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 like new 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

 

Pull your spark plug wires for 2,4,&6, and look at the plastic tubes for burn marks and sign of arcing. I just had to replace mine today after a week of trying to figure out a miss

 

they are all replaced + i just bought a new maf sensor still no luck

 

Could it be the fuel pump? You are running out of things to replace!

 

p0300 is random/multiple misfire

You've been through the basic stuff...

Has timing belt been replaced? I've seen the crank bolt not torqued and it comes loose, allows the pulleys to walk out a little and wear on the keyway...what happens is the crank timing pulley which is used for the crank sensor starts to move around and the crank sensor won't read it right. Sometimes it doesn't happen bad enough to set any crank or cam sensor codes but it will cause a misfire.

Its a possibility , just giving you another area to look at.

Good luck

 

That wouldn't be a fun investigation. If it comes down to looking at the timing, you might as well replace the belt, pulleys, and water pump.

 

It's not fun, cause when that happens the timing pulley is usually stuck on the crank