P0306 Question - please help

[dodgers1970]

So, on my 2004 4Runner V6, I got the Check Engine Light, I got the VSC codes (mentioned this in a separate post). I was getting a rough idle at start-up, especially when cold (in mornings).

I got the P0306 code. The dealer said it was a head gasket since they changed positions of the number 6 coil and still got the misfire.

I took it to a private mechanic. The private mechanic replaced the MAF (Mass Air Flow) Sensor, the Air Filter, and the PCV Valve.

He did the same coil swapping test and found the same P0306 code. After the MAF Sensor, it seemed better. He reset Check Engine Light and sent me on my way.

Two mornings later, the Check Engine Light, and VSC Lights came back on. I found a coupon from Precision Tune for a Free Check Engine Light Diagnosis - and told them nothing about what the dealer said, nor did I tell them of any work the other mechanic did.

After an hour, the mechanic comes out and tells me, "As part of our check engine light diagnoses, I check the plugs, the coil, the injectors, and I do a thorough compression check. Your injectors are clicking and working well. The coil tested fine. The compression is as good in # 6 as it is in the other 5 cylinders. Everything looks good, but let me show you this. A few of your plugs have hairline fractures in the porcelein. I suggest changing those. When they swapped the plug positions when the swapped the coil positions, I guess a few were fouling potentially and causing the misfire in 6. I eliminated the possibility of head gasket issues." I interrupted and asked, "How did you arrive at that?" and he replied, "You're not overheating, there is no coolant smell out of the heater vents when I test drove it. Your Toyota coolant is at the full mark in your overflow tank, with no signs of it seeping out, but most importantly, no loss of compression whatsoever. I eliminated the possibilty of the Fuel Pressure Sending Unit because that would show a miscellaneous P0300 code, not a specific one...."

So he puts in NGK IRIDIUM Spark Plugs. He cleaned the throttle body and plate. The car was near empty, so I added a Chevron Techron Fuel Injector/Fuel System Cleaner Additive, filled the tank with Chevron Super Unleaded gas.

Ran beautifully for the day. In fact, when idling at a stoplight, man, it was like a new car...as though I were sitting on a couch. HOWEVER, went to start it after a few hours of not running it. So starting it when cold, I got the rough idle (sigh)...No check engine light ...YET... But the rough idle...

So after that LONG description, my questions are:

1. Could something be causing the coil to fail?
2. Could the coil actually be failing regardless of this test?
3. I heard the oxygen sensors cannot be responsible for this. Toyota told me this was a common misdiagnosis for a P306. Is that true?
4. Could it actually be the head gasket with no loss in compression?
5. Does it make sense to try changing the coil for the hell of it? $200 is a lot less than $4,800.00.

My issue was initially the $4800 they want to replace the head gasket. In fact, no one else in San Jose really wants to take on the job! I'm getting responses like "Man, I'm swamped and that's a 22 hour job!" Most people are telling me to buy a new engine.

My issue has become: "If I replace the head gasket and it doesn't solve the issue, then what?!"

Anyone have any thoughts?? Any ideas? Thanks!

 

[Chef-j]

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[Chef-j]

If they swapped coils around and misfire code stays at #6, its not coil pack.
Sounds either wire or headgasket to me.(since they already tried plugs and coil)

Wait and see if u get a code again.

Oh, 5k for replace headgasket is bs.

 

[dodgers1970]

Are there spark plug wires on a 2004?? I, for some reason, thought 2002 and newer didn't have traditional wires

 

[dodgers1970]

well, it appears that if it's a head gasket issue, with no loss in compression, the Toyota 4Runner is not really the reliable car people think it is. Sure I have a lot of miles, but this isn't routine maintenance like a water pump... It's a major engine overhaul. Everyone estimates it at 21 hours. The lowest cost I could find was $3295.00.

 

[Chef-j]

Oxygen sensors can cause misfire, but i do believe they will throw oxygen code as well, not just misfire @ #cyl.

I was point out wire harness that connect to coil pack, but i thought about it again...if it is it should throw other cyl misfire as well.

It is really hard to point out which causing a proble without really looking at it. Sounds like your coil works fine and plugs are new.

Did it throw any code yet? Did the last shop reset ECU before you leave the shop?

Oh btw, don't give up man it could be something simple issue.

 

[dodgers1970]

Hi..only the P0306 Code... dealer reset it, mechanic reset it... it keeps coming back on...

Replaced plugs, pcv valve, MAF Sensor, cleaned fuel injectors, throttle body, throttle plate, etc.

 

[Chef-j]

Maybe this can help you little bit.
Answers.com - What are the signs of a blown head gasket

Pm sent.

 

[3TonMike]

I wouldn't jump on those head gaskets just yet. When exactly will it do it? Does it only do it once in the morning after sitting over night. Will it occur if you drive it around the block and let it sit for a few hrs, when you restart it?

 

[dodgers1970]

Hi Mike:

Here's the snapshot of what's going on and what I've done so far. I appreciate the help, by the way.

OK, so one morning, I started my car. I rumbled roughly when I first started it, I backed out of my driveway, and it was gone. The Check Engine Light and VSC OFF/VSC TRAC codes came on.

