Ok its has been awile now and i still cannot figure this out. P0300 cel comes on for 3-4 days at a time and clears its self for about the same time. When it is off it runs like a champ. When it is on i get a lump on cold starts but not everytime. Mostly its not even noticable every once in a wile their is a noticable chug chug to it. But it always smoothes out once it warms up a for a min. It affects power and mpg just slightly when it on. I have aprox 212,000miles on her. Bone stock no mods. New maf sensor new o2 sensor new fuel filter new spark plugs new ingntion coils new wire set. Timing was done at 209000 miles. Please help i love this truck and i dont want it to take a crap on me I cant afford it.

 

Was this happening before you replaced the plugs, wires, and coils? Could be injector issue, compression low. Maybe burnt exhaust valve. Have you ever adjusted the valve clearances? Done a compression test?

 

Yes everything got replaced because of the problem. I sent it to a shop the engine is fine no compression issues or valve issues. The code cleared itself and they told me it was fine which i half expected to happen i explained the situation he said there was nothing they could do to figure it out unless the cel was lit. So i would have to come back and spend another 85$ i dont have.

 

Everything is prestine with this truck apart from this code i refuse to lose!

 

You have a p0300 only? I would expect it to be accompanied by a more specific code like p0303(cylinder 3 misfire). Maybe there is a pending code as well as a hard code.
The problem occurs when cold only? Could be a leaky injector thats dripping into a cylinder after you shut it off and it sits.
I would do a cold compression test and closely inspect the plugs at the same time.

 

They said p0303 did pop but they found no problem. Pretty sure they did a cold compression. Would that show if i have a leaky injector? Is it possible that their is somthing at fault with my ecu? I was running a code when i swapped the coils and discovered that pull the negative cleared the code for that 3-4 day window is it possible that my ecu is to blame?

 

ECU is not the problem. P0303 means a cylinder 3 misfire. Now you can start diagnosing. Its very easy. I know you replaced a bunch of stuff already but start swapping parts and this will be rather painless. Write everything down when you swap parts. For example, Swap #3 and #1 coils. Swap #3 and #2 spark plugs. Swap #3 and #5 injectors. Then drive it and wait for the light to come back on. If you still have a p0303 you know its either a mechanical problem with the engine or wiring issue to the coil or injector(very rare). If you now have a p0301, you know its the coil, if you now have a p0302, its the spark plug, and if you now have a p0305, its the injector.

 

^^^Try what he said. If no luck: the first issue in the FSM P0300 list is the PCV valve. Worth a check. Since warm-up issue is mentioned, also check the Engine Coolant Temp. sensor. If wrong mixture is being sent at start-up due to bad temp. data, misfires can happen. The Freeze Frame data can be a big help here if you can get it.

http://tacoma.site40.net/4Runner_96-...e/cip0300p.pdf

 

P0300 or P0303... which is it!

P0300: Random Multiple Miss fire(s) detected.

P0303: Cyldiner #3 Miss fire detected.

If you have P0300 I would inspect spark plugs for proper gap and torque.

Engine oil level correct..?

Engine coolant level correct..?

Crankshaft vibration damper(Crankshaft pulley) damaged and or "wobbling?"

If P0303 alone... possible weak ignition coil...?

A faulty PCV system can also cause this as previously mentioned. <--(P0300)

 

Ok thanks guys i will take this into account and start running through these options.

I did just find my radiator res. cap loose. Could that create a lack of pressure that would cause a misfire? I dont think i have opened that cap in some time. Plus my fluid looks low... damn i suck at life i can work on most anything on vehicles but always forget about the darn coolant. Fml

 

Loose radiator cap will not cause any drivability issues