Tacoma running rough no CEL

I have been mostly lurking around here when I am having a problem with my Tacoma and need information. This site has been a great place to learn and help me figure out what kind of issue I have and what it takes to fix it.

Currently my problem is a rough idle/miss

I took it by and had codes read, can't remember exact code but it was cylinder #2 misfire. I took it to the house and pulled plug and it looked fine so I checked wires and they looked good too. Wires and plugs only have about 40K on them
So I got on here and started reading and searching
Found a thread with similar issue and one of the suggestions was to clean the MAF. Being that is cheap I cleaned it, put it back together and it ran like a top, for a few days.
Then it started up again and as I was trying to get home without the CEL flashing (understand that is bad) it just cleared up and ran fine again????

I decided that the MAF must be bad and not just dirty so I changed it out and cleaned the throttle body real good and again it ran fine

All this time there has been no CEL constantly on, just starts flashing and I go into limp mode and it goes off

So I drove it about 7mi into town to get some fuel for the ATV and generator and filled it up with premium and 1/2 a can of seafoam.
When I cranked it back up at the gas station it was missing again

All this to ask what would cold start and run fine but if restarted warm would run rough?

I read similar threads and bad EGR or ECT came up but I don't want to start throwing money at random things hoping to get lucky before going broke either.

The other thing is the fact it cleared up in the middle of one of these episodes

All injectors were replaced a few years ago but I can't find receipt to determine exactly how long ago it was

I am no mechanic but I am mechanically inclined and not scared to attempt to fix anything. I have trailered stuff to the mechanic a few times after my attempts to fix were unsuccessful

Appreciate any and all help

 

One thing that can help your path is make sure there are ZERO vacuum leaks,

Any vacuum hose that is not tight or is old and a crack will cause tons of problems.

Even the smallest of a vacuum leak!,,

Where did you get new MAF from?

Get one from the dealership.
Typical MAF is not a misfire related tho


There are fake ones everywhere,

Misfire=
Plugs
Wires
Carbon tracking
Coils
Vacuum issues
Injectors
Head gasket or antifreeze getting pass head gasket

 

Depending on the type of plugs, 40k can be a lot. I had a misfire that was caused by carbon tracks on the plug wire tube (the part that goes into the valve cover, whatever it’s called). I cleaned it thoroughly and replaced the rubber seals and boots, along with new plugs, which solved the misfire.

I don’t understand how a bad MAF sensor could cause a misfire; should just run in open loop, no?

 

MAF came from Oreilly's, only reason I changed it is because after cleaning the old one it ran like a scalded dog

Vacuum leak is a possibility, will gather some lengths of hose and start checking/replacing

Would not think head gasket would run good any OR clear up in the middle of an event?

Appreciate the list and will go through all of it as I can

I don't understand it either but like I said above, ran fine after cleaning????



Thanks for the reply, I appreciate it


Did locate receipt, injectors are just shy of 3yrs old. Replaced the whole set in late March of 2018

 

Can you make it miss in the driveway with the hood open? Do so after dark and look for arching along ignition components.

 

At some point if you can't find the problem a compression check would be good.

The flashing CEL means there is a misfire and unburned gas is going into the catalytic converter, so it's a warning that you could damage the cat if you drive too long like that.

 

When you say “limp mode” do you mean
the truck is way down on power when this happens? Struggles to rev past 2500 or so?

 

Op from what your saying cold starts seem to work ok?

Once the truck gets shut off when restarted again it runs rough to it clears out.

The plug looked fine your sure? Almost sounds like a leaky injector is fouling the plug then it clears up.

 

Strong possibility I could since it seems to be more likely to start showing up after engine has come up to temp, been shut down and restarted

When I say limp mode, I mean I drive it easy to make it back home.
But yes it loses power and the CEL will start flashing around 2500rpm when it does decide to come on.

Went out and cranked it up this morning, 35 deg, let it warm up and drove it 22mi to work with zero issues.
Got in it and drove it home after work, around 65 deg, and made it about 15mi before it started loosing power and struggling. Babied it on home and no CEL but sounded like a bad exhaust leak but may have been due to missing


Work tomorrow looks light so planning to take it by mechanic and see if he can hook it up to the analyzer /code reader he has and shed some light on it. It can tell all kinds of stuff that might help figure it out.

 

Code for cyl. 2 misfire is P302. That isolates it to one cylinder. It's either ignition, fuel or a mechanical issue that causes the misfire. Like the others have said, the MAF doesn't cause a misfire. if it did, it would not isolate to 1 cylinder, it reads the air flow for all cylinders.
Most people put a new set of plugs in when the get the P300, P301-304 codes. It is the easiest thing to do. If that doesn't fix it, then see if the miss will move to another cylinder by swapping coil packs (unless you have a distributor). If that doesn't do anything, then check fuel system or mechanical. mechanical is compression, so a compression test will tell you a lot.