I knew this sometimes means a loose gas cap. I pulled over, checked the gas cap, it was fine. Since the Toyota dealer was close, I drive straight there, hoping it was an easy fix. They got a P0306 code. They said "Your plugs look good, and clean, and I don't see any fluid leaking, or missing from your overflow tank, so I wouldn't worry," the mechanic explained.

They took it in, swapped the coil position and the plug position. They kept it overnight. They said the next morning, they still got a P0306 code.

The service advisor said, "The injector seems to be working, so we looked in the engine with a Borescope and found coolant." I argued, "No overheating, no loss in compression, so white smoke, no smells, Coolant overflow is at the FULL line. Doesn't sound like a Head Gasket."

The dealer has done THREE shady things to me. I went back because it's 2-3 blocks from my house, and I am smart enough to not fall for things. They reset the Engine lights for me.

I took my car back and went to a different mechanic for a 2nd opinion. They said "We found a hairline fracture in your plugs. We should get those changed." Here's everything we did so far at the 2nd Mechanic:

[*]Changed Air Filter
[*]Changed Mass Air Flow Sensor
[*]Cleaned Throttle Body/Throttle plate
[*]Replaced Pcv Valve
[*]Tested Fuel Injector
[*]Did Fuel Injection Service
[*]Changed Oil
[*]Change Spark Plugs to NGK Iridium Plugs
[*]Re-tested Coil
[*]Removed Manifold to look for loose hoses, wires, see what could be going on

The tank was near empty, so I added a Chevron Techron Gas Additive that cleans fuel injectors and fuel system. Filled tank with Super Unleaded.

Car ran great for a full day. The next morning, got the misfire symptons. Rumble/Rough Idle at the start-up, etc.

I called a shop that specializes in Engine repair, has a machine shop onsite, and specializes in Foreign cars. Sign says "Toyota, Lexus, Acura, Honda, Infiniti, etc." - They explained, "It sounds like it could be a head gasket leak. A blown head gasket has the symptons you're thinking of with the smoke and overheating, etc. A leaking head gasket may not show those symptoms, but when you first turn on your car, a little coolant may hit the plug because it's being sent there for the first time, fouling the # 6 plug, giving you your symptoms. As the car warms and everything mixes, it's no longer hitting your plug and the symptoms vanish." They quoted me 1/3 of what the dealer quoted me. They explained that they were less costly because they have a machine shop on site, can do that themselves, and because they charge so much less per hour than Toyota does. They also explained that Toyota tacks on extra hours of time. Meaning, they say this takes 16 hours, Toyota estimated 22.

Last thing I will mention as to why I didn't trust Toyota.

Episode 1:

Brakes squeaked, took in for brake job. They said I needed rotors. I paid for brand new rotors and brake pads. Three MONTHS later, rotors were shot. They replaced the rotors under warranty. I wondered "Did they replace them in the first place?!"
A little less than a year later, maybe 8-10 months, rotors were shot again. I learned that when they replaced them under warranty, they left the OLD, unevenly worn pads on!!!

Episode 2:

They told me during an oil change that they inspected the vehicle and I desparately needed a water pump because of the pink gook around the edges. I took it elsewhere, it was pressure tested and the mechanic explained, "That pink is simply gasket sealant. It would be leaking water if it were bad and this water pump is completely fine."

Episode 3:

They told me at a different oil change, "You have nearly 120,000 miles. You immediately need to change your timing belt." I was skeptical, but called to have it changed at ANOTHER Toyota Dealership closer to work. They explained, "Sir, you have a timing CHAIN on your vehicle, not a belt."

So why did I go back? A - I've never fallen for it, and B - it was 3 blocks from the house.

 

[Chef-j]

Sounds like you found a shop to fix it for you! and sounds great price? :thumb3:

 

[CJ3Flyr]

Glad you found a good indi shop to treat you fairly.


You are only 3rd or 4th 4.0L headgasket in the 4Runner I know of. Overall it's a great but alas, not perfect engine. I hate it for you that you have to go through this.


I'd be very interested hear any speculation as to the "why" this shop has to offer even if it's just an educated guess.
:cheers:

 

[3TonMike]

A little about myself. I spent the last decade on the domestic side of auto repair. I was a dealer tech for one of the big 3. I specialized in driveability, engine and diesel repair. Trust me. I know the games dealers play. Some day ill write a memoir, on some of the things i saw firsthand. Anyway I left that behind to pursuit a more transparent career with integrity. So here i am giving back.
It sounds like you found a good shop. I have seen a head gasket do exactly what your describing. Though its very uncommon. The last engine that had what your concern. Had a casting flaw that went from the coolant passage to the cyl wall. So as the engine cooled overnight a little coolant would seep in to the cyl, and misfire on start up. Once the engine was warm the thermal expansion of the cylinder wall would seal the crack. I hope its not something that serious. It does sound like your guys are on the right path though. While I'm not a Toyota expert, iv paid my dues on cars. Feel free to ask if any one needs advice.

 

[dodgers1970]

update

The shop is telling me, "we've run it through several tests, compression, leak, others, and we cannot find anything wrong with the heads/head gasket... you shouldn't replace it.

