Burnt Valve?

I have a 2019 with 10000 miles doing the same thing. In the 1970’s I had a shop in Gainesville Fl. When we saw a Toyota come in we knew we had a valve job. What I found was, the exhaust stem was expanding from the exhaust heat (1300+ degrees) causing the valve to stick before it would close completely. We would under cut the stem just above the head so any expansion right at the guide entrance didn’t make the valve stick. Problem solved. The Toyota rep for the area let Toyota know what I was doing and Toyota started to do it to the 1800 engines. The Rep gave me a bunch of take off heads for the tip. I think we have this happening again. They are running too lean, thus the ruff running and poor idle. This will also bring the exhaust temp up. Any one that flys an airplane knows what happens when you reach peak exhaust temp, ruff running, so you richer it up 25 degrees. On an engine with fuel injection we can run lean of peak 25 to 50 degrees before ruff happens, IF, you have the same head temps in each cyl. Thus the problem with the same cylinder in several Tacoma engines. By the way my 2019 Tacoma has not produced a code. The dealer sold me this Tacoma knowing it had a recall fo the fuel pump and no cure yet.

 

Pic of the undercut on the stem please?

 

few will take down a relatively new head

true engines are running lean ...........leaner

seldom do ALL cylinders fire/run the same thru out a normal operating range

25degrees seems a very narrow margin

not sure of rep's explanation

 

I build engines for SCCA racers and any of my engines will have less than 10 degrees difference. My airplane engines will be about 5 degrees from lowest to highest temp. If the manifolds and ports are flow matched they should be very close to the same. An imperfection in the primary induction tubes of about 1/8th of an inch in diameter, like a weld end, will make a 30 cubic feet per minute difference in an inch and 1/4 tube. When you are talking about lean mixture where you are on verge of something burning a piston, valve or top rings the temps better be close. As I said, people who fly airplanes know this and what it feels like. I am only offering you my theory of what is happening. I know the lean feel and what the instruments read. Under some conditions the exhaust temps will reach 1600 degrees. Normally the best power is around 1320 degrees at sea level. My 1600 Toyota engines were producing 248hp at 9600 rpm. Right, we are not racing the Tacoma’s, but would appreciate a good running truck, not one that stumbles along.

 

im an endurance mechanic
engines reach a different ' soak ' after hours (8.......12......24hrs) of runnin rather than sprints

no less its easier to tune a race engine than a street engine
Ur reference to an airplane engine that operates in a narrow rpm range ( seldom have i seen a cessna IDLE at 10kfeet. )
is specious

for all the competition iv been involved with
we Never idle a race engine.........................TO WHAT END wpould anyone idle a race engine??????
been in the pits of Porsche/ferrari etc .....seldom done
idling an engine 10.....12.....15k rpms below redline tells U nothing

i make an effort to stay away from the ' i .......... me ......singular anecdotal perfection '

the EPA programs are worth the paper they are printed on
no doubt w/o them we would build/produce an entirely different vehicle

toeing the line of a bureaucracy whereby some clerk could NOT tune to the criteria in a garage
is what toyota must do
or
they might decide NOT to build 2.7s

as well as U might know
ford on a dyno have had their i4 ecoboost over 600hp in race trim with predominant stock parts

simply would not be suitable for everyday bump/grind commuter use

toyota as a few b4 have copped out with the ' CVT ' engines
easier to tune to the EPA

the new ford ranger has what many others are trending to
8.......... 9.......... 10speed trans
there again keep the engine in a ' Narrow ' range
far easier to meet EPA requirements

 

I did build the engine in the only Viper to Finish the Daytona 24hr in 1999.

 

still more i / me ...................
im not want to make this personal

vipers are not that notable
many thought vipers had potential

lookin back
they were Unreliable & slow

v6's v8's 10's flat & v12's.................... the 10's over time the worst
10's simply dont seem to want to rev
8itre engin on adyno can produce #'s
yet get outrun All day/nite long

it was frustrating running a viper
team must hv had a huge supply o

simply not smart comparing street Tacomas to
airplane engines
race corrollas
slug vipers

 

Dude you know a lot, and seem very intelligent...

But I have hell trying to understand your posts with the way you type them out

 

not sure Ur question

iv mostly referred to the V10................no less i considered a slug

tho ive seen it pumped up to over 1000hp in various form
ive also seen diesel trucks with same HP
they weren't fast either

supossedly a rebirth with a V8 is in the works

HP is cheap with street cars running around with race car HP on the streetuit
virtually little to no limit how much race car HP two be made

many have bulit 12's V's & flats
bmw. / ferrari / konisegg / lambo
tho complicated few engines lend themselves to racing like a 12
and that glorious sound

427 vettes & chaparrals were not slow
427 Cobras / were not as sophisticated as either............... they werent slow
427 ford gt's were not slow (proved themselves at Le Mans a few times )

vipers had a modicum o success tho many had higher expectations
they will always have a wilting fan base

 

Thanks for the insight and tip.

