P0420, not the converter

[jseabolt]

Well Dad finally took his 1998 1500 Express van to the muffler shop as I advised him about a year ago to have the converter checked out. The guy at the shop said it was OK.

 

So apparantly it's not the converter. They cleared the code but it came back on.

 

So let's see. I have done so far:

 

Replaced both front O2 sensors.

Replaced thermostat (because guage seems to indicate 180F instead of 210F)

Tried defouler trick (where you use two no foul sensors and install O2 sensor into them so it throws a fake signal to computer)

Had converter checked. The muffler shop said it was OK.

 

What else could it be? Replace sensor after the converter?

 

The muffler shop said something in the fuel injection could be causing this. I do know that this all started last spring when the distributor cap went bad and was causing 2 cylinders to misfire dumping fuel into the exhaust system. That's why I thought the fuel may have damaged the converter.

[gmtech4]

muffler shops dont diagnose codes ,wrong shop to take it too,,,,

 

you guessed to many times and wasted real diagnostic MONEY !!!!!!!!

 

shame shame ,tisk tisk

 

this is from the code 420...

 

 

6 Before the three-way catalytic converter is replaced, make sure that the following conditions are not present:

 

 

 

• Misfire

 

 

 

 

• High engine oil consumption or coolant consumption

 

 

 

 

• Retarded spark timing or weak spark.

 

wrong shop bud