2004 Toyota 4Runner P0306 Misfire Diagnosis 

I have the exact problem. This is the only video I’ve found that goes in-depth about misfire. There’s hundreds of videos about misfires and all they show is plugs and coils. Everyone knows to check that. I’ve spent around $2000 already trying to fix my truck. I can’t thank you enough. I’m confident this is my problem. My truck is doing exactly the same thing as this one.

The forth pin on a ignition coil is usually a feed back signal and is used by the ecu to monitor the performance activity of the coil when firing typically pins are as follows 1 Positive supply - switched battery voltage. 2 Trigger - typically a 5 V active-high pulse from the ECM to the coil. 3 Feedback - typically a 5 V active-low pulse from the coil to the ECM. 4Ground/Earth - battery negative.

Reminds me of a 98 Ford F150 that I got rid of. It had the same symptoms of misfires, very little coolant loss without any visible leaks. One of the sparkplug tubes had coolant in it. After removing the intake, I found that the intake gasket had 2 cracks between the coolant port and that one cylinder with the coolant in it. Great investigative work!

Nice product placement Matt. :) Before I forget, have a great Thanksgiving! I've enjoyed your content over the years because your good at explaining the thought process of your approach. I think that's as important as the actual fix itself.

Great video, I work at a used car lot. We get a lot of trade ins most of the time they have some sort of what seems like a major engine repair "rebuild or replace" needed. More often than not it's some sort of cylinder killing issue. Stuck lifter, bend pushrod or broken valve springs. Point being we dive deep and perform a complete diagnosis. Knowing exactly what failed and being able to prove it is the only acceptable diagnosis our service guy accepts.

Happy Thanksgiving Matt! Great to see you back!

Great channel. I love the scientific approach. Right now I'm a10%er, striving for 2%!

Nice job explaining everything. Happy Thanksgiving!

Matt, thanks for the video.Always waiting on you men.You be like best.

Happy Thanksgiving, Matt! Another great video.

I used to watch Matt a few years ago.... kinda went away for a while.. now I am back for the excellent sarcasm!

Another good video, and solid diagnostic approach. Been a long time fan of your channel. Quick tip I've seen on engines with coolant that gets into the cylinder. Pull the plug and use a video scope, or just look down through the plug hole. If it's a lot cleaner than the other cylinders, that's an indication it's likely burning coolant. Basically, as it burns it off, it's steam cleaning the cylinder, and it'll be noticeably cleaner.

Another great video, It has given me motivation to get back on my project vehicle, a 1988 Ford F 250 diesel. It has an issue with glow plugs not firing from the relay I think. Work has gotten me so bogged down its been on my "back burner". You make me want to re-focus and get it done! When my wife yells at me for being under the hood of that truck on Thanksgiving day, I'm going to tell her its your fault! LOL! Happy Thanksgiving to you and your family.

Matt, thanks for another excellent video! Love the SBQM channel too. BTW, you could also hold a piece of white paper over the cylinder while cranking...this will allow you to see the coolant (or fuel, or oil) on the paper for further verification.

Nice ! Matt, hope you and the Mrs. Have a Happy Thanksgiving ! Take Care !

There is a handy smoke machine accessory that goes in the intake tube with an inflatable bladder with a tube that passes through so you can hook the smoke machine to. Nice video, Matt.

I continue the work today with the miss on number 3 cylinder on the Toyota and found a fuel injector leaking very little . I did the test with a fuel injector cleaner putting pressure on the fuel real and all 6 injectors and blocking the return and found a very small leak removed The spark plug and found gas on the cylinder #3 . The miss got fixed after letting the truck with out running for 10 minutes , I did this 3times to make sure it was fixed. Thank you again for all your teaching Matt

Another Great vídeo Matt I like seeing again, a bit hug. 👏🔧👌

Happy Thanksgiving Schrodingers!

Happy Thanksgiving, Matt and Vicki!! 🇺🇸🙏

Being quite familiar with Toyotas I can tell that a careful reading of the plugs will show the smallest coolant leak in a cylinder if you know what you’re looking for. Head gasket issues are an age old issue with the 3.4 and the 3.0 that preceded it.

Good job! Great video!!