Sigh... now what?

 

[3TonMike]

The shop is telling me, "we've run it through several tests, compression, leak, others, and we cannot find anything wrong with the heads/head gasket... you shouldn't replace it.

Sigh... now what?

Some stuff to try
Least evasive. Let it sit over night, pull the #6 spark plug. tightly roll up a paper towel. Insert thought the spark plug hole and swab around in the top of the piston. It sounds cheesy but if theres a good amount of liquid the paper towel will wick it up. A good smell, touch, taste may give a direction. The tip of the paper towel should slightly turn dark, and a light oil smell may be present.

I have been burned by a new plug out of the box, it could be bad.

Warm to operating temp, un bolt the fuel rail lift up not disturbing the fuel rail injector relationship. Only lift the rail enough to slip 6 shot glasses under the injector tips that goes into the manifold. let sit over night. In the am if the injectors have leaked you'll have fuel sitting in the failed injectors shot glass.

Warm to operating temp. Disconnect the coil connection attach a noid light to coil. Let set over night, have some one start it , while you watch the noild light for pulses. No pulses could be a bad coil driver in the pcm

Run the same test as above except on the connector on the injector.

Fuel pressure test over night. Attach a fuel pressure Gage on the fuel rail. let set overnight. Crank in the am and see what the fuel pressure does. It may be losing its prime, and the enging may be starting before the fuel pressure has fully built, in the fuel rail.

It also could be a miss on the companion cyl. Due to the nature of balance, and timing 2 pistons are always at top dead center at once. One will be finishing the exhaust stroke, the other on the start of power stroke. Some thing could be causing the pcm to miss flag the cyl. Off the top of my head i do not know the firing order of the v6 4runner, but here is a method the should determin the paird cyl. Take the firing order and cut in in half, giving you to sets of 3. the first numbers are paired, the seconds are paired, the 3 are paired. Ie 1 2 3 4 5 6 the paired cyls are 1 and 4, 2 and 5, 3 and 6. The culprit could be a bad coil or injector on the companion cyl. Which would mean, every one is looking a the wrong cyl.

Id check to see if the fuel pressure is bleeding down (losing prime) overnight. My spider senses tingle on that one.

 

[eskimochaos]

Glad you found a good indi shop to treat you fairly.


You are only 3rd or 4th 4.0L headgasket in the 4Runner I know of. Overall it's a great but alas, not perfect engine. I hate it for you that you have to go through this.


I'd be very interested hear any speculation as to the "why" this shop has to offer even if it's just an educated guess.
:cheers:

That's a lot considering it debuted in 03.....

 

[dodgers1970]

P0306 head gasket

Well, Toyota said it's the head gasket due to a Borescope test. I hate dealers and feel that they lie, so I was skeptical.

However, after 2 weeks of the rough idling, and no check engine light, I have noticed the coolant from the Coolant OVerflow tank... it went from FULL Line to only about 25% left. Now, no smoke, no overheating, but it's leaking somewhere. I don't see any on the ground, so I am thinking it really is the head gasket... any thoughts?

 

[grosse14]

Well, Toyota said it's the head gasket due to a Borescope test. I hate dealers and feel that they lie, so I was skeptical.

However, after 2 weeks of the rough idling, and no check engine light, I have noticed the coolant from the Coolant OVerflow tank... it went from FULL Line to only about 25% left. Now, no smoke, no overheating, but it's leaking somewhere. I don't see any on the ground, so I am thinking it really is the head gasket... any thoughts?

I have 2004 with 140,000 with the CEL coming on for the last 6-9 months or so. I checked with the dealer and they suggested fuel injector cleaning, but that didn't help. I also have some intermittent rough idle when I start it about 5-10 seconds. The dealer has suggested gasket and inspection of valves (Actually he suggested a new truck stating he wouldn’t pay $3k on a truck that might be $10K at best). While I’ve always suspected the gasket, I’ve been unwilling pay for a repair of that magnitude without more than a guess. I’m also fearful that it might not be a gasket but a cracked block which would be a huge waste to replace the gasket.
I plan on investigating the possibility of an O2 sensor, then have a compression check. I’m still looking for missing coolant as confirmation. Please keep the posts coming, as I’m very interested in what fixes your problems.may

 

[progress4m]

That sucks to see more head gasket issues… here is another recent post: http://www.toyota-4runner.org/4th-gen-t4rs/73706-2004-limited-edition-4runner-4x4-head-gasket.html

 

[Griff 05]

I realize this is an older thread, so hopefully I'll get lucky with some input:

I recently changed the spark plugs in my 05 v8, as well as my oil. I performed the sea foam system into the manifold, gas and oil. I drove the car a week and a half or so later and got the check engine light. Did a diagnostic, and the engine is misfiring in 7 and 8. I put new coil plugs on, still misfiring in 7 and 8. Switched plugs 5 and 7, still misfiring. Could this be a head gasket issue? Why would that occur just by changing my plugs at 76k miles? There were no issues prior to changing the plugs. I'm using Bosch iridium plugs. Thoughts?