I've only known it to be from certain fuel additives, odd it's only on one though. Is maybe one cylinder running richer?

 

The only thing I’ve done since replacing the plugs is run a can of seafoam through the intake a couple of months back. Oddly enough, before the seafoam chug, I got a lean code along with a bad o2 sensor code back in April.

I cleared it, and until yesterday, I’ve only gotten the o2 sensor code. I confirmed that it was bad by looking at the voltage (it was nearly dead at .02v and barely fluctuating), and replaced it just yesterday. Its voltage looks good now at .3v idle and it fluctuates as expected. Could that sensor affect fuel trims on this car? It is post-catalyst.

 

Honestly I'm not sure, I don't think a post cat sensor should affect trims but I don't know exactly. One cylinder could be a little richer than the others due to a leaky injector or an injector with a dirty spray pattern. Might not hurt to run a bottle or two of Gumout Regane through it too.

 

If the O2 sensor had gone bad, since it does provide data to the ECU about how the engine is running it could have affected the tune.

Since the O2 sensor had worn out, how about the A/F sensor in front of the cat? Both of those sensors that are mounted in the exhaust live a very hard life and after 100k miles or so do begin to go off. They can continue to function way beyond that before they finally get so bad to throw a code but after about that many miles they can start sending incorrect data to the ECU for all that time.

On my cars I replace them every 100k miles and have seen mpg improve afterwards because of the above.


Of course, only use Denso sensors, from a trusted source (densoautoparts.com is a great way to find the best prices from confirmed sources).

 

Switch the plug over to another cylinder and see if #1 changes color or replace that one plug and see if it happen again just in #1.

 

I hope it’s not an injector, but I feel as if a rich mixture would look different from this. I could try to run some cleaner again, as I did run a couple of bottles of some autozone fuel system cleaner late last year, but i’ll try throwing in some regane. Thanks, Bitter!

Hello again, norm! You’re right. The A/F sensor at the front is probably gone. It is the factory sensor, and this car is at 240k cross-country miles. I’ve been thinking about changing it out, buuuuut…. this car started its life in California.

I did go with a Denso sensor for the downstream one I replaced. However, unlike that downstream, the upstream has a California emissions requirement. I don’t believe I can swap it out for a federal one without causing problems, so I’ll put that on hold and change it out some other time. When I do replace it, I hope it fixes an idling issue I’ve been trying to chase down for a while. It idles so low and rough that my headlights dim and flicker until I press on the gas, and when I get an alternator test, the machine tells me that the alternator isn’t producing enough current, despite getting a brand new alternator to try fixing this issue.

And hey CamryUS! I did swap it out with cylinder 2, so I’ll see how they look in a couple thousand miles.

 

Don't add anything to the gas during you testing time frame.

 

As mentioned above, to me it looks like fuel additive as well and probably detuned mixture too. Uneven looks I too think may be injector imbalance. But the sensors do have to be working right. Sensors, like spark plugs, are wear items too.

 

Any possibility of it being coolant? The clean cylinder top would point to this. May just be the seafoam. A pink spark plug is odd. And only on one cylinder.
Losing coolant? Compression test?

 

My first thought was a small heagasket leak steam cleaning the #1 piston. Leak down test by an experienced mechanic Would be my recommendation.

 

Yeah, I’ll replace that upstream sensor soon. If the downstream sensor went out, then surely it’s close behind. Hopefully its a slightly dirty injector at its worst.

Coolant burn did come to mind since I use pink OEM coolant in this car, but if that was the case, I don’t think it would color the plug pink. Instead, it would be a white, chalky substance coating the electrode, right? I also haven’t noticed any coolant loss since replacing my water pump back in february, and the temperature guage never goes above half. Also no smoke out the tailpipe, even on cold starts.

I haven’t done a compression test, but it seems to run perfectly fine above idle. I did, however, crank it with the ignition wires unhooked, and it sounds healthy to me.

 

The carbon coming off the piston head can be an indication of being steam cleaned. Sorry…how hard is it to pull the head in these cars? Don’t stop troubleshooting, this isn’t a closed case but seems like a small head gasket leak to me

 

you could put a new injector in... if it doesn't fix it, no harm.. and cheap.

