. what are the exact oil pressure readings you're seeing?

[Cadaverlier]

I just put a motor in a '97 Cav for my daughter to use that I got out of a junkyard. It has like 180,000 on it. It does the same thing. I figure it is just old with worn bearings with extra clearance and such. I don't give it a lot of concern. If I was worried about it a lot I would just hook up a mechanical gauge so I could see exactly what it was doing. As long as it's only at a slow idle I wouldn't worry. Back in the day it was a common thing with a lot of Fords that had a lot of miles. I guess the oil pressure units had a pretty high rating to turn them off. Chevys wouldn't turn on until the pressure was almost zero.

[jamesslcx]

First I've heard of this, there may be something to it or not. Anyway I would step up to next thicker weight of oil and see if it helps.

[Cadaverlier]

Certified mechanic with what sounds like a certified line of crap to get you back in to his certified shop to make him some more certified money. Fuel filter and fuel pump make you have low oil pressure??? I wonder if for the two times it helped if he charged for all those things and then just sped the idle up another 100 rpm enough to make the light stay off.

[Cavalier507]

I do think it is possible cuz I build my own cavalier ls and I know that the fuel pump was not working fine because I can hear a buzz coming from it, also it does not have enough power... it can be a posible cause of the issue or I don't know it can be something else. If you were able to fix it please answer me I would really appreciate it.

[Tech II]

The ONLY way a new fuel pump puts that light out, is if it increases the idle of the vehicle.......you can do the same thing by resetting the set screw for the throttle plate.....but that creates other problems, like TPS, hard shifting into gear, etc.

But if you have no starting problems, or accelerating problems, I doubt it.....you should put a gauge on that engine and see what the actual pressure is....I think the idiot light works at 4-5 psi, which is not much in a working engine.....

Most common cause of low pressure is excessive clearances(bearings), especially in older vehicles...

[DeltaP]

No mention of actually checking the idle speed and fuel rail pressure but were gonna replace fuel pumps (?). Ahhh fugetaboutit... this thread is over a year old.

[j cAT]

Originally Posted by Cavalier507

I do think it is possible cuz I build my own cavalier ls and I know that the fuel pump was not working fine because I can hear a buzz coming from it, also it does not have enough power... it can be a posible cause of the issue or I don't know it can be something else. If you were able to fix it please answer me I would really appreciate it.

so you want to increase the idle speed so that the oil pressure light goes out ? I never had anyone ask that question before.

since the oil light is on I would use a 30 wt oil see if the oil light goes out . if it does then you need a new/used engine cause your engine is worn out. this happens when you go too long on oil changes and also run the engine with low oil because it is loosing it..