 

My truck had very similar symptoms about a year ago and took me longer than I’d like to admit to figure it out.
what fixed mine was the “air/fuel sensor” located before the cat converter in what would typically be called bank one sensor one..
It looks just like a typical O2 sensor but has much more control over how the truck runs. Its relatively expensive 140 or so but if ya can’t find anything else wrong I bet that’s it.

 

Light case load at work this morning so headed to mechanic around 7 and see if he can get codes (still no CEL) and maybe his fancy little gizmo can diagnose issue. He is running a small shop and supportive of me doing my own work. I still end up paying him to fix all kinds of stuff from tractors to trucks and send him a lot of business from others

I would rather have something broke than work sometimes and sometimes cause problems

When I replaced injectors I bought a "matched set" from a place in Arizona I think, CE something I think. Thinking was if I was already far enough in to get 1 injector I might as well change them all.
If it turns out to be an injector, how much difference can it make to just buy a reputable brand and replace the one?
In other words, is there any benefit to even buying a "matched" set when replacing?

 

Drove it to mechanics about 3mi down the road

Left it idling and went inside and talked about 10min, came out and idling rough / missing.

Hooked it up and got cylinder 2 misfire code only

Drove it back to house and took wife's car and go new plug, no change.

Swapped coils, no change

Have to go to work, closed hood and forgot flashlight was laying under hinge . Now hinge warped and hood back corner about 1/4-5/16 out of whack. Wil worry about getting that right after I figure out misfire.

Going to check wire and possibly swap if I still have old set and see if that helps.

Next step will be compression check, then injector I guess because that is the easiest and cheapest order

Thanks again for all the help

 

Sorry to hear about the hood incident...hopefully it's easy to fix and your story will serve as a reminder to someone else to double check before closing the hood.

Which engine do you have (sorry if you already posted this info)? When you say you swapped coils, do you mean you put a new one, or just reversed the position of two coils? If you just reversed two, could it be that the misfire followed the coil but the ECU didn't update? Are you sure your understanding of cyl 2 is the same as the ECU's understand of cyl 2?

 

3400 6 cylinder
My understanding of cylinder 2 is the front cylinder on the driver's side bank?
Passenger side odd 1-3-5, driver side even 2-4-6

I had a new coil to switch out, otherwise I would have to drive it back down to the mechanic and trouble him

Did some reading this evening and seems the most likely suspect is the injector. Seems there is a little electrical part that does not hold up well. Plan was to pull it apart and get it back together Saturday in the driveway but chances of rain starting Thursday through the weekend nixed that idea.

Luckily the hinge bent and not the hood (at least as far as I can tell) and that should be fixable

 

Pretty much ruled out spark system tonight.

Checked resistance on coil pack and it checked out
Pulled wire off of plug on #2 cylinder and plugged spare spark plug in and it was putting out enough juice to jump across 1" or greater gap to ground
Engine cannot run on 4 cylinders, with active miss on #2 I pulled connector to coil pack on #5 that runs both and engine died

Also found a poor man's method of checking to see if injectors firing with a long screwdriver, tip on injector and your ear on the other end you can hear it clicking. Compared to other injector on opposite bank and pretty much making identical ticking sounds.

I also talked to Tony @ LC Engineering (where I bought injectors at 3 years ago) via email and he inquired about changing filter and ruling out fuel pressure regulator before going into depth of injectors.

So fuel filter swap (about due for it anyway) and figuring out how to check fuel regulator is on the list of steps now.
Supposed to start raining tomorrow so it might be after that stops that I get to do the filter swap and fuel pressure test.

 

I'm not sure if your spark test can effectively rule out a short to ground when it's installed, like from a bad wire/boot. A misfire caused by a short to ground is absolutely consistent with a healthy coil, since spark will always take the path of least resistance. Upstream fuel system is a possible culprit I suppose, but it's hard for me to understand why the problem would consistently be isolated to the same cylinder, unless some crap is intermittently clogging that part of the fuel rail. Did you ever pull the cyl 2 plug right after it was missing to see if it was wet with fuel?

 

what he said. Good points. It looks to me like you should look for a mechanical source. Do a compression check, it's very likely valves or head gasket.

 

I can certainly pull plug right after missing and check for fuel

My feeling last night was trash in the injector possibly

Might be the weekend before I can do a compression check with weather that is supposed to be coming

 

Compression check is a good idea...any other clues that could point to a head gasket, like frothy oil or sweet smelling exhaust? Losing coolant?