Nice work as usual. My guess is the garage she took it to might have seen that the spark plug on number 6 was clean and guessed head gasket failure from the coolant jacket but a chemical test or a relative/compression test would have ruled that out in 10 minutes. You know my Toyota turd wagon has those 4 pin coils but only has 3 wires in use on them. I always wondered what the 4th pin was for on them as 3 wires gives you 12V, ground and the trigger signal from the engine ECU.

Thank you sir to shares your experience

Its always a good day when Schrodinger's Box posts another video!

I was wondering when we would get a new video. I'm studying under you. Class is in session. I will rewatch in the a.m. I'm not firing on all cylinders this time of night. Thanks for the instruction.

Matt, Thanks for the video. I have one of these that uses a very small amount of coolant. Mine still runs good, never had the “miss when cold” issue. There is a widespread belief on the forums that there is some factory defect on head gaskets from 04 and 05. Makes me wonder if many of the HG failure diagnosis are intake gasket leaks instead. Interesting that they almost always say it’s cyl #6.

Happy Thanksgiving from Down Under...

I work on a lot of these engines, but I don't remember coolant running through the intake plenum. I could be wrong though. It has been a while since I have had the lower intake off, so I can have a couple engines mixed up, but I thought that it had a pipe running under the intake from the front to the back of the engine, down in the valley between the cylinder heads. Also, I have seen a lot of these head gaskets fail, and I love scopes more than the next guy, but I have never seen the head gasket on THIS engine leak so badly that it caused low compression, especially a bad relative compression test. When I check the head gasket, id rather put 100 psi in the cylinder, and watch for coolant leaking into the radiator. Your smoke machine probably only puts out 2-3 psi? I'm not sure that was enough pressure to cause the leak to present itself. I'm not saying that it has a bad head gasket. That's just how I would check it myself. I have been starting to get into pulse testing, or pressure differential testing, using a piezo element on the radiator to watch for pressure spikes while cranking the engine, and I have had good luck that way as well, since you already had the scope out to do the RC test. As far as the ignition coil. It has a 12v power supply, constant, and a ground. The ecm sends 5v to a transistor to turn the coil on. The ECM also sends 5V from the ECM that the coil pulls down to ground when the coil fires to confirm that it did fire to the ECM. But good video! I am going to dig into service info a little more to verify which toyota engine has the coolant in the intake, and which one doesn't.

Happy Thanksgiving Matt,nice to see you!

Good video. Was the noise eminating from the spark plug hole or the intake manifold?

As a avid Toyota fan I can say it definitely is a coolant leak in cylinder 6. Coolant will leak down after the engine is shutdown. Causing misfire upon startup. I own a 2005 with the 1gr-fe with 250,000 miles and have had the same erratic code for 12 years. Besides a bit of coolant over time, no other issues. The head gasket part number did change after 2006. So maybe Toyota figured it out. Regardless, I’ve had nothing but great experiences with Toyota.

Yes another video!

New guy "on the block" lol I'd still check for fuel pressure drop just to eliminate the possibility... but I'm still curious on the repair. And Happy Thanksgiving and Happy Holidays in general!

Few years ago i fixed a misfire in my brother's car that was caused by a coolant leak on a spark wire from a cracked coolant passage in the intake manifold, my first thought was that the water drops from the windshield. The car was 1997 mercury grand marquise.

Great to see another video from SB! I am not familiar with the design of the Toyota engine. The compression test was good so the leak must be really tiny. Wouldn't the coolant leak be coming through a portion of the head gasket?

Informative and funny, this wrap should keep the air filter fresher hahahaha

I have the same issue miss fire only cold start on my 4runner. What did you do fix it? Please let me know thanks

Sorry i don't speak english very well, so you speack so quick in your video😭😭😭. Thank you for this knowledge.🙏🙏🙏 I want to know by witch way coolant can go inside the cylinder 6? You did the compression test it was ok. Or it going by leak intake manifold ?

Good job

I really want to try out. I missed the last time because my crap car broke. Can I still try again?

Had a misfire on my 2004 4Runner during first 30 seconds of a cold start and was not losing coolant. Engine light, VSN, and one more light I can't remember now was on. Sometimes a flashing engine light. Pulled and inspected the spark plugs to find oil covering one plug. Replaced those gaskets involved and no misfire.

