[AlecB]

Block on right shows vehicle idling with little to no erratic data in B1S2.

Previously vehicle was driving. I highlighted 2 areas that do show erratic data relative to B2S2.

Thoughts?

 

[AlecB]

jnissen -
2010 EX-L with 188k mi. Oil burning issues from VCM with frequent park plug fouling. Recently disabled VCM. I understand this is a reason to suspect cat failure.

bbrages -
Current on upstream sensor shown to help diagnose the issue. Most videos I saw said to compare the upstream to downstream sensors. Upstream should fluctuate rapidly between 0 and 1 V while downstream should remain fairly steady around 0.5-0.7 volt.

This car doesn't provide upstream data in volts so I'm having trouble interpreting.

It does give upstream sensor data in mA which rapidly fluctuated from -0.03 to 0.03 at idle and steady driving, and jumped as high as 4mA when throttle was quickly let off. Bank 1 and 2 upstream sensors were nearly identical. I later adjusted the graphs to only show data from -0.1 to 0.1 and the rapid up and down as the upstream sensors checked fuel trim was evident.

Both downstream sensors were relatively stable at idle, but rapidly dropped when throttle was quickly let off. Bank 1 sensor 2 showed no significant difference at idle compared to B2S2, but did show significant difference at steady throttle as I highlighted.

