Sadly, my 235K ES300 failed smog test, high HC fail at 15 and 25, by 20 PPM each test. Local indy Lexus shop sez both cats need replacement; that’s not happening.

Poking around here, some folks say ECU caps can be changed out, not going to do that. Some others say engine coolant temp sensor can trigger the ECU as well; strangely I have a new one I can pop in. I will say I was surprised how strongly I can smell gas fumes when standing by the rear of the idling car.

It failed smog 2 years ago as well; new charcoal canister and the 3 sensors by the intake manifold cured that.

Not doubting the indy shop, but any other BTDTs before I sell it to the state? It’s served me exceptionally well for 25 years, but if I can eek out another two years, in the current car-buying situation, I will spend some time on it.

I appreciate any thoughts.

 

where does this vacuum line attach too?

 

Hello,

Impossible to say anything without first seeing the Engine Live Data, it would be a definitive way of telling what the issue is. Get an OBD2 Scan Tool, with the Engine at Idle and the Shifter in Park, access All the Live Parameter your Scan Tool would allow and post them here. If your Scan Tool is capable of Plotting the Data on the Graph, select just the Bank 1 Sensor 2 (B1S2) Sensor Alone, and let the Graph get built up for a while, then post its snapshot here too.

Thaat looks like a Temperature Sensor Pigtail..

Hope this helps and best of luck!

 

Please upload the smog check vehicle inspection report, and more importantly, the vehicle's 5 gas reading (HC, CO, O2, CO2 and NOX) at 15 and 25mph.

Let's see if I'm able to help you to pass the smog check this year with minimal repair. Make sure the vehicle is free from vacuum and/or exhaust leaks before the CAT.

Two years from now your vehicle might no longer need a tail pipe and dynamometer smog check. 1996 to 1999 model year vehicles are transitioning over to the OBD-only smog check, which is a much easier test to pass.

https://www.bar.ca.gov/arsc/newslett...lations-update

 

This is your vehicle Pass/Fail standards, so your HC reading at 15mph = 71ppm and 25mph = 55ppm. I still need CO, NOx, O2 and CO2 reading.

 

Thank you for the responses so far. Here are the smog test results:

 

Your air fuel mixture ratio was 14.64 parts of air to 1 part of fuel, and that indicates the vehicle is running rich. That's why there was a strong fume coming from the back of the vehicle.

These are the following areas that can cause a rich air fuel mixture: mass air flow sensor, oxygen sensor, fuel pressure regulator, spark plugs, coolant temp sensor and intake air temp sensor.

If you are mechanically inclined and handy, then you can check those mentioned above. If you're not, it's best to take it to another shop for a proper diagnosis. If the first thing a shop recommends is replacing the catalytic converters, then you need to run away as fast as you can.

 

The thing is that cars already have all the tools to check the Air/Fuel Mixture already built-in, all you need is to access the Engine Live Data, it will show you how much the ECU has to Correct for the Mixture Imbalance, and it will also show what Data the ECU gets from all the Sensors, making it very easy to see whether the Mixture is Lean or Rich, and what the ECU does to Correct it one way or the other. Rich Mixture is usually quite rare, not a whole lot can cause it, at least compared to the Lean Mixture, so there is probably a good reason for it. Again, a Scan Tool will go a long way to make this issue easier to diagnose.

Hope this helps and best of luck!

 

Thanks for the responses, I appreciate it. I’ll try and get the live data next weekend. I have an old Autel scanner, so we shall see!