If I had a cat to cook, I’d understand, but it magically disappeared like my ex wife’s faithfulness.
It’s the tbi rich smell I’ve smelled from every tbi truck I’ve seen.
Time to acknowledge an inconvenient (to some folks) truth:
Rich "smell" does not always indicate an actual rich mixture.
ALL engines push hydrocarbon emissions into the exhaust manifold, and from there downstream. That's WHY there's a catalyst--to reduce the HC emissions into water vapor and CO2.
No catalyst, or a failing catalyst = more HC emissions than folks are used to. Which makes them think the engine is "too rich".
WHAT DOES THE OXYGEN SENSOR SAY?
Assuming the O2 sensor is working properly, that is the judge of "too rich" or "too lean".
No catalyst?
Of course it "smells rich". And if you're getting that smell from other TBI vehicles, all I can say is that the newest of them is twenty-plus years old, they've probably got failing catalysts, too.
had this recently on a friends "de-cated" truck. the thermostat was stuck open so the engine would never get up to temp. smelled real gassy.
Absolutely. A failing CTS that shows too-low temperature, or a failed thermostat that causes too-low temperatures can drive the mixture pig-rich, set codes, cause all sorts of trouble...
i'd also look at replacing the CTS, it is almost a tuneup thing like a 3 wire o2....
...but on the whole, I'd rather have a functioning OEM CTS than a cheap-junk aftermarket CTS.
In my driveway, if the CTS (and most other sensors) isn't showing a fault, I leave it alone rather than replace it as preventative maintenance. MAF sensors, and O2 sensors are something of an exception to that.