[Babyfood1217]

Vehicle: 2002 Sport SR5 - EPA emissions (non-CARB)

Recently had my rear cat stolen, and just had a chance to install the replacement parts last night (pretty much all Walker stuff). New O2 sensors (upstream AND downstream) along with the new cat and muffler. New exhaust gaskets at each joint.

Fired it up, and now my RPM pulsates. At idle, during acceleration, and during steady throttle, there’s an a consistent pulse in the RPM, regardless of where the needle is on the tach. Pulse seems to be between 50-100rpm, according to a visual check of the tach, and according to a couple different OBD reader apps on my phone. No codes are being thrown, no CEL, and per the apps, all parameters look to be good. (I have an ELM327 reader, and have used DashCommand, CarScanner, and inCarDoc apps).

Vehicle ran fine before this theft, this has appeared only after new parts install.

Despite getting no codes to suggest there being an issue, I’m tempted to get a new MAF, since a lot of folks refer to it being a culprit when tracking down RPM issues (though I haven’t read of a problem matching mine).

Any thoughts? When new O2 sensors are put in, do you have to replace other bits at the same time? Or reset anything (I’ve swapped O2 sensors before, but don’t recall resetting/changing other stuff). Do new catalytic converters break-in in such a way to that would cause this type of pulsing RPM issue?


Sent from my iPhone using Tapatalk

[brillo_76]

What year of 3rd gen emmisions are we dealing with?

Sent from my SM-A505U using Tapatalk

[diverscale]

my guess is that your first o2 sensor needs replacement

[Babyfood1217]

Originally Posted by brillo_76

What year of 3rd gen emmisions are we dealing with?

Sent from my SM-A505U using Tapatalk

Oops, edited above, but EPA non-CARB.


Sent from my iPhone using Tapatalk

[Babyfood1217]

Originally Posted by diverscale

my guess is that your first o2 sensor needs replacement

I put in a brand new Denso for the upstream sensor. I can wrap my head around new parts being crap, but would that explain the specific symptoms I’m experiencing? When o2 sensors have gone bad before, I’ve at least gotten a CEL. (The downstream was an aftermarket, that what the shop had at the time)


Sent from my iPhone using Tapatalk

[Bad Luck]

Originally Posted by Babyfood1217

I put in a brand new Denso for the upstream sensor. I can wrap my head around new parts being crap, but would that explain the specific symptoms I’m experiencing? When o2 sensors have gone bad before, I’ve at least gotten a CEL. (The downstream was an aftermarket, that what the shop had at the time)


Sent from my iPhone using Tapatalk

Where did you buy the Denso oxygen sensors from? What part numbers did you buy?

[brillo_76]

Did you buy your sensor from Toyota, Rock auto or an auto-parts store? As its quite possible if you didn't you got a counterfeit one. Thus why it doesn't work properly.

[Babyfood1217]

Originally Posted by Bad Luck

Where did you buy the Denso oxygen sensors from? What part numbers did you buy?

Originally Posted by brillo_76

Did you buy your sensor from Toyota, Rock auto or an auto-parts store? As its quite possible if you didn't you got a counterfeit one. Thus why it doesn't work properly.

Denso #234-9002

Purchased off Amazon last year as I had some credit I wanted to use and thought I would stockpile some regular maintenance stuffs, just never got around to doing it. Sensor has been sitting in its box ever since.


Sent from my iPhone using Tapatalk

[Babyfood1217]

Originally Posted by Babyfood1217

Denso #234-9002

Purchased off Amazon last year as I had some credit I wanted to use and thought I would stockpile some regular maintenance stuffs, just never got around to doing it. Sensor has been sitting in its box ever since.


Sent from my iPhone using Tapatalk

Sent from my iPhone using Tapatalk

[Babyfood1217]

I’m kinda going a through a crash course in vehicle issue diagnosing here, so I wonder if what I’m experiencing is the phenomena often referred to as “hunting”?

I just read a reference to trying to isolate the issue by unplugging the o2 sensor, causing it to go into an “open loop” state. A CEL would likely come on, an there would likely be a loss of power, but if the “hunting/surging” also disappeared, that could be a good indicator that it is indeed a faulty O2 sensor. Does that sound right, or am I understanding that concept correctly?


Sent from my iPhone using Tapatalk

[Bad Luck]

Originally Posted by Babyfood1217

Denso #234-9002

Purchased off Amazon last year as I had some credit I wanted to use and thought I would stockpile some regular maintenance stuffs, just never got around to doing it. Sensor has been sitting in its box ever since.


Sent from my iPhone using Tapatalk

That's the correct part number, but amazon and ebay are full of knockoffs so it could be a bad sensor. Do you still have the old sensor?

[Babyfood1217]

Originally Posted by Bad Luck

That's the correct part number, but amazon and ebay are full of knockoffs so it could be a bad sensor. Do you still have the old sensor?

I do, suspect you’re gonna suggest tossing it on to see what happens


Sent from my iPhone using Tapatalk

[brillo_76]

Originally Posted by Babyfood1217

I do, suspect you’re gonna suggest tossing it on to see what happens


Sent from my iPhone using Tapatalk

That's what I would do. As you really gotta watch Amazon and ebay sadly.



Sent from my SM-A505U using Tapatalk

[diverscale]

I said that because I had pulsating RPM's when in closed loop (You'll see that you don't have pulsation in WOT) and my problem was my first O2 sensor, without a check engine. And that first o2 sensor is an air fuel ratio sensor. got it from Rock Auto not from amazon, it's too risky.

[brillo_76]

Originally Posted by diverscale

I said that because I had pulsating RPM's when in closed loop (You'll see that you don't have pulsation in WOT) and my problem was my first O2 sensor, without a check engine. And that first o2 sensor is an air fuel ratio sensor. got it from Rock Auto not from amazon, it's too risky.

Good to know you seen this pulsing before. I always pull my o2 sensors from Rock Auto. Always had great success.

Sent from my SM-A505U using Tapatalk