 

Glad I'm not the only one.

 

People on here tired of me but this just happened to my 2018 with 32000 miles. truck still in shop over a week now. i have counted several in this forum and my dealer (mechanic) said they do several each year.

 

This could happen to any vehicle of any make an model ever. I'm sorry it happened to you, it most likely will never happen again to you with what ever you buy.

Please go in peace, friend.

 

I really don’t see how this is any different than second gen folks when they started bringing up rusty frames after the TSB and Toyota said they fixed and changed their process for making frames... it is something people should have the opportunity to read about.

 

Same here bud, 2018 with 35k and they’ve had it for over a week and still haven’t worked on it yet. They say that they’re going back and forth with corporate Toyota for guidance for what steps to take.

 

OK all you Smokey Unick's out there...Let's go back and read and analyze what the OP posted of the ....and I use the term loosely "mechanic" found.

THIS IS INTENDED TO BE SATIRE>>>

PERFORM VEHICLE INSPECTION. VERIFIED CUSTOMER CONCERN. FOUND VEHICLE TO HAVE CHECK ENGINE LIGHT ON. DURING INITIAL INSPECTION ALSO FOUND VEHICLE TO IDLING VERY ROUGH. PERFORM VEHICLE HEALTH CHECK. FOUND VEHICLE TO HAVE 2 CURRENT AND PENDING DTC. FOUND DTC P11EC00 FOR CYLINDER #1 AIR/FUEL INBALANCE (PORT) AND P1605 FOR ROUGH IDLING. FOLLOW TIS INSTRUCTIONS FOR P11EC00 DIAGNOSTICS. PERFORM ACTIVE SYSTEM TEST. CONTROL FUEL INJECTION VOLUME. DECREASE FUEL VOLUME IN 5% INCREMENTS. VIEW FOR VEHICLE TO SHOW MISFIRE ON INDIVIDUAL CYLINDERS. FOUND ALL CYLINDERS TO NOT MISFIRE BUT STILL RUN ROUGH. DECREASE FUEL TO -12.5 AND CHECK FOR SYSTEM OPERATION. VEHICLE STILL NOT MISFIRING. PERFORM EXHAUST GAS LEAK INSPECTION. RAISE VEHICLE AND PERFORM VISUAL INSPECTION OF EXHAUST SYSTEM AT BOTH BANKS TO CATALYTIC CONVERTER. FOUND NO SIGNS OF EXHAUST GAS LEAKS AT THIS TIME. PERFORM INSPECTION OF INTAKE SYSTEM. INSPECT INTAKE SYSTEM ON VEHICLE TO ANY LEAKS. FOUND NO LEAKS AT THIS TIME. INSPECT FOR AFTERMARKET INTAKE AIR FILTER. FOUND OEM AIR FILTER. INSPECT FOR DAMAGE TO MAF SENSOR. FOUND NO DAMAGE TO MAF SENSOR. REMOVE INTAKE TRACT AND AIR BOX ASSEMBLY. REMOVE SPARK PLUGS 1, 3 AND 5. PERFORM INSPECTION OF SPARK PLUGS. FOUND NO OBVIOUS SIGNS OF DAMAGE. SPOKE WITH SHOP FOREMAN(1057). SHOWED SPARK PLUG TO SHOP FOREMAN. SHOP FOREMAN SAYS SPARK PLUGS ARE NORMAL AT THIS TIME AND DOES NOT SHOW ANY DAMAGE TO SPARK PLUG. PERFORM SPARK TEST ON BANK 1. CHECK ALL SPARK PLUGS. ALL SPARK PLUGS AND COILS AT THIS TIME IS PRODUCING SPARK. SPOKE WITH SHOP FOREMAN ABOUT VEHICLE. SHOP FOREMAN ADVISES TO PERFORM COMPRESSION TESTING ON CYLINDERS. REMOVE BANK 2 COIL PACKS AND SPARK PLUGS. PERFORM COMPRESSION TESTING ON ALL CYLINDERS. FOUND CYLINDER 1 TO HAVE DRY COMPRESSION @ 120PSI. CYLINDERS 2 THROUGH 6 HAVE DRY COMPRESSION OF 180PSI. SPECIFICATION IS 199PSI AND ABOVE. PERFORM WET CYLINDER COMPRESSION TESTING. FOUND CYLINDER 1 TO BE @ 130PSI. FOUND CYLINDERS 2 THROUGH 6 TO HAVE COMPRESSION @ 210PSI. USE BOROSCOPE AND ATTEMPT TO SEE INTAKE AND EXHAUST VALVES THROUGH SPARK PLUG HOLE. UNABLE TO SEE CONDITION OF INTAKE AND EXHAUST VALVES AT THIS TIME. SPOKE WITH SHOP FOREMAN. SHOP FOREMAN ADVISES TO PERFORM CYLINDER LEAK DOWN TEST. PERFORM CYLINDER LEAK DOWN TEST ON CYLINDER NUMBER 1. FOUND CYLINDER 1 TO MAKE HISSING NOISE WHEN AIR IS APPLIED TO CYLINDER. APPLY 75 PSI TO CYLINDER. FOUND CYLINDER TO ONLY BE HOLDING ABOUT 35PSI. SHOP FOREMAN ADVISES TO INSPECT FOR LOCATION OF LEAK. FOUND LEAK TO BE ON EXHAUST SIDE OF VALVE ASSEMBLY. REMOVE BANK 1 SENSOR 1 AFS SENSOR. VERIFY LEAK TO BE COMING FROM EXHAUST SIDE. SHOP FOREMAN INSPECT TESTING RESULTS. AT THIS TIME RECOMMEND TO PERFORM ENGINE TEAR DOWN TO FURTHER INSPECT PROBLEM AREA. REINSTALL ALL SPARK PLUGS. REINSTALL ALL COIL PACKS. REINSTALL AIR BOX. RECOMMEND TO PERFORM ENGINE TEAR DOWN AT THIS TIME.

