Pre-catalytic converter problems

[jmb275]

I have a bit of a lengthy story and would like some advice. I have a 2000 Infiniti I30 with 73,000 miles that has been very well cared for.

Upon driving home from Yosemite National Park there is a very steep (read 16%) grade I went down. I then stopped at an ARCO gas station (first gas station I saw, and I needed gas) and got about 2 gallons of gas. I NEVER use ARCO gas but I needed it. A few miles down the road and the Service Engine Soon light comes on. I plug in my OBD II code reader when I get home and read a P0420. I then found out there is a ECM upgrade and that this is a common problem on the Infiniti I30.

So I take it to the Pleasanton, CA Infiniti dealer and I told them the code, and that I wanted to know their full diagnosis and whether or not I had the updated ECM (for $145 diagnostic fee). They respond with a P0420 code and that both the left and right pre-cats need replaced along with the O2 sensor and front tube assembly for $3000. They also showed me some print-out of some sort of air-flow test they ran confirming the pre-cats were "weak". Of course, my 8year/80,000 miles warranty was up in November. Well I can't afford that kind of a repair so I didn't have it fixed.

A few days later the SES light goes off. I can't afford those kind of repairs so it's now been a month and I haven't seen any difference. The SES light isn't on, the car seems to be performing just fine.

My question is, is it possible that I had some unburned gas make it down to the pre-cat when I was going down the steep grade, or that I had a bit of bad gas that caused the cat to act up? And if either of these things happened, is it possible that the pre-cats are still okay?

[allensteiner]

i think your car might've gotten confused due to a huge diference in elevations through the park ( between 2 and 13k feet ) and probably just misinterpreted signals caused by air density. it's a fuel injected motor so fuel should not flow where ever it want's to go, even if the car was upside down. clear the code and see if it comes back.

[Mike G]

First off, welcome aboard and visit often...

Secondly, don't sweat it. My car will toss that code every time I go cheap and buy the low grade fuel (we have 85 octane here). I will usually follow up by adding a can of octane booster to the low grade gas and fill up with the good stuff the next time around. Off goes the light. If you ask me, these systems are more sensitive than a teen-age girl.--Mike

[jmb275]

Thank you very much for the help. $3000 for emissions parts is just insane. I mean I care about the environment and pollution and all, but COME ON. Anyway, I think I'll wait it out and see if the light ever comes back on.

Thanks again!