HC ppm 15mph limit 55....reading 67...25mph limit 60...reading 155, NO ppm @ 25mph limit 700 reading 1268... had worse results before with same failing ****...my car does smell of gas pretty good sometimes worse than outhers...can this be a bad Cat.?


here is the list of what I did prior to new failing...cleaned egr valve...rebuilt the throttle body, new sparks..wires...dist. cap. rotor and coil...replaced pcv valve and cleaned pcv tubing... any ideas before I try I new Cat?

any ideas on what causes HC and NO to be about double the limit at same time?

 

mine had almost the same readings when I went, did all the stuff you did and then replaced the coolant temp sensor - the one the computer uses to determine it's air/fuel ratio not the guage sender and the O2 sensor. My car ran fine before this and had no other issues so many here suggested those 2 items and it worked!

Now your car is has a mas airflow sensor compared to my MAF but I think the CTS still performs the same function and the O2 sensors are the same I think as well.

I did not replace my cat since I knew it was good when I had it off and my air injection system seems to test out fine.

Cost me about $10 at autozone for the CTS and $20 for the O2 (cheaper than I expected). When I checked my CTS it still worked but it's readings were off and that must have been throwing off the computer. The O2 was really dirty and full of crud.

I would not replace the cat until you check the other systems first. The car should be running well, good idle, no hesitation etc but just failing emmisions - if it fits that description try the CTS / O2 and it may help.

 

Thanks I got no time, I need it passed now Im bound to get pulled over... I just brought it in to a shop.. I will post results when I get them.