So was the head gasket the issue with this truck? I’m having the same problem with my 05’ Tacoma

All I could figure is the pressure in the upper intake I pulled a vacuum line while the manifold was completely out of the vehicle and it released vacume is that normal?

Great info thinks

Thanks Matt. Happy Thanksgiving.

"I hope I get an iron for Christmas." LMAO

Any chance of a conclusive follow up please Matt? We heard the gurgle gurgling...and we know the coolant was getting into the cylinder from somewhere...but still a little unlclear where the gurgle was gurgling from?

Nicely done. I’m not familiar with this engine, But how does the coolant find its way to intake manifold?

I am working on one exactly the Same with a miss on number 3 cylinder , I can not find The problem , I did not know the coolant runs. Through intake manifold When said You intake manifold you mean the lower intake manifold. I will check the coolant system tomorrow thank you

Seconding the part where you said the early 2000s Chevy cars had this problem. My 3.5 Malibu did exactly what happened here.

They're the jobs that separate the men from the boys. Good shit bro!

Ive had to replace several knock sensor wire harness on these engines due to rodents. They sit under the lower intake. There is no coolant passage there. There is a coolant pipe that runs from the back of both cylinder heads to the front thermostat housing. Also have had this issue of coolant entering #6 cylinder. Let it sitt for a few hours after warm up and could see the coolant leaking into the cylinder between the head and block with a borescope. I could see the droplets.worth giving it a try. I own a tacoma with the same engine and hope mine does not fail.

Very helpful! How did you attach a compressor hose to the radiator? One thing I'm not sure about (and this is a dumb question) but is this be a head gasket or an intake gasket problem?

So what’s the procedure to fix this problem? change the head gasket?

It would be interesting to see the original plugs. Maybe the number six plug looked cleaner than the others.

Hello Master Thank you for these helpful videos. Sorry to address my issue and ask you in a comment. I am from Lebanon so there is no other way. I have a chevy captiva 2009. And I'm experiencing misfire in c3 only on acceleration. Any ideas Can you help me plz

I guess after watching this video I'm still confused as to what the solution would be to fix the problem. I am having the same issue. So is it a head gasket problem or not?

So was it a head gasket after all?? I missed the final conclusion! Thanks mine is doing the same thing when cold.

I put transmission in a year ago and now it's down shifting in 2nd gear and when it shifts on out it's right back down shifting again it just started this all of a sudden is there anything you can tell me to do? D.J.

Cool shirt👍

Matt, just a question, does this car not use red coolant? As per the clear reservoir behind the radiator? Will pouring green coolant in a car that uses red coolant do any damage at all? (Or anyone else?)

Did use use volts measuring for the relative compression test ? I thought you would have used an ampere measurement.

Watch your videos couple times as diagnostic tech. I hate to see you possibly miss a common thing I see with this engine. Could you boroscope the cylinder to confirm source of leak. Not sure how the other mechanic narrowed it down, boroscope helps narrows it. Keep up the great videos.

So what is causing coolant to leak into the cylinder if its not the head gasket, how would you fix this problem?

It feels like this diagnosis needs to go a little further to clarify how coolant is making its way into the cylinder, even though I do understand why the customer may want to cut her losses. She may get another year if she decides to ride the horse til it dies, but that decision assumes there is no quick intake manifold fix. Any test will have false negatives, and false negative dye tests for combustion products in the cooling system are pretty common. If coolant is truly leaking into the intake manifold, isn't there a chance of fixing it by chasing down where you heard it leaking? Are you thinking that, after all, it actually is an early head gasket failure, leaking coolant but not losing compression yet?

But Matt, I'm confused. Isn't one reason for coolant in the cylinder a blown head gasket?? How else is it getting in there?

Can you explain how the coolant would be leaking from the intake manifold gasket into the #6 cylinder when there are no coolant passages from the cylinder head into the intake manifold at all. Just curious.

