I had a P0333 code flare up on me recently. I disconnected the battery, changed the spark plugs, and haven’t had the issue since. Not sure if it’s exactly your fix, but it worked for me.

 

P0300 and P0333 may be totally unrelated, but more info is required. You provided only a small amount of info on several completely different issues.
1. "Spark plugs were way overdue". How overdue? 5K miles, or 50K miles?
2. What did the spark plugs look like as far as uniform deposits and insulator color? Anything unusual with the appearance of the plug from cylinder #6?
3. You stated that the engine coolant level was a GALLON low. How frequently do you check the coolant level, and what was the length of the time period when this much coolant was lost? (e.g. could have been over many months, or rather suddenly, over only a few days?)
4. During the 14 years you owned the vehicle, how many times has the engine coolant been replaced? (Anti-corrosion agents in the coolant get depleted and allow internal engine corrosion, especially at the interface of dissimilar metals like at head gaskets).

Ignition coils are unlikely to have a role in any of this ... the 1GR-FE coils are extremely reliable and rarely fail. The small amount of oil on plug from cyl #2 is typical as the spark plug tube seals age and harden - all three of them get replaced when you replace the valve cover seals.

My initial suspicion is a failing head gasket at cylinder #6, based on loss of coolant, random misfire, severe problem manifested itself at sudden high engine load, and 2007 engine at 290K miles. I'm going to guess that engine coolant has not been replaced every 100K miles?

Earlier 1GR-FE engines encounter head gasket problems (most frequently at cyl #6) at a higher rate than later engines, after design changes were made to the gasket. Gasket failure can be accelerated by not changing engine coolant at recommended intervals, leading to corrosion and leakage that sometimes shows up only under high engine load.


Does the engine ever stumble or run rough for a few seconds immediately after a cold start?
Do you ever see a slight puff of white smoke from the exhaust immediately after a cold start?
Is there a slow but continuous loss of coolant that's not visible as leakage from the water pump's weep port?
Was there an unusual amount of deposits or unusual insulator color on the spark plug removed from cyl #6?
All these are indications of a failing head gasket on cylinder bank #2.

 

Thank you both for the detailed response. I really appreciate you both.

No smoke from tail during over night cold start or during recent code episode. It doesn’t run rough hot or cold. Runs smoothly.

The ignition coil boot with oil in it was a bit cracked on the bottom. Guessing it could be from oil. One plug, I think, middle drives side was real difficult to get unscrewed.

I know this is bad, thinking back, I never touched to radiator in 290k mi. Never even opened it. Pretty amazing actually. All plugs appeared to be old but not in awful condition.

Could this be caused by an old battery? Coils? Random misfire, phantom misfire, extra stuck spark plug gasket, erg? Fuel pump?

Should I try to replicate the error by driving?

After plug change, it went 1000 mi with no issues.

Any other ideas or questions? Thank you so much for your help.

 

You didn't answer ... how many miles were on the old spark plugs?

And what did they look like as far as gap erosion and deposit buildup?

290K miles and never serviced the engine coolant?

How about periodic service of transmission fluid, transfer case and differential lubricants, and brake fluid and power steering fluid flushes?

Looks like you might want to download a copy of Toyota's Maintenance Guide for the FJC - it covers the maintenance items and inspection tasks that are to be performed every 10K miles.

It's free ... go to toyota.com, Owner's tab, Select a Vehicle, Manuals and Warranties, then finally scroll down to Warranty and Maintenance Guide.

 

Old plugs had +125k.

I didn’t check gaps on old plugs, or new ones for that matter. Like a dummy, I just installed them, confirmed it was working and discarded the old ones. Honestly I was surprised at how good the old plugs looked. I forget what type they were. Besides one plug that was hard to get out, pb blaster and warmed up the engine. Then it begrudgingly came out.

Yes I have changed transmission fluid at about 170k and rear diff. Definitely due up again. Coolant is pink in color doesn’t appear to have any oil or rust. Oil didn’t have any coolant. Frequent oil changes has been the key. New Oil and filter every 5000-7500 miles. I have the old oil filter, thinking maybe I should dissect it.

