Running rough under load

[hammerheadfistpunch]

So I have been posting a lot about a vibration I was convinced was suspension or drivetrain. I'm coming to the conclusion that I think its either transmission or engine and I need your help.

So here is the data

HG and top end rebuilt at 220k, now at 298k
Injectors were flowed and balanced at that time, they were rebuilt with new seal as needed by RC engineering
since then a single injector was replaced due to damage from shorting a lead against the intake. OE new replacement
fuel filter (engine) is less than 60k old.
PVC valve was replaced about 50k ago
the little "fuel filter" (the one on the top of the intake) was replaced then as well.


symptoms

A little rough idle, not too bad but it "farts" a little at the exhaust pipe, not a miss, but a little rough
"grrrrrs" on acceleration, sometimes worse than others. Normally the 1FZ "mooos". Feels like a missing injector but much less severe.
Associated with a vibration felt inside.
Power is a little low on low rpm but doesn't seem overall down on power
Hot exhaust
Doesn't show any problems revving out of gear, there is a slight "warble" from 1800-2600 if you hold the throttle there out of gear.
Smells rich and hot.

What I've checked so far

I just replaced the spark plugs (image below) and they looked fine on all cylinders, no odd patterns
Checked the MAF for Resistance and voltage per FSM and its in spec.
Checked the upstream and downstream O2 for resistance per FSM and in spec.
Been keeping at eye on both the short term and long term fuel trims. (images below)
Temps seem to be in line with reality (based on ECU scan) so I don't suspect its a bad sensor there.

My theory is that its its running lean or rich for whatever reason but I can't see any strong symptoms of this.

Not burning coolant, burns a small amount of oil.

I will try and get some audio of the symptoms.

Where can I look?

 

[hammerheadfistpunch]

as for the transmission - No leaks, shifts firm, fluid is red and doesn't smell burnt. The only reason I suspect this is because of a possible torque converter issue since I can rev the engine without complaint out of gear.

 

[Rifleman]

How long has it been since you last changed your O2 sensors?

 

[hammerheadfistpunch]

How long has it been since you last changed your O2 sensors?

Never but I got the truck at about 220K and they were new then. it was obvious they weren't original. I know people jump right to the sensors but they read right for resistance and they are giving proper voltages as far as the computer is concerned so I have a hard time blaming them.

 

[Rifleman]

Just because they read the correct resistance doesn't mean that they are not getting slow in their switching response, rich to lean, lean to rich. IIRR the type of O2 sensor used on our truck should be replaced about every 100,000 miles. It should be part of a regular maintenance scheduled.

 

[Rifleman]

Here is some more info for you from the net.
Oxygen Sensors are Service items, not Repair items. Don't Wait For Failure!

Oxygen sensors are very important engine management components and are a critical part of the vehicle emission control system. That’s why checking and if required replacing a worn out or ageing oxygen sensor should be an important part of every routine service.

A faulty, worn, underperforming or damaged O2 Sensor can:

• Lessen engine performance, causing vehicle coughing, surging, hesitating, rough idling or stalling. Lack of power and poor driveability may also result.
• Increased fuel consumption. Failed or poorly operating oxygen sensors can cause a substantial drop in fuel economy
• Increase dramatically exhaust emissions
• Cause Possible engine damage
• Cause Catalytic converter failure
• Activate the Check engine light

Oxygen sensors should be inspected and replaced at the manufacturers recommended service intervals. Vehicle manufacturers recommend periodic inspection and replacement of oxygen sensors. Also see why replace oxygen sensors for more information.

Replace Your Oxygen Sensors as part of your Preventive Maintenance Program

As there are several types of oxygen sensors expected service life can vary significantly.