From the point of view of the garage that "misdiagnosed" Many shops will replace plugs as a matter of course before even looking for the problem. This was more of an old school approach from the breaker point and carburetor days.It sounds like they probably did find water in the cylinder, however they do not really have the potential to make very much money out of an intake manifold gasket job. Whereas a head job involves only a little more time from their point of view and they can make money on the outsourcing of the machine shop work (even if its not actually required they are likely to have a policy of machining every head), they will also be doing the timing belt so they will add the timing belt job to the bill. During the repair they would have found the manifold leak or they would have replaced the seals at any rate to it would never be proved that it was not the head gasket.Anyway by the time a car is 15 years old a general top end rebuild is not actually a bad thing to do for the customer in the long term.In a way how is this different from what most shops do with a sticking brake caliper. They replace the caliper and charge a few hundred when maybe they could have replaced 5 dollar square seal in 15 minutes?All this is why I fix my own cars. I can usually work out exactly what part to replace with techniques I learnt form channels like this.

So what did we determine it is lower intake manifold?

great to see you back, Bernie as to the "elephant in your pantz" ... check with yer boyfriends

Where are you located I’m having the same exact problems with my 2005 4Runner 4.0l 2wd

I noticed you mixed coolant colors. There is some controversy over mixing colors, whats your professional opinion on this?

interesting one... if it were me i'm not sure i'd bother changing that out until it became more than a minor inconvenience lol

What did you do to fix the coolant going in to the cylinder ? Tks

I am having this same problem. P0306 code. Flushed the injectors, swapped coils and plugs and still the same code arise. Where exactly do the intake manifold have coolant run through?

Hello, can I work with you and send you some professional car diagnostic scanners? Seriously, your video is really awesome, I hope to have the opportunity to work with you.😀

GOLD!

Hello sir any idea what’s the best products to clean your Engine? Thank you

So what's the fix for that? A new gasket set or a new intake manifold to go with the new gasket set?

So what is the fix?? I have an ‘04 just like that with the exact same issue. Thanks

When you make the relative compressions test with the scope. Do you measure voltage drop or amp? What are the best method from you Perspektive voltage or amp.

I have been working on toyota's and honda's and nissans for over 40 + years and I can tell you that is deffinatly a head gasket. I don't want you to call me an ASS HAT but cast iron blocks with alluminum heads is a common problem, those chemical testers are not reliable. Even american cars that went that route in the 80's and 90's had the same problem, they leak coolant over night it blows out in the morning and your good to go, do it enough then car runs low on coolant and it over heats, look at that, the car had a head gasket problem first before it over heated, amagine that! As for your coil one is power, one is ground, one is an IGT wire witch is a 5 volt square wave to the coil to fire it and the last is the IGF wire witch is 5 volt square wave from the coil back to the computer that tells the computer that the coil fired. As for customers that think they know what's going on with there cars, they don't , trust your own instincts.

How can you tell the coolant isn't leaking due to a breach in the head gasket between a coolant passage and the cylinder?

Does the intake manifold on this Toyota has a coolant passage,

so was it a blown head gasket or cracked head?

So how do you fix that coolant leak into the intake? I believe I have the same problem.

only time you should change something just because is oil seals, oil and oil filter and thats only if you've checked the oil and filter to make sure there's no chunks and only if you've got half the engine or gearbox apart already and it doesn't make sense not to change the oil seal

So the original shop was correct about head gasket issue in the end?

What happens on these is when the engine is at operating temperature and shut off for hours, coolant will pool onto the top of the piston from a breach in the head gasket. It's common on these Toyota 4.0l engines and it's always #6 cylinder that misfires.

Is that a Blue Point speed wrench on the clothing?

Just had this problem multi cylinder misfires as well as individual cylinders lower and uppers replaced cleaned it all up put it back #6 still swapped coils injectors nothing I'm lost

The coil terminals should be 1-constant + 2-constant- 3-trigger 4-diagnostic/data signal

So what would be the fix if you said it did not need a new head gasket?

What would your recommendations for a code p0104 and p0102 on a 97 Nissan pathfinder 3.3L

First good video and the way to think and applying the logic. Sorry for asking. I was checking the design. That engine is not have coolant passage thru the intake like 3400 GM. That make's me think is a blown head gasket. Because is not any other way the water can get to cylinder 6 by design. I was in the same steps for the diag. But I didn't get clear how water is making it to the cylinder if the chance of blow head gasket is out the equation?

How did you disable the fuel injectors without taking the intake off?

What about a leaking fuel injector on #6 it could be a little rich and burns it out before it goes to close loop

I have same problem in my Toyota 4 runner 2006 how to fix that please reply

Couldn’t have you measured engine vacuum with a vacuum gauge at startup as a baseline measurement?