Yes definitely need to flush brakes and steering. I changed the cabin filter at 250k and omg let me tell you something, it was gross… lol

Thank you for any additional help. I am appreciative.

 

Got to thinking, Could an extremely dirty air filter cause a misfire like this? Air filter is at 30k and needs to be replaced. I am in close proximity to the Caldor fire and when taking a look at the air filter, it’s dirty. I just banged it out on the ground and there was a fair amount of dust.

Could air restriction cause problems like this? Thank you for your time spent helping me.

 

Yikes ... 125,000 miles on standard-electrode plugs?

Toyota's recommended change interval is every 30K miles.

An amazing testament to Toyota engine robustness even after exposure to prolonged 'hardship".

 

What would be your advice for next steps in chasing this problem. Thank you!

 

Honestly, @FJtest will get you through the process of diagnosing and maintaining your FJC if you've got the time and are willing to listen to him and follow his instructions.

However, given the severe lack of regular maintenance you've given the FJC, I doubt that you'll want to personally troubleshoot and correct the issues that have arisen after all these miles.

I suggest that you find a good local shop to catch up on all the recommended maintenance and get the vehicle in reliable running order.

 

I was only suggesting that a head gasket leak at cyl #6 was a possibility because of the history of early 1GR-FE engines encountering this problem, the fact that your engine started misfiring (and the flashing CEL appeared) immediately after a full-throttle engine load, the apparent loss of a gallon of coolant, and that the coolant hadn't been changed in 14 years (so the corrosion inhibitors were likely totally depleted) were all factors pointing to a possible head gasket leak.

If you never have a slight stumble immediately after a cold start, never see any white smoke in the exhaust immediately after a cold start, and never encounter any engine overheating after a prolonged period at high engine load, the potential for your problem being a head gasket leak is lessened.

The flashing CEL is a warning of a severe engine problem that may result in permanent engine damage if the engine is allowed to continue to run.

The loss of a gallon of coolant remains unexplained, and because the spark plugs (especially #6) were not closely examined for deposits and insulator color, we don't know if there is other evidence supporting the failed head gasket hypothesis.

With new plugs and apparent smooth running, I'd just verify engine oil condition (no coolant present) and coolant levels every few days, watch the coolant temperature gauge, check for pending OBD codes at the end of each day's driving to get the earliest indication of an ongoing problem, and continue to drive the vehicle, including a repeat of the full-throttle engine load that (apparently) triggered the initial 'incident'.

It's not impossible that it was just the grossly eroded plugs misfiring severely enough under load to trigger the flashing CEL.

Only additional time and miles will tell.

But get the coolant changed out ASAP, as the corrosion inhibitors are critical to protecting the thin steel head gaskets that are sandwiched between the aluminum block and heads.

 

Thank you for this response. I will flush and change out coolant this evening. Might even make a little video, see what comes out.

Is there a recommendation for best coolant?

I’m looking for some coolant that will get me another 300k miles. j/k j/k j/k

I also was thinking about my repair process with the plugs. I never did disconnect the negative battery cable to reset the idle. So maybe that had an effect on the ecu fuel trim, or something along those lines. Wife had been driving it, and can say it probably never saw over 25% throttle, until I merged on freeway at WOT.

I am very appreciative and will update when I find out more.

 

For the coolant, lubricants, spark plugs, etc. why not just follow the recommendations Toyota provides in the Owner's Manual? Copies of the Owner's Manual can be downloaded free from the same page given for the Maintenance Guide (see post #5).

The Owner's manual will recommend Toyota Extra Long Life Coolant, which Toyota recommends replacing every 100K miles. An alternative is Valvoline Zerex Asian Formula Red antifreeze, which is claimed to remain effective for 5 years or 150K miles.

Disconnecting the battery is not required when replacing the spark plugs.

