Where exactly is the catalytic converter

[toolpusher]

Hi,

I was wondering what part exactly is the catalytic converter?
I thought they are the can shaped boxes marked with the question mark in my picture.
But because the rear oxygen sensor is located before those boxes, does it mean the actual converter is in the section with the flex pipe?

I am asking because for our high mileage XC90 with a potential bad catalytic converter I am considering as a last resort to drill a little hole in the pipe right in front of the converter, flood it with carburetor cleaner and squeeze a bit more life out of the car. Saw a promising video on Youtube on that "technique".

[RickHaleParker]

The V8s have 4 catalytic converters. Yamaha's solution to the Ultra-low-emission vehicle (ULEV II) standard.

The O2 sensors monitor the front two catalytic converters but not the back two.

Look closer all four O2 sensors are up by the front catalytic converters.

What makes you think it is the catalytic converters? A lot of people misinterpret the DTCs and mess with the catalytic converters when the problem is something else. Post the codes.

[toolpusher]

It's my understanding that O2 sensors are placed before AND after a catalytic converter.
So you are saying all 4 sensors in the picture are before the catalytic converter and the car has even more downstream?
Btw, my engine is 3.2.

I believe it is the catalytic converter, because the CEL comes on and goes off after treatment with cat cleaner or sometimes just my driving a tank full of premium fuel. I tend to think that's a pretty strong indicator that the catalytic converter is right at the edge of performing at threshold, and it is not something other like air intake, ignition coil or exhaust leak.

[ggleavitt]

Per VIDA for the B6324 (6 cylinder) engine:
"There are four catalytic converters, two for bank 1 and two for 2. Bank 1= cylinder 1, 2, and 3. Bank 2= cylinder 4, 5, and 6. The two [bank related] heated oxygen sensors are used to control the catalytic converter; one heated oxygen sensor in front of the catalytic converter in the engine compartment (front heated oxygen sensor) and one heated oxygen sensor after the catalytic converter in the engine compartment (rear heated oxygen sensor). After the rear heated oxygen sensor there is another catalytic converter, located at the front of the propeller shaft tunnel under the vehicle's floor. However, this catalytic converter is not monitored."

If you can get yourself a copy of VIDA running on a PC (do an internet search for "VIDA 2014A image"), you'll have a pretty good idea what to look for with your issue.

What codes are being produced and why would this not be at least in part a sensor problem?

[toolpusher]

Thank you so much.
So the monitored converters are manifold converters.
Didn’t think of the possibility that there are unmonitored converters downstream.

How could sensors be positively influenced by a catalyst converter cleaner or the detergents of premium fuel?

The code is the generic P0420.

[pgill]

Btw, my engine is 3.2.

Tool Pusher,

Now you have my attention.

I own two 3.2's (a 2008 and a 2010) with Zero P0420 codes

My Neighbor had a P0420 (on his Toyota) and I solved it by using the same type of sparkplugs that Volvo used in later 3.2s


Here is what I would do to solve your issue

1. Get Denso Iridium TT 4704 (Just install them at the .040" gap)

2. Replace the Thermostat (when these fail they cause extra strain on the ignition system)

3. Verify that the PCV is functioning correctly (remove the oil fill cap at idle, the idle speed shouldn't change)

4. Replace the 6 intake gaskets (I've used aftermarket Victor Reinz LR001454 gaskets and they are in expensive and very high quality)


Supporting information

Denso Iridium TT

https://www.freel2.com/forum/topic35846.html

Thermostat

https://www.volvoxc.com/forums/showthre ... -2009-XC70

viewtopic.php?f=31&t=86205&start=10



Manual explaining how the code is set

Go to page 8 and 9 (it explains how it works)

MY07B6324S-S80XC90AWD (1).pdf

(603.47 KiB) Downloaded 575 times

Conclusion

If the switching from Lean to Rich and then back again from Rich to Lean is detected in the second O2 sensor earlier than 0.022 seconds after it was detected in the first then the code will be set. That's faster than a blink of an eye. The engine is adjusting the air fuel ratio to check the efficiency of the converter. However if the combustion isn't complete then it can interfere with the measurement. A lean mixture is more difficult to ignite, this is where the Denso Iridium TTs come in, this ultra fine tip plug is better at igniting the mixture under these difficult conditions. And a broken Thermostat can also interfere with the efficiency of the coil packs and the ignition of the lean mixture.

