Intermittent Misfire, Checked plugs = OK. Cleaned MAF/Throttle body, replaced PCV.

Last week I had a BAD misfire in cylinder 1 with CEL flashing. Checked plugs and they look ok (new iridiums in April) and let it sit overnight. The next day it ran better but still slight misfire and CEL turned off. Today, BAD misfire again with CEL flashing so I disconnected the battery for 5 minutes. Runs (mostly) ok now. Still has a mild rough idle.

Anyone experienced this before?

Already done:
New Plugs in April
Cleaned the throttle body and the MAF
Replaced the PCV

 

What kind of plugs did you use? The rule of thumb is don't replace quality plugs with junk plugs, or alter the electrode design. None of that Bosch quad electrode bs.

 

Have you tried swapping the coil to another cylinder and see if the misfire follows? May also need to do a compression test. That's where I would start.

 

I would suggest swapping coils after the plugs if they were not of good quality ones, if the misfires moves to the cylinder you swapped it for replace the faulty coil.

 

Thanks for the quick feedback. I used the recommended NGK iridium plugs when I changed them out.

I will try swapping the coil packs and see if the misfire jumps to another cylinder.

I think the kid who owned this truck before me used to beat on it pretty hard. I may have a burnt valve- will have to get a compression test done.

 

In short, blinking mil means misfire...

If you swap coils and the misfire persists at said cylinder, you need to do a compression test, preferably one while you run the vehicle, so you are getting dynamic compression pressures

Do not do a static compression test, which is just turning the vehicle over a couple times before reading pressures because the problem is intermittently happening while running the vehicle.

Be careful running it for too long that way because as indicated you can burn the cats up after an extended amount of ignoring the issue.

 

When you get this sorted out, I'd get rid of those iridium plugs and go back to stock. The V6 doesn't require iridium plugs and, for all I know, that might have caused the failure to begin with. Do you still have your old plugs laying around? Might be worth trying to swap in.

 

To quickly trace down a missfire on a multiple coil engine I will move around parts as suggested. Take the #1 plug and move it to cyl 2, move the #1 coil to #3. If it is the plug, then miss will move to #2, if coil it will move to #3. If it remains at #1 you could have either a compression issue as mentioned, or a faulty/clogged injector. Remember that a injector that is not injecting the proper amount or proper spray pattern can also cause a missfire.

 

I don't have the setup to do a compression test myself but I do have a good mechanic that I rely on occasionally. I will ask him to run the test for me.

As for the Cats, the truck has long tube headers on it that work as a cat-delete for the two pre-cats. I wonder if this is part of the issue- too much hot exhaust hitting the main cats??

I went with the NGK iridium plugs as I was told they were the "recommended" plug by my local parts store. Guess they just wanted to make an extra few $$'s

It is currently runs ok without the CEL flashing but I don't want to cause any damage so I am leaving it parked for a few days until I can get it to my mechanic.

 

Look, iridium plugs should never cause a misfire, unless they are worn out, and especially not NGK's as long as they were not dropped and the gap was closed on the electrode, the only advantage to them is their iridium coating on the electrode which can and will wear away if you attempt to gap them. Which is why you should never do it to them because if you did you just cost yourself the longevity they have and the reason why you bought them.

as far as a compression test goes, all you need is is a spark plug removal socket and a standard 3/8" ratchet and extension and a compression test gauge, wayyyy too simple.

I wouldn't rule injector just yet, you guys are getting a little too involved with the diagnostic process too fast, check the basics first, check the basics, and when all else fails, check the basics. Seriously...

Precats should not be a problem, all they serve is for one purpose and one purpose only... Heating up the oxygen sensors faster so the computer can go from open loop to closed loop quicker, that's it. The main cats don't care about heat to an extent as long as you are not running overly lean, hell they handle hot exhaust, fact of the matter is this, they will be happy and last a very long time as long as you maintain the 14.7/1 AF ratio which you are not at at certain points so there is an issue with one of your sensors or your engine isn't firing properly from the ignition system.

 

How do you figure checking an injector for a failure ISN'T basic? To check for problems you check the basics, spark, air, and fuel. That includes the injectors. Maybe I am misunderstanding what you are trying to get across? I have been diagnosing driveability concerns for over 20 years now, and misfires are one of the easiest to trace the fault.

 

I made sure NOT to gap the plugs when I put them in for that very reason. So I don't think they are the issue here.

I will look for a compression gauge - any easy to follow instructions on how to use one? And what lbs range am I looking for?

I haven't had to check/replace an injector before. Anyone have a link to a good walkthrough?

"as long as you maintain the 14.7/1 AF ratio which you are not at at certain points so there is an issue with one of your sensors " --- which sensor would that be 12TRDTacoma?

 

Bamatoy97 I agree they are easy to trace, though I don't check fuel until I check all of the possible spark potentials first. It's easier to access spark then it is fuel, not to mention unless the car is real old (which this one is not) the problem typically stems from a misfire within the ignition system before it has a problem within the fuel delivery system. Then again he never stated mileage on this car, so maybe we should had started with that before throwing out shots in the dark.

Nofinishline, I wouldn't worry about a sensor just yet until you rule the basics out first. Spark/fuel/air. If those are fine there is one thing I didn't ask, how many miles are on this car???

As far as compression goes if you see a variance of over 25psi between cylinders (it's been a while since I did this) then you might want to dig deeper into that cylinder, but typically when I do compression tests I see anything from 150-200 psi from the test on every cylinder when it's in good shape, don't forget you have to factor in the fact that there will be some leak down due to piston rings allowing some pressure to escape.

 

Hey guys. Yeah I forgot to state mileage, etc.
'06 Access cab, 1GR FE motor with 77k on it.
With that low of mileage, I can't imagine an injector going bad.

 

You never know. I fixed a 2000 Celica with only 100k on it with 4 bad injectors.

Being that you have a V6 and the injectors are a pain to get to, that would be the last place I would test.

 

Over the years I have done this job, I have seen injectors fail at less than 5k miles on a vehicle. It happens. parts fail all the time on every year, make, and model. On average I would say when it comes to misfires, I average almost 50-50 between spark and fuel related misfires. Of course a few have been compression issues, but rarely have I seen them come in for a misfire code and be compression related. USUALLY when compression is an issue, it comes in on the hook with a broken spring or valve...lol.

 

Exactly. I love broken timing belts.

BTW I can't stop staring at your sig, you gotta stop that thing!!!!

 

Nope, not gonna happen! hahaha

 

Yeah x2, I LOVE that sig! That pic needs to stop moving because I'm just jaw dropped at what I am seeing. Boing boing boing!!!!

I haven't really every seen injectors be a problem on a vehicle namely so a toyota, but then again I've only been doing this for about 10 years...

I will agree however 50-50 fuel and spark, occasionally you have the air leak after a MAF or something going on with actual intake of air..

If the injectors are really an issue to get to on these engines, I would DEFINITELY start with the ignition system first.