Hi Jim,
![](./images/smilies/spacer.gif)
You are most welcome!
Yes, these sensors go out of spec over time.
![](./images/smilies/spacer.gif)
Slowly, but surely.
![](./images/smilies/spacer.gif)
I had an overheating problem few years ago as my radiator sensor drifted out of spec.
![](./images/smilies/spacer.gif)
It was still changing its resistance versus temperature, but ended up being out of range for the controlling electronics
![](./images/smilies/spacer.gif)
(A/C amplifier)
![](./images/smilies/spacer.gif)
(<- only applies to cars with AC.
![](./images/smilies/spacer.gif)
Non AC cars have a switch instead of sensor)
![](./images/smilies/spacer.gif)
Good practice to get a baseline measurement at lets say 20C in the summer with multimeter of the critical sensors and check them occasionally.
![](./images/smilies/spacer.gif)
Once a year or once every 2 years.
![](./images/smilies/spacer.gif)
Aftermarket cats are usually sport/hi flow and so on, which means they have less meat in them.
![](./images/smilies/spacer.gif)
Good for performance, worse for emissions.
![](./images/smilies/spacer.gif)
Probably the best emissions are with OEM units, but AFAIK even with those are not a walk in the park to get ok emission values for the tests.
![](./images/smilies/spacer.gif)
My car always spends the most time at emission test.
![](./images/smilies/spacer.gif)
It was the same with OE CAT, and the same with my XS Power Hi-Flow CAT/Downpipe.
![](./images/smilies/spacer.gif)
I only failed once at emission test and that was because of an inpatient inspector.
![](./images/smilies/spacer.gif)
Nice inspectors who appreciate the car will spend time revving the engine until and acceptable value appears on their screen and then press the register button.
![](./images/smilies/spacer.gif)
At the last test, the tester spent well over 5 minutes to get my high idle CO right.
![](./images/smilies/spacer.gif)
Nice guy.
![](./images/smilies/spacer.gif)
I always thank them for taking the effort.
![](./images/smilies/spacer.gif)
Ended up at 0.29 vol%.
![](./images/smilies/spacer.gif)
Failure is above 0.30 vol%.
![](./images/smilies/spacer.gif)
I asked him, he said its normal with these cars from the 90s.
![](./images/smilies/spacer.gif)
I don't usually go to events, but who knows what the future brings.
![](./images/smilies/spacer.gif)
Kindest regards and Happy New Year!