engine code p0300

2002 tacoma 2.7l 4x4, about 2 week ago i had the engine light comes on.
plug in the scanner and pulled out code p0300. go on Google and found out that I had a random multiple misfires. truck seem to run fine when rpm is above 1000, but the truck shake while idle and rpm drop to 7-800.

don't know what's the causes, but this is what i have done so far replaced with both new 02 Denso sensors, replace new sets of Denso plugs and Denso ignition coils. runs ok after the replacement seem to solve the probems.

2 day later the the truck shake and the light turns back on, check and pull out the same code p0300, now it goes back to squar 1.

is any1 here have this kind of issues with their trucks? and what u do to fix it? your knowledges and experiences are greatly appreciated, thks.

 

if you are sure that the ignition system is OK, then look at the fuel system. it is possible to get brand new parts that are defective.

 

right, i need to go back and check all the plugs and wires may be on the weekend i work on the week days. yesterday i spent 2 hours checking all hoses connections and did not find any fluid/air blockage. also removed air filter housing and pressurize a thourough clean and also replace with a new k&n filter. this wasn't help either. my next step is to check for air leak, fuel systems and so on. will keep u guys update with the issues.

 

Try cleaning the MAF sensor, I had the same exact problem. I changed the air filter, cleaned the throttle body and thought I had it solved. Then 2 days later same problem again. Rough idle and engine hesitation when you hit the gas. Before changing the spark plugs I cleaned the MAF filter and its been fine ever since, this was 3 days ago. Truck running way smoother, and even gas mileage improved! Be sure you use MAF sensor cleaner or electronic contact cleaner only, and be sure it's completely dry and free of residue when you reinstall it. There are a number of videos on YouTube on how to do this. Some suggest using alcohol and q-tips but I think the safer bet is MAF sensor cleaner cause you avoid having to touch it a whole lot, the spray does all the work. Total time 30-45 min, less than 10 bucks spent.

 

Did you change plug wires? If not, check the resistance of each wire. I think they are supposed to be between 15,000 and 25,000 ohms. Also check the gaps on your brand new plugs. I've seen "pre-gapped" plugs (factory Toyota NGK) be improperly gapped out of the box. Both issues could be your culprit.

 

i did the leak down test and found out that i had some leak inside plug 1 an plug 2. plug 1 test result is 90 and plug 2 is 145. plug 3&4 are 157 and up.
now since the truck is 157k + miles i was thinking of replace with new cylinder head, new timing chain and water pump. found out that this timing chain is only good up to 150k miles after that it starts to get loose, chip and extended in over time. i will keep this update when the issue is fixed. thanks for the inputs.

 

alrite, after couple of weeks i finally fixed the code P0300. the long process and the right way it was pricey but worth it. long make it short, i stripped out the motor and found i had a cracked piston on cylinder 2. I pour water on manifold ports and exhaust ports and they all leak water run down the piston like running river, what a gunk. i decided to buy a new cylinder head to swap out the bad. took me 3 hours to disconnect and unbolt everything to be able to remove the bad cylinder head from the motor. and another 8+ hours to connect, assembly new head and bolt everything back together. The new head works like a champ it starts up at the first time when i turn the key, what a relief! truck is very stable feel like brand new from dealer.
I download Auto Zone instruction manual for the guide but when it comes to bolt the new head onto the motor it says to torch all bolts to 29ft pound. i ignore it and went ahead torch all my bolts to 50 ft pound. my reason, as time go by the new head gasket might shrink and water might sink into the plugs that why i decide to heavier torch all bolts. all parts, wires and hoses are double check for fitment and correct connections. take pictures is the smart way to help with putting things back where they belong.
the cost for replacement parts:
new front and rear 02 sensors-$298
new set of ignition coil;$267
new ngk plugs-$21
k&n air filter-$46
bosch oil filter -$6
oil castro gtx 5-30 partial sintectic -$37
10 galons of anti freeze -$28
head gasket-$49
intake gasket-$14
exhaust gasket-$11
altonator belt-$20
power steering belt-$16
a/c belt-$20
new cylinder head +tax+shipping-$613
1 tube of heat treat silicone-$6
now you figure out the total cost.
some of the parts above are not necesarilly to replace but i just replace them because they are in bad shape. the truck is now 11 year old. i might be good for the next 150k miles. hooray!!!!!!!!!!!!!!!!!!!!!!! engine code P0300 is gone!

 

Glad you got it fixed. If it was a bad piston, why did you replace the cylinder head? And how do you put 10 gallons of anti-freeze in your truck?

As for the torque (NOT TORCH) on the head bolts, make sure you always follow the manufacturer's instructions. (not saying that Autozone had the right info). you could snap the bolts by over torqueing!

 

Dude no way! it was a cylinder head I just got the same code on my 3.4

 

Did you figure yours out? I just got the same code in my 3.4. Hope its not the cylinder.

 

I tried replacing my fuel pump, fuel filter and spark plugs and the code is still there. I pulled my injectors and having them cleaned and rebuilt right now. Once I get them back I'm going to do a compression test. I haven't figure it out yet.

 

How long have you had the code? and has any more popped up?
Mine is a pending code right now and the rough idle started happening a few months back but only today it went in to my scanner as a pending code.
Reading some other forums some guys have other codes come up later on which leads to a specific cylinder.

 

I got the code back in Nov time frame but I parked the truck. In Dec I changed the fuel pump with no luck. Money is tight during winter. That's the reason why I waited this long to try and fix it. No other codes came up. Still the same one. I should get my injectors back in a couple of weeks. I also have new wires too. Once I get everything back together I'll do a compression test and test drive it to see what happens. It will be a few weeks before I have anymore info for ya. Once I find out I'll let you know.

 

Im still driving mine. It still only in my ultra gauge as a pending code and the check engine light hasn't came on yet.
I have new spark plugs and wires that I was planning to install, might start off with that to see if the problem goes away.

 

Pulled my coil packs today to test them and found my #1 where the wire plugs into covered with corrosion. Cleaned it off and tested them. They are all about the same. I still won’t find out for sure if this is the issue until I get my injectors back. The wire was covered with corrosion too. Test was with cold coils. I don’t know if I did the test right. I went off auto zone website