I have 06 G35 sedan 6mt. Ok everything started at starting to use the fuel additives. For begginning (Ialways use premium fuel) the car run well, it really revved strongly but then I had using I guess low quality fuel and car did not accel. at all so I started using fuel additives and here my problems started. One time I noticed terrible smell of gas or some additives gas mixture I was then outside of car near gas tank. Also during acceleration I started to hear such knocking sound- it is very dangerous to pistons also.So I had to drive slowly.Also the spoled egg smell cgame to cabin of car during driving that means the ceramic of cat. conv. is milting due to wrong air/fuel mixture. I want to add never the time engine service light(SES) has come on on display.
Then the mixture of air fuel ratio went bad and the additives destroyed my spark plugs 02 sensors(all 4) and also cat. converters. Si I repl. spark plugs 02 sensors and the knocking seemed to go away for a while but knocking came back and now I have new cat. conv. Magnaflow( I ordered accedently 49 state cat. conv. but I have california version-flanges are different)so the local workshop had to redo the 49 state version to california version. Ok it was done. But still the smell of gas is inside cabin and mixture is too rich cause my cat conv. went red from near the rear 02 sensors . So the mixture is still wrong and it can destroy the cats. again if not find out why mixture is too rich and fuel consmpt. is also high and it is not having enough power. Is it sure that it is the front 02 sensors or something else. What about the fuel pressure regulator.

 

GOD.... i couldn't read ANYTHING from that post.

If your engine is KNOCKING.... I think its cooked, you have a Rev-Up motor, so check your oil levels and get someone to put a scanner on it to see what codes you have.

 

No error codes. checked?

 

First off, don't use fuel additives. They don't really do anything. Stick with name-brand gas stations and you should be ok. Stay away from Joe Blow's discount gas, but other than that, all gas is pretty much the same.

Secondly, are you just assuming the air/fuel mix is off due to all these problems? The check engine light has not popped off once?

You should hook a code reader up that does live data and actually look at your short term and long term fuel trims to see if you are going lean or rich. Should be +- 10% from stoich.

If your knocking is detonation, I find it hard to believe you are not getting a CEL from all this, especially if your cats are clogging or you are running lean enough to make them glow cherry red.

 

Check engine light has not popped off even at once! I have checked with code reader also and no error codes, to me it is also hard to believe, I have been several workshops and they are also clueless! But I have read that back 2005 several g35 owners had also same issue with detonation, seems like factory quality failure.

 

My car oil level is ok. I just changed the oil and oil filter.

 

Any modifications to the car? What spark plugs did you install?

 

Car has NGK Platinum spark plugs, washable AEM panel filter, magnaflow cat. conv. Tanabe Y-pipe.