Hello. I own a 02 Toyota land cruiser pick-up i use to go off road. I have been having it for 3 years. (6 cylinder petrol) manual transmission.
As soon as i purchased it 3 years ago I replaced the original manifold with an after marker manifold and removed the cat. converter, (muffler is still in place) both O2 sensors also removed. the vehicle was running smooth with no issue or smell and good torque for a solid 3 years.
A couple of months back I have starting having heavy carbon smell from the exhaust especially when i accelerate. the smell usually travel inside the car only when i have the windows down during deceleration. I also have excess black smoke when revving the engine to its limit.
i have done/observed the following:
cleaned fuel injectors.
cleaned the throttle valve and body.
replaced the spark plugs
Oil level is not decreasing (not burning oil)
coolant level not decreasing (no possible head gasket leak)
no rattling noise/loud noise (possibly no exhaust leak but i have not really checked)
the car still have good torque
no rough idle
black soot can be observed in the parking lot floor from the exhaust especially after cold start
Engine oil has some black residue that appeared after cleaning the injectors
the smell is only from the tail pipe, when windows are up no smell. only when windows are down.
Smell appeared suddenly after taking a 1 day tour off road.
Added fuel injector cleaners and many other additives into the gas tank to remove the carbon build up
drove the car at high RPM/speed to blow off the carbon
with all said above the problem still exists, does anyone have any advice
With no signal from the oxygen sensors, the ECU remains in open loop mode, which cannot adjust to different operating conditions. The only solution is to restore the exhaust to its original configuration.
I’m surprised it ran well with both 02 sensors removed. Post cat shouldn’t matter (as far as driveability), but the pre cat 02 delivers important info to the computer. I had a 93 Silverado that I bought in that condition. Ran weird, and bucked like the fuel was cut off when warming up until I welded in a bung and installed a pre cat 02.
I agree that removing the catalytic converter will not cause any driving problems.
Removing both O2 sensors wasn’t smart.
For driveability reasons, you need to at least put the upstream sensor back in.
As Tester noted, with the downstream O2 sensor removed, unless you used a spark plug non-fouler to fake-out the sensor, your light will always be on, making it difficult to know what else is wrong.
You’ve not mentioned anything about verifying your coolant temp is up the correct temperature.
Here’s my suggestion:
Put a new upstream O2 sensor back in, and drive it through multiple drive cycles.
Get your OBDII codes read and post them back here. The missing downstream O2 sensor will obscure the data a little.
If removing the O2 sensors and converter were going to make a problem with black smoke it would have done it right from the start.
I figure he’s been ignoring the check engine light for 3 years.
With no O2 sensor the engine has been running on a default fuel map.
Not ideal, but good as a carburetor I’m sure.
Again, if there were going to be driveability problems they would have appeared 3 years ago.
I’d scan for trouble codes (besides for O2 sensors), do a compression test, check for fuel pressure drop after shutdown, due to a leaky injector.
Correct. I wonder if the computer doesn’t get data where it can from the remaining sensors to determine fueling, etc, though. I wouldn’t think it would just ignore all sensors when one is removed. With the check engine light always on, maybe another sensor has failed that’s causing the issue? Seems like it would be easier to diagnose with that upstream 02 put back into service.
When the computer doesn’t get a signal from the up-stream O2 sensor, it substitutes a default value.
This value is a richer mixture so as not to damage the engine from running it too lean.
That’s where the soot/carbon is coming from.
With the O2 sensor removed, your ECU can no longer calculate how much fuel should be injected . The ECU will fallback to its default value and always inject the same amount of fuel every time. This could cause either low performance or horrible fuel economy.
the only thing I can think of is that it did it from the beginning. just not as bad and OP did not notice it. now with all that extra fuel washing the cylinder walls slowly over time has affected the cylinders making it a lot worse.
Are you in the USA? All the answers I’ve seen above seem to assume so. My guess is that you are not because you referred to a petrol engine and it’s a pickup, not SUV. I don’t recall seeing a Land Cruiser with a pickup body in the US for a long, long time. I think the FJ45 was the last one sold here.
I don’t think the default mapping is so grossly rich that it would make black smoke.
If there’s still data for rpm, temperatures, MAP or MAF sensor the computer can still come up with a close approximation, better than a carburetor at any rate.
p.s. What the OP describes is an overly rich mixture, not carbon buildup per se.