Both of my 3.2s have had their Thermostats replaced at the 10 year point. And one was broken before I replaced it and the other broke sitting on my shelf before I could install the new part. The broken one didn't set any codes but I suspect if I continued to operate with a broken Thermostat I would have eventually ended up with a code likely a P0420 just like you.

Good luck

Paul

[RickHaleParker]

The code is the generic P0420.

P0420 is “Catalyst System Efficiency Below Threshold". There are things other then the cats that can push the System efficiency below the threshold. If you go after the cats now there is like a 99.5% chance you will be wasting your time and money.

Is P0420 the only code?
How many miles on the Odometer?

Possible source

• Air leak in the exhaust system.
  Damaged front heated oxygen sensor.
  Damaged front catalytic converter.

[SuperHerman]

First let us discuss your photos so you understand the parts. Under the Big Bold lettered title "O2 Sensor Ports" are four red arrows. The first two arrows, from left to right, point to the Front Bank (1 and 2) O2 sensor locations. Immediately behind said ports you will see the exhaust manifolds swell up wide and then turn into a flange. These are the main catalytic converters and the ones that the system monitors.

In the diagram you circle two wire mesh parts of the exhaust system - said circled items are the flex pipes. They are just a flexible air tight mechanism which allows movement and the like for the exhaust system. Using straight metal tubing doesn't seem too work well, I assume it is because of movement and heat expansion.

Back to the diagram and the 3rd and 4th red line arrows - those point to the down stream, post catalytic converter, O2 sensors which monitor how the catalytic converter is operating.

Next in your picture you have a red ? mark - those two items are another set of catalytic converters added for greater emission control, but other than potential back pressure issues which impact the other O2 sensors, if failed/failing, they are unnoticed in the system.

Volvo converters are pretty darn good. They should not fail unless the engine has an issue. On higher mileage cars it could be caused by oil burning caused by age of cylinder rings. Usually the cause is something else and then neglect as the car "runs fine". The air fuel system starts attempting to control things and the end result is destruction of the converters.

What the others have said regarding possible causes holds. If the light is on it usually is another problem and if the problem(s) are repaired quickly no damage will be done. There are cases where excess oil from normal wear in a high mileage engine will clog the converters and cannot be cleaned.

[toolpusher]

Thank you all. I think what threw me off was that on the pages for ordering parts that I checked, the downstream twin pipe was shown when searching for catalytic converters.
And then I couldn’t get my head around the positioning of the sensor. An unmonitored converter didn’t occur to me.

I’ll check the PCV valve and otherwise invest in a proper diagnosis by an independent Volvo shop and take it from there.

[pgill]

Toolpusher

You are going to have to change your user name if you are going to have someone else fix it. LOL

Just kidding.

In all seriousness on a different Thread you were advised by a Garage that the OAD pulley wasn’t likely to fail.

For me I have had 100% failure on 10 year old OAD pulleys. And I am not the only one.

To be completely honest I wouldn’t let that garage change the oil on my 3.2.

As long as you are going to a different shop for the diagnostic then I agree with your plan.

The biggest impact to your catalytic converter code will be the Iridium TT spark plugs. I wish I knew someone at Volvo that could confirm why Volvo switched to the TT style plugs. It may have been for fuel economy or more likely it was for emissions.

After that the PCV. But you should be able to check yours just removing the Oil cap to the engine. Volvo likes to keep the engine very close to atmospheric pressure. If you remove the cap and it sucks in lots of air then it’s broke or if it is blow out air like a steam locomotive it’s also broke.

Don’t forget to change the Thermostat. The plastic housing breaks overtime and it should be replaced every 10 years or so.

Good luck

Paul