P0301 Code

Hey guys,

Had code P0301 Misfire Detected at Cylinder 1 pop up a couple of days ago. Replaced the spark plugs and wires last night but still have the engine light on. Air filter is clean. I notice it is harder to get up to speed on the freeway. Feels like the truck jitters some when driving. Lost around 3 gallons (fuel indicator was about a quarter down from full and kind of gitters when in idle) of gas from filling it up last night to getting to work this morning (probably 35 miles total).

• Didn't see any sparking from the old wires at cylinder 1 or any at the coils so I'm not sure if it's the coils or not? Could it be a fuel injector?
• I'm running some seafoam into the tank right now so we'll see if that helps it out.
• Noticed a lot of corrosion on my battery positive terminal and noticed it doesn't have the best connection so I will clean and fix that up today. Maybe that could fix it?
• Someone at the parts store today overheard my code and said he just had the same thing happen to his V6 (mine's a 4L) and what fixed his problem was a bad connection/corrosion to the alternator but I can't see that bad of a connection with mine or any at all.

Any advice, experiences or guidance is much appreciated!

 

Do you have 4 coils or a distributer?

 

Your profile says you have a 2.7 (4 cylinder 3rz), not a 4.0

 

Looks like CA emissions vehicles have coil-on-plug, Federal emissions appears it has a coil with two plug wire connectors (looking at RockAuto photos). Does the 2.7 have 2 plugs per cylinder, or just one? I know Nissan used to do that 2 plug thing. Anyway, if you have done plugs and wires, the coil or coil pack is what I would look at next. You could swap coils and see if the code changes to another cylinder.

 

Heres pictures of what I think you’re wondering? I thought 4.0 meant 4 cylinder. This truck is California emissions specified.

 

Looks like you have Federal emissions, those are your coil packs in the second picture that the plug wires are going into. I thought you said you replaced wires? Those don't look new, lol, hopefully that's an old picture.

I thought you could swap those 2 coils as a test, but it looks like they might be specific to the cylinders. It looks like AutoZone typically stocks their Duralast brand for $68 each and they say it is for all cylinders. You could get 2 from RockAuto for that price, but they have them split for cylinders 1,4 and 2,3, which matches your wires. They do have a Delphi branded one for all cylinders, though. If you can wait, order from RockAuto (they are listed under vendors here on TW and have a coupon code), or get one locally if you can find one and replace that front one, see if that gets you going. Make sure your wiring is good first, though, to rule that out (check to make sure the wires going into the side of the coil pack aren't broken or pulled out of the connector).

 

Haha yeah that’s with the old ones plugged in. I have the code erased to see if it may come back on/other codes come up. Which one would I get from Rock Auto that will work for my truck?

Appreciate the help!

 

Sure thing, if you want to go cheap:

WORLD POWER SYSTEMS CUF180 is for cylinders 1,4 (the one toward the front of the truck), CUF181 is for 2,3. If you only get a 301 or 304 code, you can just do that one to see if that fixes it. If it does, I would follow with the other one. Or just do both at the same time, I assume there are lots of miles on that truck, and it's less than $50 for both.

If you want to go with OEM, they were most likely Denso, that would be part

$44 DENSO 6731100 Denso Direct Ignition Coil OE Quality - 673-1100

DENSO 6731100 for 1,4 and 6731102 for 2,3. They run about $52 each, and it looks like you can order them through AutoZone as well for just a little more.

 

Yeah there’s around 208,000 miles on it. Would you trust the part from rock auto for a good time of not going out or failing?

 

I would count on it to last a good 30K miles minimum if not more, and it's probably about the same as the Duralast branded ones. Personally, I would buy the Denso, but I have trust issues.

 

FYI- Tacomas have a V6 or I4 (you have an I4). The letter refers to the shape of your cylinders, "I" stands for In-line. The number references the amount of cylinders. When you start using the period and/or L for litters, you are taking about the actual volume of the the engine. 2.7L or 3.4L as two examples.




Here is a thread about testing your coil pack..... TLDR; Call and see if any of your local auto parts store can test them.


I buy from RockAuto all the time, I would trust them, especially if you buy something with the little heart next to it. The downside to RockAuto is shipping, you either wait a long time, or pay a ton for shipping, which negates any savings over buying local. Also, when you are looking for the best deal on OEM parts, check out Camelback Toyota, even with shipping the cheapest dealership in the country. They have a thread on here for you to get quotes and ask questions. Some things for older trucks are stupid expensive and other things are surprisingly cheap, you just don't know until you ask.

 

Just keep in mind, there are a couple of other components of the ignition system that can be at fault, crankshaft position sensor and camshaft position sensor. Both are also reasonably inexpensive, although I am not sure how complex the install would be. From the looks of the parts, they should be accessible. If you can rule out the coil pack, those are the next places to look. Starting cheap with plugs and wires is good, though.

I'm not sure if the code will move around on cylinders if it is either of the position sensors. With those coil packs, I would expect a 301 and 304 combination (or alternating) or a 302 and 303 combination if it's the other one that is bad. If you get a code from each set, it's not likely that both coils are bad (but possible) and I would look at the other sensors.

When I run into things like this, I just order all the parts and replace them all, LOL.

 

I do this too.

 

Last time I got a P0301 code was when I had 0 psi compression on #1 cylinder. :0 You would probably be able to tell cause it would be missing horribly and running super rough, but have you done a compression test yet?

 

Just did a diagnostic today and the compression test is fine. They said they diagnosed it to be the number two fuel injector and gave me their reason why. Why would I get a cylinder 1 misfire code and have a clogged up fuel injector 2? I called another mechanic and he says that he’s never heard of that before. I’m growing old of this

 

Did you already do coil packs or confirm that you are getting spark? It's gotta be either fuel, air or spark, and I think air is ruled out. Those codes seem to be pretty accurate, at least on the 4.0L. I did my 30K mile plug replacement and had a miss afterward, took it a little while to throw the code, but it was accurate and pointed me to the right cylinder. Plug had a hairline crack in it. Replaced it and was good to go.

 

I haven’t done coil packs because I didn’t want to keep throwing money at it until I got a diagnoses, which this one I got doesn’t make sense to me.

What do you mean by plug?

 

"plug" = spark plug. it would have had a crack in the white porcelain

https://en.wikipedia.org/wiki/Spark_plug

 

Oh duh my bad. Yeah I’ve done the spark plugs and wires and they tested it as a fuel injector #2 plugged up for a cylinder #1 misfire. Not sure how that would be.

 

Yeah, sorry, plug = spark plug.

So did it throw codes again? Same 301? No 304? My experience on other engines where the coil pack serves 2 cylinders is that both cylinders are dead when the coil pack goes out. I would think the thing would barely run on 2 cylinders and be undrivable if that was the case.

What reason did they give you for the fuel injector diagnosis? Did they validate that the coil was providing spark to #1?

Sometimes odd things happen and codes don't make sense. There was a lady on here a year ago or so that had odd codes (she had the 3.4L V-6) and it turned out to be leaky fuel injectors. I had a non-Toyota vehicle that just kept throwing random codes all over the place.

If you've got good air flow and good spark, the only thing left is fuel. The Seafoam may help if it is a clog, might try some Lucas, but if it is malfunctioning for other reasons that might not help.

Sorry, hard to diagnose stuff over the internet, but with good compression you shouldn't be too far away from a fix.