 

Well, I was driving it around for a few hours today, when the check engine light came on again. This is the most I’ve driven it in one day since replacing the O2 sensor, so I really didn’t expect what it could be this time. I plugged in my scan tool, and lo and behold…

Oh no… I heard this code is dreaded among the Toyota community, but I don’t remember the exact details. It’s the first time it’s ever appeared on this car. Can someone enlighten me, please? 🤕🤕

 

That car used a EGR transducer, and they failed a lot. I've also encountered carbon blockage to the EGR ports. (I'm a professional with 49 years in the trade) Cleaning the carbon is a fairly difficult job on the old Previa Vans, but on yours, I'd think it to be easier.
From the photos I've seen, that car's engine is chock full of carbon.
The easiest solution, which takes time and miles, is to use premium fuel only along with changing the oil in 2000 mile intervals with Valvoline Restore and Protect. It works. Also, add a bottle of Techron to he fuel every fill up for a few moths.

But, even IF you do these things, you will have to manually clean out the EGR ports if they are stopped up.

 

Funny enough, I actually have been exclusively using Valvoline R&P with premium fuel ever since mid last year, as that’s when it started having the idling issues. It would have episodes where the engine would drop to 300rpm and rise back up constantly, and it wouldn’t respond to throttle at all. That hasn’t happened ever since; however, as I mentioned, it still idles quite rough.

Looks like i’ll have to manually clean the ports out and replace the EGR. I don’t even know where to start, though, but i’m guessing that involves completely removing the intake? To YouTube I go!

 

Yeah, Valvoline Restore and Protect is NOT meant for indefinite use. They instruct you to use it for 3 oil changes and PAY attention to the crud in the oil filter. That's difficult with a canister filter. I saved a car with 130,000 miles on it with SEVERE carbon and sludge. BUT I changed the oil and filter at 1000 miles the first time, 2000 miles the second time, and 4000 miles the final time and it REALLY made huge improvements. (2014 KIA Sorento with a 3.3L GDI engine).
After using the Valvoline, go to an oil with the Dexos1, Generation 3 denotation on the product. I recommend 5W30 for your car. Good luck!

BTW, the other well meaning folks here who tout lye and other hazardous cleaners should try Dawn Platinum! For the EGR passages) That, and Simple Green are awesome and much less lethal!

 

Oven cleaner with lye can remove carbon from parts like that (wear protection because lye eats skin, and have a plan how to keep what comes off from falling into the engine, the carbon is highly abrasive)

 

I’ll ask my mechanic about it when he does the leak test soon, there’s also another unrelated issue with the alignment that I want him to check out since it’s been absolutely killing me trying fix it. (I replaced the ENTIRE suspension myself, and after an alignment, it still pulls to the right. Brand new tires, all four wheel bearings are in perfect condition. However, it DOES have a aftermarket steering rack from years ago. Yeah, i’ll just leave this to him.) For now, I’ll keep an eye on the oil and coolant to make sure there’s no obvious signs of a blown head gasket, but both look real clean as of right now.

 

Could be the hydraulic shuttle valve in the rack is out of adjustment, if an adjustment is provided. I used to work on many 240 Volvos, and when that valve needed adjustment, the car pulled very hard. 5 minute fix was to adjust the valve.

 

A stiff stranded steel cable cut at an angle chucked in a drill makes a great EGR passage cleaning tool. Garage door cable is close to the right size but a little small. Check out wire rope at your local big box hardware store and buy a foot of it, use a small section of pipe as a guide near the head, and make sure the drill chuck is tight and DO NOT spin in the direction opposite the cables twist. The strands on the end are sharp and will fan up just a little bit while digging through the carbon. Having some compressed air to blow the crud out as you go really helps too. Good luck!

 

Your fingers are pinkish but I do not see pink on that left one but I do see gray not tan on the one on the right. I run Irridium plugs NGK or Denso . What are these?

 

Hey loneranger. It looks pink to me, and I assume everyone else also sees it. Either way, it looks quite different from the usual color I’ve seen.

You can check O2 sensor voltage using an OBDII scan tool that can see live data from the ECU assuming the wiring is good, that’s how I did it. You can also check by using a multimeter and checking the voltage at the sensor’s leads while the engine is running. The voltage should be within 0.9-0.1 volts. Any higher or lower could mean something’s wrong.