Two other critical maintenance items:
1. Replace the fuel-air sensors at least every 100K miles. This is an especially critical item, as these sensors provide the feedback to the engine's ECM to properly control fuel mixture. Overall driveability, fuel consumption, throttle response, etc. are all directly affected by the fuel-air sensors.
2. Clean the Mass Airflow Sensor every 50-80K miles (assuming that you are using the stock Toyota air filter element). This sensor also provides critical data for the fuel injection system.

 

@FJtest

Sorry for non response for a while. Wife had a baby girl, running around managing the new fam dynamics.

Looks like you were correct. Drove a couple times Code began to throw P306. To me it appears that Coolant is leaking in #6

Purchased a video scope, might add its an awesome little tool, WiFi, portable, and only $25. Have my buddy Jeff send you one.

Here’s a view into Cylinder #6. Picture is after sitting for several days. I have a video and will post tonight. I believe I am experiencing a leaking/blown head gasket. Could it be a leaking injector, but no I don’t think so? I put rag over the spark plug hole wo plug in it and cranked it. Sure seems like the liquid that was ejected into rag was coolant. Probed it with wood dow, smells like coolant

#6 plug wet smelled like gas. Was brand new and has almost no miles. Car has been sitting.

Should replace head gaskets? Don’t believe the engine was ever overheated and I do believe I am catching this issue early. There doesn’t appear to be any coolant in oil or any oil in coolant. Faint white smoke on start but seems to clear. The engine is high miles but has had regular oil changes and was driven on hwy mainly. Never abused, driven mainly by cautious wife.

Does anyone a have contact with a low miles engine? I am located near Sacramento, California. I found one engine with 160k miles in it. A bit higher than I was hoping.

I have been watching this video on HG repair while on baby duty:

I think I can actually do it. Is there a gasket kit that anyone can recommend? Any other parts, I know I’ll need a 12 triple square for the head bolts.

Thoughts?

 

Your USB 'borescope camera' confirmed the presence of coolant on the piston crown ... you've got a leaking head gasket on cylinder #6. I will say that the #6 piston crown looks remarkably free of carbon for an engine with 290K miles on it, unless the leaking coolant 'steam-cleaned' that piston. It would be interesting to see a photo of a piston crown from one cylinder on Bank 1.

Since you are the original owner, you have the complete maintenance history on this engine, and know how it was driven. But, the fact that you never changed the coolant in 290K miles of ownership is a bit of a concern as far as how meticulous you were in performing preventive maintenance.

A well-maintained 1GR-FE engine can run reliably for 350 - 400K miles or more. Yours currently has 290K.

Option #1: Pull the heads (or have them pulled by a competent Toyota mechanic fully familiar with the 1GR-FE engine) and assess top end wear. Simply replacing the head gaskets should return the engine to the same state of functionality as before the head gasket leakage symptoms were first noticed.

Option #2: Locate a 'used' moderate-mileage engine and swap the current engine.

Option #3: Buy a 'rebuilt' engine from one of the larger independent rebuilders. I personally would not go this route.

 

I am going to try to replace the head gasket. Gasket sets are around $200. If I make the repair and fail, we’ll it’s only $200, then I will source a OEM low miles engine. If I succeed then I’ve saved about $3k. If I could find a low mileage engine, then I’d go that route, but the lowest I can find around Sac is 160k miles for $3400. Just too many miles IMO.

Can anyone PLEASE recommend a particular gasket set? FEL-PRO is my standard, but please let me know. I am planning on replacing radiator and waterpump. Are there other parts that any of you recommend swapping out while it is stripped? Maybe knock sensors? What do you think? Thank you so much!

 

With 290K miles on the clock, I'd replace the timing chains, the primary chain tensioner, and all the timing chain guides.

If you get the engine taken far enough apart to R&R the head gaskets and water pump, you are 80% of the way to replacing the timing chain components.

Knock sensors never fail, but timing chains inevitably wear out at some point, and 290K miles is a lot on the original chains and guides.

You will not be happy if the head gaskets restore the engine to good running condition, and 40K miles later you get crank/cam correlation fault codes from an elongated timing chain.