02 4runner sr5 sport with 210,000+ miles (stock). Lumps at idol at random mostly after it was ran for a few min and restarted. Replaced all coil pack, spark plugs, fuel filter and the o2 sensor. Sprays carb cleaner all over trying to find a vac leak to no avail. Cleaned the maf sensor but still no better. Every time I clear the code by removing the negative battery lead (P0300) it runs perfect for about 2 or 3 days then the dash lights up once again and the lump returns. Tired of throwing money at it please help

Why does the misfire go away when i clear it? Is my ECU fried?

P0300
lean air/fuel ratio-fuel pump
faulty maf/vaf sensor
large vacuum leak
Ignition system fault

 

All right when you clear the code it does not really fix the problem.

now it takes the 2 or 3 days of driving to trip the MIL again .

This is where a scanner comes in so handy to read data in real time

The diagnostics section in the FSM are a great help in a time like this.

This is a random problem causing a misfire. That is intermittent which is even
moreof a pain to find.
could be almost anything loose or corroded connection a worn wire causing a problem as it flexes .

Could very well be the ECM

 

No what i meant when I said it fixes the problem is that it really does. For those 2 3 days it runs like its brand new. Then all of a sudden it will go back to the misfires and the light will come on.

 

Have you tested the ECM??

I have never been lucky enough to cure a problem just by clearing the codes.

 

No i have not i am not quite sure how to go about it. Yeah to bad the problem comes back every time.