I will C&P interesting points of the tribulation of our mechanical hero and their love hate relationship with the SHOP FOREMAN

1) FOUND DTC P11EC00 FOR CYLINDER #1 AIR/FUEL INBALANCE (PORT) AND P1605 FOR ROUGH IDLING.
OK, THIS narrows down cylinder #1

2) INSPECT FOR AFTERMARKET INTAKE AIR FILTER. FOUND OEM AIR FILTER.
Good boy...you found where the air filter lives....is that really what is the issue on cylinder #1....?

3) SPOKE WITH SHOP FOREMAN(1057) Sighs....someone isn't all that educated at this point are they?

4) SPOKE WITH SHOP FOREMAN ABOUT VEHICLE.
Yet again said "mechanic" sees it fit to try to expand their mechanical knowledge from the Yoda of the shop...

5) "SHOP FOREMAN ADVISES TO PERFORM COMPRESSION TESTING ON CYLINDERS"
YAAAAAYYYYY shop foreman Yoda responds with proper instruction...

6) our hero does the cylinder wet/dry test and finds a clue...# 1 is down in all tests..

7) NOT AGAIN !!!! SPOKE WITH SHOP FOREMAN. Me thinks there is some sort of...."thing" going on with this relationship...
SHOP FOREMAN ADVISES TO PERFORM CYLINDER LEAK DOWN TEST.

8) PERFORM CYLINDER LEAK DOWN TEST ON CYLINDER NUMBER 1. FOUND CYLINDER 1 TO MAKE HISSING NOISE WHEN AIR IS APPLIED TO CYLINDER.
Well done Goober....

9) SHOP FOREMAN ADVISES TO INSPECT FOR LOCATION OF LEAK
I shouldn't call our hero Goober, as he was fairly competent in his automotive mechanical ability.
FOUND LEAK TO BE ON EXHAUST SIDE OF VALVE Our hero finally finds the culprit.

AND FINALY...10)
SHOP FOREMAN INSPECT TESTING RESULTS.
RECOMMEND TO PERFORM ENGINE TEAR DOWN AT THIS TIME.

I just cannot wait to read our hero's biography in this epic engine teardown... will the intense SHOP FOREMAN relationship continue or will our hero fall into the love hate abyss..


MY CONCLUSION:
AFR on cylinder #1 went bonkers causing the valve to take a hike.
Cause? No one here knows, a software issue on only 1 cylinder? A manufacturing issue on cylinder #1's exhaust valve only?

Stay tuned viewers...same bat time....same bat station....

 

Literally just spoke to another friend of mine today and his truck in the shop for same thing. Trading mine in whenever I finally get it back

 

can someone with some forum skills track down all the people on here that have had this problem and what year/mileage there trucks had. then start a sticky with this info?
they had this with 4th gen 4runner head gasket problems.
then for piece of mind. add the total trucks to how many ever hundred's of thousands of 3rd gens they have made in the last 4.5-5 years
then figure out what chance you have of having this problem.... or having covid and winning the lottery at the same time..

 

The people on here make up like 1 percent of tacoma owners. every little issue gets magnified on here so people think 9 out of 10 trucks have "issues" literally not the case.

 

Wow, now there’s a name from the past. "Smokey" Yunick (correct spelling) was ‘old school’.... one of the best!