 

Hey loneranger. It looks pink to me, and I assume everyone else also sees it. Either way, it looks quite different from the usual color I’ve seen.

You can check O2 sensor voltage using an OBDII scan tool that can see live data from the ECU, assuming the wiring is good, that’s how I did it. You can also check by using a multimeter and checking the voltage at the sensor’s leads while the engine is running. The voltage should be within 0.9-0.1 volts. Any higher or lower could mean something’s wrong.

How do you check at the leads that should be plugged in right? While the engine is running being you are checking voltage with a neg/pos pins to the meter. Im confused. I do like the idea though.

 

I am also using Denso iridium’s, this is when I replaced them at the end of last year. These have the ultra fine electrode tip. I also got new wires, of course.

To check the voltages, you have to unplug the sensor. If it’s good, it should produce voltage from the exhaust gases that are blasting it. You either probe two leads, or probe one lead and touch the body of the car (ground) with the other lead. I’ve never tried this myself, though, as I have my trusty scan tool. Have you replaced both sensors? It could be a code for another one if you haven’t replaced it, since your car should have more than one.

 

I am also using Denso iridium’s, this is when I replaced them at the end of last year. These have the ultra fine electrode tip. I also got new wires, of course.

To check the voltages, you have to unplug the sensor. If it’s good, it should produce voltage from the exhaust gases that are blasting it. You either probe two leads, or probe one lead and touch the body of the car (ground) with the other lead. I’ve never tried this myself, though, as I have my trusty scan tool. Have you replaced both sensors? It could be a code for another one if you haven’t replaced it, since your car should have more than one.

You look like you have some ash deposits indicating oil consumption.

 

It could also be, on rare occasions, the wiring to the ECU.

 

All the old plugs looked that way, so it’s most likely just worn rings.

 

Now that we’re on this train of thought, could the burning of Valvoline R&P cause the plug to turn pink? 🤔 I don’t specifically remember the old plug being pink. Since this oil is so new and no one’s used it for years, could it possibly be the case if cylinder 1 is consuming more oil than the rest?

 

It could be. I'd reach out to Valvoline to ask them about that, not sure you'll get anywhere. Like I mentioned before I've only heard of red or pink plugs from fuel additives and I want to say they were some kind of octane booster either sold as an additive or added by the fuel blender. But only seeing it on one cylinder is weird, and given that's the same cylinder that burns oil, and you're using a different oil than in the past, I think your train of thought is logical here if circumstantial. So I did Google a little and the fuel additive that used to turn spark plugs red was manganese. A cursory search on Google doesn't link the two though.

 

Likely. Swap plugs around and do it the simple scientific way, see if the white plug ends up the same way.

 

Get a block tester and check for combustion gases in coolant, you can gets these as loaner tools at some of the big box stores or buy one they are not that expensive if you think its your Hgasket.

 

Tried that a couple months ago. I primed the bulb till it couldn’t suck in anymore air multiple times and the liquid stayed dark blue. I did this because I kept hearing air bubbles in the heater core, even after burping the system multiple times with a coolant funnel. This was months after I replaced the water pump because it was leaking. Turns out there were also a few hoses with small leaks, including the upper rad hose which I discovered a week ago. Somehow, there was no decrease in coolant level, though. I replaced it the same day I replaced the valve cover gasket and made this thread. However, as i’m typing this, i’m still hearing a bunch of air bubbles flowing through the heater core, even though I burped it for a good 30 minutes on that day.

 

Well, this doesn’t look good…

Some work has been done since last time. I replaced the drivers side water outlet, some hoses, OEM thermostat, flushed the coolant system, and poured fresh, OEM fruit punch right in. After a couple of weeks, I was hearing more bubbles in the heater core, and after taking off the radiator cap, I see this grey sludge forming on the rim of where the cap seals.

It feels like oil, smells like oil, tastes (no) like oil, it’s oil! Now, how do I definitively know that it’s a head gasket or the oil cooler in the radiator? As i’ve mentioned before, I’ve already tested for combustion gases, and results turned up negative.

 

Well thats oil.
Probably through the oil cooler.
Not familiar enough with the engine to know where else those two fluids could meet with each other.
Could be the head itself. An oil galley leaking into a coolant passage.
Let us know what you find.