240sx Oil Problem

[mazdajoe]

I have a '90 240sx and sometimes it will have loud valve train noise despite having plenty of oil. Now recently I started the car in single digit weather and the timing chain made the rattle like it always does with it starts up except this time it rattled for about 5 minutes while driving but then stopped and it started making the valve noise again. Then I go into target because I think that maybe it is low on oil. I come back outside and start the car and it makes the valve noise again as well as the chain slap noise. I drive it for a couple minutes and ALL noise go away and it sounds to be running fine. Then I drive my girl to go out to eat and it runs fine the whole time (about 30 minutes of driving both ways). Then I go into my girls house and after about 5 hours I come out to drive home. Well it makes the valve noise and the chain rattle the whole way home and about half way home the oil light goes on. I drove it about 5 minutes with the light on and coasted home as to not put too much stress on the motor. So what is the cars problem? Why would it only make that noise sometimes and other times it does not. I am thinking either its a bad oil pump or the oil pickup is clogged. My brother ran sea foam through it several months ago, could carbon be built up in the pickup now? Or could pieces of the timing chain guide be stuck in the pickup? When it did run it also only got 11mpg average freeway and city driving and seems to be running very rich, I dont know what is causing that problem either. Any help would be great , thanks.

[onosqv]

I'm guessing since your timing chain has always rattled, that now it's finally starting to give out?

If it's a bad pump/pickup, you might see the oil pressure light stay on for a little while when you start the car.

Also, since you are in single digit weather, what oil weight are you running?

oil weight info

[mazdajoe]

10w30 im using, of course it hasnt been changed in a while so its probably pretty thick.

[navysnail]

change your oil first before you drive that car any more. go to the store and pick up an oil pressure gauge, they are cheap and will tell you exactly what kind of pressure you have. the gauge goes inplace of your stock pressure switch, very easy to install temporarily. also, when you take the old oil filter off, you may consider cutting it open and unfolding the filter media. it will tell you what kind of problems you may be looking at (keep an eye out for carbon, pieces of plastic, and pieces of metal.