help with CEL P0171 & P0300 for 2000 Corolla!!

[palbuddy]

Codes: P0171 system too lean, and P0300 misfire.

Symptoms:
1. found oil on the spark plug threads(not on the electrodes), all four of them. But no oil was found in the spark plug tubes. Could this be linked to the worn valve cover gasket? Or the oil was pulled into the combustion from underneath(piston, head, etc.) The Oil level drop is noticed, and it is apparent that the engine is burning oil.

2. Poor acceleration: when hit the gas, it takes about 3 seconds for the speed to react. It feels like something is holding and release the tachometer during the 3 seconds. But the speed can go up to 80 mph without any problem. It is just the slow response when pressing the gas pedal.

3. MAF cleaned and checked. This source can be excluded, no improvement.

4. Seafoam was applied through the brake boost hose recently, no improvement.

5. PCV valve replaced, , no improvement.

6. O2 sensor replaced, , no improvement.

Could anyone give me a hint or similar experience? Thanks a bunch!

[palbuddy]

I want to add this:

The ignition is normal when the engine is cold, but it cranks badly after I drive a couple of miles. I found this by trying to ignite right after I shut off the engine after some high-speed drive. The engine cranked like coughing but it finally started.

Originally Posted by palbuddy

Codes: P0171 system too lean, and P0300 misfire.

Symptoms:
1. found oil on the spark plug threads(not on the electrodes), all four of them. But no oil was found in the spark plug tubes. Could this be linked to the worn valve cover gasket? Or the oil was pulled into the combustion from underneath(piston, head, etc.) The Oil level drop is noticed, and it is apparent that the engine is burning oil.

2. Poor acceleration: when hit the gas, it takes about 3 seconds for the speed to react. It feels like something is holding and release the tachometer during the 3 seconds. But the speed can go up to 80 mph without any problem. It is just the slow response when pressing the gas pedal.

3. MAF cleaned and checked. This source can be excluded, no improvement.

4. Seafoam was applied through the brake boost hose recently, no improvement.

5. PCV valve replaced, , no improvement.

6. O2 sensor replaced, , no improvement.

Could anyone give me a hint or similar experience? Thanks a bunch!

[laramarvin]

You could also check:


Engine coolant temperature sensor

Fuel pressure

Gas leakage in exhaust system

Let me know if this helps.

[BigTDogg (MA)]

Originally Posted by palbuddy

C
3. MAF cleaned and checked. This source can be excluded, no improvement.

Did you spray the red area too? Get it all up in there. That's what cured my P0171

[SBUBandit]

wouldn't it be nice if you could try new parts like MAF sensors before paying for them. Then you could throw a new MAF on, and if it didn't fix it oh well, give it back. My car has the same problem by the way. I was thinking o2 sensor, but maybe not. Hopefully I will be able to figure it out once I get my new Actron 9190. Hopefully I can see the sensor readings live on it and figure out what is going on

[Buurin]

P0300 is random misfire. Test the spark plugs. If all plugs fired strong, look at the fuel system.