P0301 misfire on cylinder 1.

Looking for the input on a problem that has recently come up on my 2003 2.7L tacoma. Recently my CEL came on, read the code, P0301, misfire on cylinder 1. I never felt anything or noticed it misfiring but code came up. I reset the code, a day later it came back on, i replaced all 4 spark plugs, i have not replaced the coil packs, but i have a set on the way. I did test the coil pack on cylinder 1 by pulling it while the engine is running and the engine does misfire and run like shit when pulled and when restored runs fine. I ohm'd out the injector on cylinder 1 and it was reading 15.8, for reference i checked cylinder 2 injector and it was 16 point something. I have not cleaned the MAF, will clean it tomorrow. Other then the MAF, everything i have tested shows the plugs are fine, the coil pack is fine or intermittently not firing the spark plug, the injector is fine. I have not done a compression test on cylinder 1, i will pickup a compression gauge tomorrow and test its compression, the truck has 203,000+ miles on it.

I have seen the CEL turn itself off without me resetting the code, however as of right now it is on. I have seen the CEL flash, which tells me unspent fuel is dumping in the CAT, which i have read that not to be a good thing.

I also every so often have a loss of power from a dead stop (this has been going on for the last 50,000 miles or so), i will get a green light and press on the gas peddle and the truck will hesitate to go, it will go but like theirs no power, then after a few seconds it picks up and goes like normal. The truck also seems to have lost power over the 100,000 miles iv put on it since i purchased it used, although i have put 1 size bigger tires, lift spacers on the front, replaced the front stock bumper with a custom made one which is not too much heavier then the stock one, and put a new muffler on.

 

BTW, an injector can ohm-out properly but still be bad. Don't rule that out yet. Have you tried injector cleaner ?

 

Sounds like you are on the right path. I am having very similar issues with my Camry right now, at a wall and the dealer getting it looked at.

A misfire can be caused be a few things, and if the computer detects the issue is not occurring can clear the CEL. You may not have an issue with the coil pack at all - could be something else causing the misfire. I figure it it is always the Holy Trinity: Air, Fuel, Spark. Sounds like you are ruling out Spark. The injector can be clogged, so the ohm reading can be fine. The FSM walks you through checking the injector - might be worth a shot.

 

I have done the fuel injector cleaner, not recently but withen the last 4 months.

 

So my issue looks like it may have been bad gas. The dealer took $186 of my hard earned coin for a diagnostic that they went "we dunno, can't find anything specific". I had no CELs, unlike you. But, I was misfiring like a sun of a gun, just no codes.

Has it been one tank of gas?

 

I did swap the coil packs around between 1 and 4 and got a CEL P0301 misfire on cylinder 1. So next round is changing that injector.

 

You may want to be prepared and have new o-rings ready. If you plan to just swap injector 1 to another spot to see if the problem moves, then you will be pulling 2 of them, so have at least 2 packs ready. Sucks to have it pulled and find you now had a bad o-ring, so another trip to a parts store (that may not have it in stock). You don't want a fuel leak added to the mix. Even the dealer price is OK on these o-rings. They claim the insulator is another component you change when doing this kind of work.

 

Finally had some time, did a compression test,

#1: 163psi, #2: 155psi, #3: 147psi, #4: 165psi

 

Those are good numbers. So that narrows it to fuel or ignition.

Have you changed the spark plugs?

 

What brand plugs are you running?

Bosch Plugs will give you a code 301.
I've been told that Toyota Electrics want to see Denso or NGK Plugs.
My misfire code was the result of two burned valves, was running cheap Arco gas. Made it to 284,000 miles before replacing engine.

 

I use the NGK plugs.

I have now replaced all 4 injectors, and am still experiencing the p0301, i also get a p0171 after the injector replacement.

I only experience a p0301 when the engine is cold from sitting parked over night, if i dont let the engine warm up i get a p0301 misfire on cylinder 1, if i let the engine warm up i do not get a p0301 or flashing CEL.

 

I have a Tacoma V6 3.4, I had an issue with power taking off and building up speed but then it would go like normal.

("hesitate to go, it will go but like theirs no power, then after a few seconds it picks up and goes like normal")

Like yours mine did it for thousands of miles as well. Replaced the valve that sits on top of the gas tank and my issue/probelm went away.

 

"Hesitate to go, it will go but like theirs no power, then after a few seconds it picks up and goes like normal."

Check the valve that's on top of your gas tank. Replacing valve and cleaning trottle body cured mine.

 

when she is stone cold, open the hood and take the radiator cap off, start her and see if there are any bubbles coming up or get a combustion gas analyzer done on her... I think you might have a weepy head gasket.

 

"Hesitate to go, it will go but like theirs no power, then after a few seconds it picks up and goes like normal."

My 99 Tacoma is doing the same thing. You guys mentioned a valve on top of the gas tank? Can you explain this a little more not sure what you are talking about.

 

Here’s what I did in order of steps I took to diagnose the problems, I’m sure others have already mentioned it but I’m just laying it out there. You may stop at an earlier step than I did, I went fairly deep.

1. Check for smoke or coolant leaks, if your radiator is hot and/or you have coolant leaking and smoke, you may have blown head gasket. That’s a whole other issue and you probably would’ve realized it by now....

2. If not step one, check for any loose cables or hose connections on the exterior of your plenums.

3. if not step two, check your plug wires that connect to your coils. Now, I don’t really know any other way of doing this other than if you see any loose connections along the wire where it connects to coil or on drivers side, OR if you swap coils 1&3 or 3&5 or 2&4, etc... If you swap the coils and instead having cylinder 1 misfire, let’s say, and now cylinder 3 is misfiring, then you have a bad coil on for cylinder 1.

4. If not 3, then you are going to have to take apart some things, could be injectors or a valve is too tight (which you can adjust). You will have to remove intake, throttle body, all the hoses connecting to the upper and lower plenums, then remove the upper and lower plenums. You will then have to remove the injector rail, but before doing that I recommend pulling the fuel line out of the back of it, and putting a shop towel at front end for the fuel that will leak. Then you remove the injectors by their clips and you should be able to tell what the issue is with them. My injector on cylinder 1 was warped and the threads were all worn out on it. So I bought a new injector (didn’t have money to do all of them), and replaced all the O-Rings on the injectors that I inspected (all of them). You have to replace the O-Rings when you remove injectors, otherwise you risk leaks later on after they’ve been removed once.

Step four Is where I stopped, I wasn’t getting proper injection to cylinder one. Was hoping I just had to clean it but had a deeper set of issues. Hope this helps!

 

How the Hell does it determine a particular cylinder is misfiring?

 

Believe it or not you can actually feel the coil discharge into the plugs by gently holding the wire between your fingertips.

 

Doesn’t exactly determine if a cylinder is misfiring. I knew my cylinder was misfiring before taking these steps. This list of steps was a way of troubleshooting the cause of my misfire. For example, the coil swap, that’s a good way of determining if it’s the coil that is going bad if your code reader says (post swap) that cylinder three is misfiring instead of cylinder one like before. Make sense?

 

Damn this thread brings back hair pulling memories of my Ford Ranger... Glad I have some warranty left and good luck to you.

1st time turned out to be a clogged injector so $50 bucks (Rangers were so cheap to fix) and I was back on the road after much cursing.

2nd time it was a cracked spark plug wire that was arcing only sometimes. Enough to set off the CEL but not enough to really notice rough running.

3rd time was another injector (of course also on the bank under the aluminum intake manifold). Replaced the remaining 2 that time. Also had one plastic cap from the injector fall into the cylinder so my engine just ate that...