Guys i know this fourm is for G37 but thought i might get some help here...

am having this problem driving me crazy....when i drive the car while the engine temp. Is cold its driving perfectly but once its reaches normal temp i face huge engine power loss its like am driving the car with one cylinder missing the car feels heavy the throttle feels not responsive and stupid and its like on limp mode but without the speed and trans limits ... no CEL light nothing .. i replaced both throttle bodies and maf sensor still the same...took the car to the dealer stealer for major service rlaced spark plugs and they checked compresion and its fine .. the only mod i have is berks HFC and am sure the driver side one died is it related to it.?*Ive done alot of research abt this problem but it made more confused as it may be related to many things like bad temp sensor or bad cam shaft or cranckshaft sensor or O2 sensor i dont know where to start !!!One more thing when i put the gear into drive from P or N the car shakes and the rpm drops for a second then goes back normal but then it stays @500 or 450 which is very low when i compare it to my frineds cars...Sorry for this long story but the problem is making soooo fraustaed and makes me hate me carYour help guys would be very appreciated

 

So what car is this for again?

Btw what you mean by your "hfc died"?

 

Check engine codes. There may be a code without a CEL.

 

Its 2008 G35 Sedan Journey
What i meant is that my Driver side hfc is blown making my exhaust rattles like ****.

Dealer checked with their scanner Found nothing !

 

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Does knock indication/timing retard show up in the generic OBD profile --- using something like torque?

 

Didn't use torque before. I use cipher for logging and there's no option to log knock retard degrees .

 

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So read some threads about this power loss and from what i understand its all related to ignition timing retarding..... so what happens is when the ECU detects any pinging or knocking or even gets a wrong reading from a sensor like the O2 sensor it will go back to some kind of a safe mode where it will retard the ignition and will make the car run lean to prevent any danege to the engine through a Knock Sensor.... so now i guess my problem is 2 sensors the Knock sensor or the O2 sensor ... i have no problem with replacing both but guys any idea what else can cause engine pinging or knocking besides plugs which i replaced them last month at the dealer ...
Btw those sensors are not cheap to replace as the can go for 1000 $ for all !

 

OP, if the cat is damaged, that is your problem! If any sensor failed, it should give you cel.

 

True.

But OP, How did you know the cat is damaged, did you remove & inspect it ?, Maybe it's rattling because of a bad install.

Put the car in P or N, Build some back pressure by revving the engine for a few seconds at about 2500 rpm then start revving and see if it goes beyond 5K rpm freely.

A good test also is to use a vacuum gauge attached to the intake manifold to see if you have any back pressure.

Don't start replacing sensors blindly, Take it to an exhaust shop, inspect the cats & make sure it's installed correctly & there's no rattle.

 

Come back with answers for God's sake !!!

 

Was wondering if you fixed this and if so wjat you did to fix. I have a similar situation where i bought invidia hfc and i went for a uprev tune and they said my car was knocking so they couldnt tune it. Then we replaced the knock sensors and it didnt work. So any help would do. Thanks