2006 M46 Catalytic Converter problem

[wenc82]

Hi guys, it is my first time posting on the forum, so just bare with me if I mess something up. I have a 2006 M45 with 100.5 K and last Nov with ~91 K Miles the check engine light came up, went to the dealer, and the dealer said it was the driver side manifold catalytic converter, so got it replaced. Fast forward a few month to january with ~95 K the check engine light came up and it said it was the passenger manifold catalytic, it sucked but replaced it. Now last Friday, I was driving down the highway, all of a sudden the car lost power, so I coasted the car to the shoulder, all the lights on the panel lighted up. I put the car in park, stepped on the brake to turn the car off, but instead the car started, no more lights so I drove back home. On Saturday driving on highway the check engine light came up, so I took the car to autozone to get the code. The guy at autozone said it was the O2 sensors. Took the car to the dealer first thing in the morning, the dealer ran the diagnostic, and said the O2 sensors were fine, but he noticed smoke coming out from where the catalytic converte and the exhaust pipe met. He took off the four bolts, and to his surprise there was no honeycomb in the catalytic converter on the driver side, then he went on to unbolt the one on the passenger side, and half of the comb was gone. The explanation they gave me, was that the engine was running an extremely rich misture thus burning both catalytic converter, but the tech also said, if the mixture was rich and with working O2 sensors, the ECU would have corrected. The other possibility is that I have taken the car somewhere and have the intake cleaned, (which I did not) and the people might have messed it up. I told the dealer that what happened is not right, and i do not want to put in 2 more catalytic converter to then have to deal with the same issue a few month down the road. They agreed that the situation was not normal, but in short, the tech at the infiniti has no clue what is causing it, so I was wondering if anyone at the forum had ran into this problem or have any suggestion or shed some light

Thank you in advance

[atlM35]

Air/Fuel mixture or timing issues can cause this.
Check spark plugs, Primary O2 sensors, Air Filter, and reset ECU to start with.

[svard75]

Sounds about right. I've had the same thing happen to me. The unburned fuel travels down to the HOT cat and ignites there instead. I would check your intake filter and MAF sensor. Do you use a K&N reusable filter with oil? The oil could have contaminated the MAF causing the ECU to dump more fuel into the chamber (Maybe, not sure).

[wenc82]

Thanks for your response guys. No, I use the regular paper filter. I got back from the dealer, and they said that some of the cylinders were not holding the compression, thus causing the gas/ oil to travel to the CAT. With so many sensors one would think that the check engine light would come up sooner (maybe not?). Also the engine seems to be a little pre-mature (~100K) to be having this kind of problem right or is this something expected?

[svard75]

Oh shoot your gasket needs to be changed. Coolant and oil likely leaked down there. That would also burn out the cat. Unfortunately the M45's suffered from this issue more frequently than they should have.

huge-engine-problems-m45-2006-help-t326 ... s#p6271861

[wenc82]

I am taking the car to a buddy's mechanic that work on engine, maybe he can give me a little more detail of what to replace instead of an engine swap. I will post my finding.

Thanks guys.