nitely2-
I'm aware of a few related posts but was specifically looking for how to interpret the live data. The non-fouler is new to me. Thanks for sharing!

~~~~

In other news I bought an IR thermometer and measured the cat temps. Unfortunately I couldn't get a reading upstream of the bank 1 cat that is triggering the CEL, there just simply wasn't the room to get the thermometer behind the engine block to take the reading. I didn't try taking the bank 1 upstream temp from under the car, so maybe I can figure out a way to do that.

I did get readings on the Bank 2 cat and the 3rd combined cat and on those the downstream temps lower than upstream, which I understand to mean the Cats are not working properly. On the other hand, in the live data both bank 1 and bank 2 cats are reading almost identical temps (range:675-1460*F average:1000-1100*F) at normal operating temps, so that doesn't seem to indicate that the bank 1 cat is worse than bank 2 cat, even though only bank 1 cat is triggering the check engine light.

I'm not sure if I should interpret that to mean that all 3 cats are in similar poor condition and should be replaced, or if it means that all 3 cats are in similar poor/old condition, and the fact that only the bank 1 cat is triggering the CEL means that the O2 sensor may be the issue.

 

[AlecB]

I'm also seeing this which is starting to make some sense...

http://www.urvi.net/forumfiles/SB/A14-002.PDF

 

[AlecB]

I'm also seeing this which is starting to make some sense...

http://www.urvi.net/forumfiles/SB/A14-002.PDF

Not that, all the sensors are intact. Scrubbed them off with a brass brush.

 

[AlecB]

When you installed your "muzzler" did you install new plugs? And per suggestion by nitely2 replace O2 sensor.

Good point.

I did, but not NKG's. I was fed up with paying for 6 new NKG plugs every 5-10k miles so I installed some cheap ones. I've been meaning to replace those with NKG's now that I've muzzled it and fixed an oil leak from the VVT gasket.

 

[AlecB]

In other news I bought an IR thermometer and measured the cat temps.

I got better readings. Found the bank 1 cat to be the only one that had higher readings after the cat... not sure how to interpret that.

 

[AlecB]

Pulled the brand new spark plugs and found burned oil deposits on the anode, oil on the threads, but not on the coil packs for all of bank 1. I popped into my local dealer to price a piston ring cleaning job and a valve seal replacement job to see if either would be worth it, and a service writer said that its almost certainly the piston rings and not the valve seals even if all 6 cylinders are having equal and excellent compression at 150psi.

Given the VCM issues with the engine, I'm presuming the oil control rings are still letting some oil through which is adding oil to the combustion chamber on bank 1 but not bank 2 even with VCM disabled. I had been seeing some large differences between bank 1 and 2 upstream sensors, which I thought might explain the differences in the downstream sensors. I presume the oil in the combustion chamber on bank 1 due to the oil control ring leak is causing the bank 1 sensor to produce more variable numbers and have a slightly more lean long term fuel trim than bank 2. The oil in the combustion chamber then enters the bank 1 cat and killed it. The bank 1 sensor 2 is reading that the cat is below threshold when driving, but not at idle so its not totally destroyed. Hopefully the 3rd cat is taking care of any bad gases (it passed tailpipe emissions recently, but I moved to a OBD2 emissions inspection state) I installed spark plug non-foulers on bank 1 sensor 2 which didn't change the live data much, but has kept the bank 1 catalyst monitor from failing so far.

I added some Seafoam top engine cleaner spray to the bank 1 combustion chambers but I'm still getting oil on the spark plug threads. I'm still debating whether I should try and EPR flush the engine oil to address the oil control rings, or just let it be and hope the non-foulers get the car to pass emissions next year. The car is too old to have the rings pulled out and cleaned. I'm hoping that disabling the VCM stopped the majority of the oil burning problem and that maybe after a few thousand more miles without VCM, normal operation, and frequent oil changes, the rings might unstick themselves. I might also try liquid seafoam rather than the spray. Engine oil flush seems like the next reasonable step, but also seems a little risky on an engine with 190k miles.

 

[AlecB]

Do not run an engine flush. You'll be in a world of hurt if you do.

Care to expand? Anything to worry about other than the oil pump system getting clogged up?

I was considering pulling the oil pan and intake tube before and after flushing it to make sure there was nothing serious already floating around in there. Ericthecarguy has a scary video of and oil pump system failing that he blamed on chemical engine flush treatment, but I figured I might be able to get ahead of that by manually cleaning it out before and after the chemical treatment to remove any sludge or shrapnel.

I know there's something to be said about leaving well enough alone and burning a little oil is to be expected at 190k miles...

 

[AlecB]

I have read about people fixing oil burning by removing the plugs and putting a strong cleaner (Berryman B12, I think) in the cylinders. Seems to work, might be more challenging in a V engine.

Yea I thought about that. I presumed it would be best to manually crank the engine to halfway between TDC for any two cylinders so that no cylinder was at TDC to add the cleaner in. After that, manually wiggle the crank back and forth a bit once a day for a couple days to help the cleaner penetrate. Before adding spark plugs back in, use the key to turn over the car a few revolutions so that any residual cleaner gets blown out the spark plug holes to avoid hydrolocking. Install spark plugs and go for it?

 

[AlecB]

Non-foulers are very effective at making a P0420 go away.

The way I understand it, the engine maintains a balanced mix of fuel and air by trimming the amount of fuel injected to constantly alternate between too rich and too lean as read by the upstream O2 sensor. So if you plot upstream O2 sensor voltage, you'll see it switch between high and low every second or so as the engine relies on this "feedback loop" to keep the mixture correct.

The downstream O2 sensor measures oxygen after the cat. If the cat is doing nothing, you'd expect to see the same shape on the voltage from the downstream sensor. If the cat is working, the downstream sensor should be a flat line. The non-fouler pulls the downstream sensor out of the exhaust stream so that its result looks like a flat line.

This is also why replacing the downstream sensor doesn't typically fix a P0420.

You might find this interesting.

This is data before non-foulers while driving at highway speeds. Bank 1 long term fuel trim is consistently 0.5-1% leaner than bank 2. B1S1 is consistently more variable than B2S1.

After adding the non-fouler to B1S2, the data looks very much the same, but less variable. Definitely not a flat line, still more variable thank B2S2, but not bad enough to trigger the catalyst monitor.

 

[AlecB]

Thanks for the suggestions Odyfamily. Ive added some techron, but have been scared away from oil treatments other than more frequent changes. Good to know theres a less harsh alternative. Is Rislone something you can leave in the oil for the entire oil change interval?

Heres something folks might find interesting. Live data before and after adding a sparkplug nonfouler. In some ways the B1S2 appears worse, but the b1 catalyst monitor hasnt thrown a code yet.

 

[AlecB]

Good news, looks like the Seafoam cleared the piston rings.

3 days ago I used 2 rounds of Seafoam Spray Top Engine Cleaner sprayed directly into the combustion chamber through the spark plug holes on cylinders 1:3 where I was finding oil on the spark plug threads. First round had much more smoke than the second, and the car even coded a flashing CEL misfire on multiple cylinders and bogged down trying slowly up a hill to get to the main street. Once I turned the car off and turned it back on again, it had ignition on all 6 cylinders. Ran the car "spiritedly" 20 minutes after each round with 8hrs between rounds. After the 2nd round I pulled the spark plugs and there looked to be some fresh oil on the threads.

~100mi of driving~

Today, I prepped to soak the cylinders in Barryman's B12 for 24hrs and then change the oil with some Rislone added in. Much to my surprise, the spark plugs came out dry and healthy looking. Since I already had the plugs out and the car jacked up, I added some B12 and wiggled the crank back and forth, which I'll continue to do a few times today. Presumed it couldn't hurt anything. After it gets dark tonight I'm going to run the car at highway speeds for at least 30min then change the oil adding Rislone.

I really appreciate everyone for the suggestions and the wealth of knowledge on this website. I always thought of Seafoam as a last ditch effort snake oil. Happy to be proven wrong. 185k mi of VCM oil gunk and spool valve leaks that the dealership wanted to total the car in maintenance over got cleared up by $200 for seafoam, a couple of oil changes, and a VCM-tuner.

Looks like my bank 1 warm up catalytic converter is just bad enough to fail OBD2 emissions, but I'm going to sleep better knowing the cause has been fixed, and that the non-foulers will keep the van passing emissions. Maybe getting the cat really hot a few times this summer will burn off enough crap to bring it back to life a bit, and there's always that 3rd cat to clean up what the others miss.

 

[AlecB]

the engine was really running rough, it almost seemed like it was misfiring

I'm no mechanic but I attributed it to fouled spark plugs from piston ring blow-by the first time I gave it some throttle after the Seafoam, which caused the computer to turn off the ignition coils on those cylinders. I did have a flashing CEL until turning the car off. As soon as the car restarted 10 seconds later, it roared to life like nothing happened.

I've seen cars run rough after seafoam, but not to the point of misfires and stalling.

The CEL coming on suddenly and staying on until the car was restarted struck me as electrical/computer related.

 

[AlecB]

More reason to believe the oil control ring leak was the source of my catalytic converter dying, and that it has now been solved with the seafoam treatment. Attached data is both from highway cruising. Note the imbalance in LTFuel trim* and the more variable B1S1 data in the before snapshot as compared to B2S1 which now shows the more similar values after seafoaming the rings. These snapshots also show before and after adding the non-fouler to the bank 1 cat and you can see some improvement, but non-foulers are definitely not a perfect fix.

*I noticed after posting that the before snapshot shows STFuel trim whereas the after snapshot shows LTFuel trim, so you'll have to take my word for it that LTFuel trims in bank 1 were consistently 0.5-1% lower than bank 2.

Before seafoam and B1S2 Oxygen sensor non-fouler

After seafoam and B1S2 Oxygen sensor non-fouler