Bad o2 or bad cat?

[Dustin Jackson]

@crownvic31 I think he is saying put the old cable back in. You said the problem started after you put the new battery cable in, so logically you would undo changes until you reached your baseline.

If you do have a vacuum leak it's possible the factory tune did a good job of compensating for it but now that you are on an aftermarket tune the leak is presenting itself more.

 

[crownvic31]

I will run another smoke test later today. My ladt smoke test i used the hose off the brake booster and sealed the end of the intake pipe with maf removed.

Any other suggestions on where to hook up my smoke machine?

 

[crownvic31]

Hello guys

So Just received an email from blackbearperformance in reference to the data log they received and my issue. His reply in regards to the data log was


"Fuel delivery (quantity) looks very very close to ideal. Fuel quality may be an issue though, as there is quite a bit of knock activity."

I gave him the brand and octane I'm using which is Exxon and sometimes BP and its always 93. Been running this one for years with no issue. I also replaced with explaining when this all started happening. Lets see what he recommends. I am at lost with this.

 

[crownvic31]

Im this folloing video i am trying to figure out the rear o2 sensors. To my understanding, they are there to tell is the cats are good or bad. With this reading of my 02 sensors, there is something going on.

Am i correct here or am i still at lost?

 

[j91z28d1]

I only see 2 o2 sensors and rpm on the graph?

are you wanting to look at the rear o2 sensor data?


edit. I missed is says sensor 2 yeah from what I've seen when working correctly sensor 2 is basically a flat line around 450mv

 

[crownvic31]

I only see 2 o2 sensors and rpm on the graph?

are you wanting to look at the rear o2 sensor data?


edit. I missed is says sensor 2 yeah from what I've seen when working correctly sensor 2 is basically a flat line around 450mv

Does this mean i should be looking into my rear o2 sensors and/or cats?

 

[j91z28d1]

well that's the thing.. cats are very expensive to replace. but yes, it looks there like your cats are catting lol. but the rear o2 sensors shouldn't have any effect on how the engine is running and it's running badly right? like bad gas mileage and rough running? seems like rather than throw a lot of money at new cats, and maybe melt down the new ones too. first I'd fix why it's running badly. and then if that doesn't change anything, you can have a look at the cats. if melted, then yes they need to be replaced or depending on your situation, you could just have the rear o2s turned off in the code.

cats get hotter depending on how rich the air fuel mixture is. if it's running rich enough they can get hot enough to melt the Platinum grid inside. restricting air flow and not doing the catalystic effect anymore.

 

[crownvic31]

Not sure if i mentioned this but i have long tube headers and high flow spun magnaflow cats which werent that expensive at 150 each. Tune was done by blackbear performance. Been running this set up for about 3-4 months now. I ran the escalade for a few weeks before getting the tune done. After the tune was done, everything was running well since 2 weeks ago after I replaced the power steering pump and the positive battery cable. Then escalade started running funky.

Reading about the symptoms of bad rear o2 sensors and what im experienceing, i can match a few with mine symptoms.

Noticeable Loss of Fuel Efficiency
Sulfur smell from Exhaust.
Engine bucking/jerking
And the readings from my rear o2 sensors are not the same.

As per the catalytic converter, i read this:

"A clogged converter can make your vehicle misfire and accelerate slower. When the material breaks up inside of the converter, it blocks the exhaust and creates backpressure on the engine, causing it to misfire. "

I yet have no codes.

 

[crownvic31]

Here are some pics of how my exhaust is set up.

 

[crownvic31]

Sorry for all the post guys. Im just trying to educate myself here and just ask for advice and opinions.

So in the email sent by blackbear performance, he mentioned that there was knock activity and questioning my gas.

So reading more i came across this:

"a bad catalytic converter can potentially cause a knock sensor code. A failing catalytic converter can lead to an increase in exhaust back pressure, which can in turn cause abnormal engine combustion and trigger a knock sensor code"

Now i do not have a code. But this can be the cause to why he was able to see knock in my data log. Also, the vacuum leak i here coming from the orfice(pcv valve) which is not a vacuum leak because ive done several smoke test and the engine is sealed, this might be that extra exhaust back pressure?

Hmmmmmm