2003 Tacoma 2.4

Hello,
I have a 2003, Tacoma, 2 Dr. 2.4 base model. The truck has a rough idle and the gas mileage has dropped to about 19 MPG.
I have changed the plugs, fuel injectors and coils.
Have cleaned the Mass air flow sensor. Have removed the throttle body and cleaned it as well as the IAC valve.
Have also changed the air filter and fuel filter.
I am currently getting a misfire on number two cylinder. Have cleared the codes several times by both using the code reader and disconnecting the neg battery terminal and it keeps coming back. On rare occasions it will add a misfire on cylinder 3 and sometimes it will add a misfire on cylinder 1. These two do not happen all the time.
Other than the misfire it runs strong as a bear.
It does not show any other codes.
I am using an actron 9127c code reader. In addition to the misfire codes it will also show the following info
“4 INC” with an arrow pointing up and down.

“Catalyst” same arrows as above

“Evap” same arrows as above

“02 Snsr” same arrows as above

“02 htr” same arrows as above

“3 Ready” same arrows as above

“Misfire” same arrows as above

“Fuel” same arrows as above

“Comp” arrow is just pointing up

It is not comsuming any antifreeze, nor are there any bubbles in the coolant when I remove the radiater cap and observe the coolant.
When i connect a vacum gauge to the intake manifold the needle fluctuates back and forth rapidly indicating that it is running rich and lean. Have been unable to find any info on how this can happen.
I consider myself a pretty good mechanic but am stumped as to what is causing the misfire on cylinder two. One of the things I cannot understand is how a bad Mass air flow sensor or weak fuel pump will give a misfire indication on one cylinder concistantly.
I also ran several cans of seafoam through the fuel system.
By the way. The truck has 360,000 miles on it and has been an incredible truck up to this point.
Also this truck does not have an EGR valve. The fuel filter is mounted on the drivers side of the engine. And the vacum canister is mounted above the fuel tank.
Any help would be appreciated.

 

have you check the vsv valve yet?

 

I have the same ride as you and its sounds like you have been very thorough so far.

• Did you use all quality plugs (Denso/NGK)? Gapped them properly? Torqued them properly?
• Did you use all OEM coil packs and injectors? Swap the order of them to see to try test them out?

I would try to continue to trace the causes of the misfire (which you have done) before moving back on to the air/fuel/vacum/sensor issues (which you have done). Might be worth a professional mechanic diagnostic before throwing more parts at it.

Revisit the following threads:

https://www.tacomaworld.com/threads/random-misfire.394448/
https://www.tacomaworld.com/threads/misfiring-issues.32191/
https://www.tacomaworld.com/threads/truck-is-running-really-bad-misfire.66211/
https://www.tacomaworld.com/threads/multiple-cylinder-misfire-codes.333593/
https://www.tacomaworld.com/threads/misfiring-loss-of-power-abnormal-engine-vibration.178120/

 

I have checked the VSV both electrically and with a vacum gauge and it appears ok.
I have swapped the plugs,injectors and coils around several times and the problem still persist.
What I am trying to understand is how some component that covers all four cylinders be responsible for a random misfire code primarily on cylinder number two.
That is why I spent so much time swapping around the coils,plugs and injectors.
I have read many hours of discussions on this topic and I think I am way past all the basics. Unless I have missed something very simple. Which can be the case. Just have to figure out what it is.

 

Will try and load a few pics of the plugs I removed. and a cop y of the box of plugs I installed. The plugs were all torqued to 13 Ft. Lb. I'm positive it's not the plugs though because I swapped them all, changed them and then swapped them around as well as the coils and injectors.
I also removed all grounds and ground them all down with a dremel tool with the sanding disc on them.
Will check the VSV again today.
Any other suggestions would be helpful.

 

While I dont know if the plugs are the sole cause of the miss fire, I do know that many people have had problems with Bosch plugs. I would run Denso/NGK and keep looking for the other causes:

https://www.tacomaworld.com/threads/random-misfire.394448/page-2

 

I had denso's in it as you can see from the photo above. I took them out after swapping them around several times and installed the Bosch's. I even swapped them around several times. In no case did any of this affect the situation. The code PO302 keeps coming back as well as the engine running rough at idle.
Am going back through and redoing some of the original test.
I just did a block test. I borrowed a tester from autozone and bought a jar of the blue fluid. The first jar of blue fluid I bought from them was watered down. Someone probably bought it, used it and then put water in it to fill it back up and returned it. Fortunately I caught it and requested another bottle.
In any case an still trying to find a solution to me problem.

 

Forgot to mention. The block test came out OK.
My two concerns about this misfire are. 98 percent of the time it comes up as a PO302, Number two cylinder. My thoughts are that it has something to do with the firing of number two coil. or number two injector firing or even the firing of number two plug. It is definitely not the plug, injector or coil them self's.
If it is something else that also covers the operation of the other three cylinders it would make me question why it only shows up as a number two cylinder misfire. If someone could explain that to me I am all ears.
If anyone has seen some specific wire that shorts out or a component that causes one of these items to misfire in providing spark or fuel please let me know.
Thank You

 

Worth a read...

https://www.yourmechanic.com/articl...-cylinder-2-misfire-detected-by-jamahl-walker

 

Thanks for the info. Never did a fuel pressure test. Will also go back and redo some of the other test. May have missed something along the way.
Am still looking for some kind of explanation as to why something that is common between all four cylinders being bad can only show up as a PO302 code.
Any thoughts?

 

Didn't see it mentioned...might try a compression/leak-down test.

 

worst case, if all those issues are present is a failing ECM? with 360k anything is possible