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Several problems, Loss of oil pressure after filter and oil change. Random Code P0304
Hello. I'm new to the forum but I have been reading various post for a time now. Very helpful.
However i have a few problems a cannot resolve and I would be very happy for all the tips i can get.
The motor is 1az-fe (2002 car with ATM and 4x4) and was installed two years ago as a complete renewed unit.
The problems started with a p0304 code a few months ago. The code happends a bit random.
The code reader shows the misfiring on cyl 4 but also some occasionally on the others.
I tought it could be the coil and swapped it. No change. Changed the plugs and airfilter. No change.
Changed all the injectors with new ones. No change.
The motor did not use oil. There are no oil in the cooling water (or water in the oil).
I've checked compression on all cylinder - its ok. Plan to do a cylinder leakage test later if I dont find another cause for the P0304
Decided to change the oilfilter and the oil also when I was doing all this work.
I have newer had any oil pressure problems earlier. Changed the filter and filled oil. No problem so far.
Thought however it too a bit longer for the oil lamp to go out but thought is was due to the change.
Not been driving much due to the P0304 fault. Maybe 10-15 miles for testing. Also some idle.
Then I noticed that the oil lamp started to flicker and did not stop even if I reved the engine.
Thought the switch was gone and replaced it. No change. I hooked up a pressure reader and the pressure
is about 5-6 psi. the switch lights the oil lamp at approx 3 psi (stamped on the switch 0,2 bar).
When the engine is warm the lights starts to flicker and the oil pressure do not rise with higher revs.
There are no knocking sounds from the engine. Today I drained the oil. Completly fine and no metal. (the first oil I drained was also fine - black but fine)
Removed the oilfilter for inspection. Lowered the oilpan - no sludge - no metal - all looks fine. The
intake screen on the pump is fine - no sludge. Did flush with pressurized air through the oil pressure switch mounting hole
to check if it was clogged. Air flows fine down to the oil filter and out (no filter mounted). I'm going to check the
overpressure valve in the pump tomorrow. The 27 mm plug was stuck so I need to get me a breakerbar.
I going to replace the oil filter, fill with new oil. But what is going on ? Any idea ? Bad oilfilter ? Bad oil pump (motor milage after replaced approx 15000 miles) ? Anyhing else ? Oiltype (filled syntetic 5W-30) ?
I did not remove the pump because all papers I've read say You also need to remove the timing chain.... ?
This I do not understand because the pump, sprocket, chain etc are reachable from the underside ??
A lot of text - so down to two things : P0304 and next to nothing oilpressure. Ideas ??
Concerning the P0304. STFT is around 0 (-2/+2%) on both banks. LTFT is on bank 1, around -17% and bank 2, around -13%.