Typical maximum service life:

• 1 or 2 wire Oxygen sensors - have a typical service life of 30,000 miles
• 3 or 4 wire Oxygen Sensors (Thimble type) - have a typical service life of 50,000
• Planar Type (Thick film) Oxygen sensors- have a typical service life of 92,000 miles

 

[hammerheadfistpunch]

Just because they read the correct resistance doesn't mean that they are not getting slow in their switching response, rich to lean, lean to rich. IIRR the type of O2 sensor used on our truck should be replaced about every 100,000 miles. It should be part of a regular maintenance scheduled.

Well I feel like I should replace them just so people will stop asking, though I'm not convinced it's them.

 

[Rifleman]

Well I feel like I should replace them just so people will stop asking, though I'm not convinced it's them.

Changing them would be up to you, but i know from working on customers cars, changing them can make a difference. I've had performance problems on some cars where the O2 sensor checked out per the manual, but the driveability problems were still there. Once i changed the O2 sensor the problems went away. Now i will tell you, 99% of the time customers would say why are you changing a "good sensor" that costs so much money. I'd tell them, even though the manual says it's good, doesn't mean that it's not wearing out, and getting slow in responding to load changes in the motor. After the customer would spend the money for new sensors, and their drivability, and fuel mileage returned, they were happy "they decided" to spend the money for new sensors, the customer is always right, Ha Ha!

 

[hammerheadfistpunch]

Changing them would be up to you, but i know from working on customers cars, changing them can make a difference. I've had performance problems on some cars where the O2 sensor checked out per the manual, but the driveability problems were still there. Once i changed the O2 sensor the problems went away. Now i will tell you, 99% of the time customers would say why are you changing a "good sensor" that costs so much to replace. I'd tell them, even though the manual says it's good, doesn't mean that it's not wearing out, and getting slow in responding to load changes in the motor. After the customer would spend the money for new sensors, and their drivability, and fuel mileage returned, they were happy "they decided" to spend the money for new sensors, the customer is always right, Ha Ha!

I'll put the densos in my rock auto cart tonight. Do I need gaskets or special tools?

 

[gsdog2]

I have a 95...#6 injector went out causing similar symptoms. Changed all of them. Good to change your O2's. Easy plug and play. The 2 nuts are probably rusted out, so that was my only issue. They still turned to remove the sensor.

 

[hammerheadfistpunch]

I have a 95...#6 injector went out causing similar symptoms. Changed all of them. Good to change your O2's. Easy plug and play. The 2 nuts are probably rusted out, so that was my only issue. They still turned to remove the sensor.

When my injector went out it was way worse, but a similar feeling. Running on 5 I got a light and it was a night and day difference to drive, it's not that bad.

 

[Rifleman]

No special tools needed, but before you spend the money with Rock Auto I'd check with Toyota. The reason i say that, when i just replaced the ones on my LC, the factory ones were a few dollars less than the Denso's from Rock Auto, plus the factory ones came with new nuts, and gaskets. Believe me, you'll NEED NEW NUTS, the factory ones are almost always eaten up to the point where there are no flats left on them.

 

[hammerheadfistpunch]

No special tools needed, but before you spend the money with Rock Auto I'd check with Toyota. The reason i say that, when i just replaced the ones on my LC, the factory ones were a few dollars less than the Denso's from Rock Auto, plus the factory ones came with new nuts, and gaskets. Believe me, you'll NEED NEW NUTS, the factory ones are almost always eaten up to the point where there are no flats left on them.

I'll check with @beno in the am, thanks

 

[cruiserdan]

CEL?

 

[hammerheadfistpunch]

CEL?

Nope.

 

[cruiserdan]

Disappearing coolant?

 

[hammerheadfistpunch]

Disappearing coolant?

Nope.

 

[Tools R Us]

Air intake tube, cracked, age, condition?

 

[hammerheadfistpunch]

Air intake tube, cracked, age, condition?

Hard to say but it looks to be fine. I wrapped it it heat wrap a while back to prevent it from getting too toasty and it's still pliable

 

[inkpot]

Did you do a compression check when you swapped out the spark plugs?