Hey everyone,

Let me explain briefly what happened to me and let me know if you have an idea:

I bought that car:
2004 G35x (AWD) 5AT with 120k miles

1. Had horrible gas mileage (12mpg) so I decided to give it some maintenance
2. Changed air filter & oil change, but still bad (but better) gas mileage
3. Changed spark plugs AND did a SEAFORM at the same time and the problems started...
4. Cat from the driver side was clogged (real bad because of the seaform) and became RED (hot) while driving, car had difficulty going up hill (no power)
5. Now I have some brand new Kinetix high flow cats but still the SES and no power

Anyone has ideas ? My mechanic tried to reset the ECU but he can't get it to flash (SES light).

I'm running out of ideas and a bit pissed off by this...

The one who can find me the problem will get a PayPal reward as I need this solved FAST.


***UPDATE***
Talked with the mechanic, he told me an oil change has been done after the seafoam.
He also told me he didn't notice if the tranny changed speed while driving as the engine seemed to have difficulty getting power (he couldn't drive at a normal speed).
He guesses it could be the O2 sensors... could he be right ?

***UPDATE 2, GOOD AND BAD***
Hey guys,

To give an update, we changed the cats (one was very clogged) and the problem was solved, I've had good mileage but still a SES light (even after resetting ECU).

I drove for a good 600 miles and didn't have any problems (except a grinding noise from exhaust at ~2-3000 rpm when not accelerating too fast), but exhaust is in bad shape, so I don't mind much.

Car ran fine for a few days after high flow cats were installed. Now, this morning, got a SES light on + flashing and couldn't leave my parking... tried to press gas pedal on P, but it wouldn't go over 3000 RPM.

I had an OBD2 scanner to find these codes when the car ran fine: (2 days ago): P1168 and P1051.

Anyone can help me out ?

*** 4th UPDATE ***
So we did some tests and we started the car with the MAF sensor unplugged. Boy it did run smooth. Idles perfectly but with lots of lights in the dash. Looks like this could be the faulty thing ?

So we tried 2 and 3 times, when the MAF sensor is plugged, the car idles real bad and wants to die. When it's unplugged, it gets a great idle and sounds good.

Question is... can I drive with the MAF sensor unplugged or it'll make the car to shut down ?

*** 5th UPDATE ***

Compression test has been done and the engine is in awesome shape (for the 130k mileage on it). So engine is good, now it's the time to find the trouble. O2 sensor from Infiniti = 171$ / 199$,

Garage found out that there's a tube(?) under the air filter that's got a huge crack on it and air was entering from there...this could be the big problem.

 

Pick up some crc MAF sensor cleaner and spray it down. Post SES codes

 

I believe my mechanic cleaned the MAF. Also, I don't think this would cause the car to have a huge loss of power. By huge loss of power I mean I cannot go faster than ~15mph going uphill.

 

Have you got the engine codes read? What are they

 

try the acceleration sensor, had a issue where i would floor the car but it wouldnt go past 40

 

Has it been tuned for the high flow cats?
Tell us code numbers, and is the car revving high or just not going uphill?
Does it downshift?
When I cleaned my throttlebodies the transmission stopped shifting correctly untill I put some miles on it and did a tb reset.

 

Waiting for the codes, should have them tomorrow.

 

Was SES on when the problem happened ?

 

No tuning has ever been done to that car. Last time I tried it (after the sea foam / before new cats), the car would not shift I guess (unless I use the tiptronic).

What is a tb reset ?

 

***UPDATE***
Talked with the mechanic, he told me an oil change has been done after the seafoam.
He also told me he didn't notice if the tranny changed speed while driving as the engine seemed to have difficulty getting power (he couldn't drive at a normal speed).
He guesses it could be the O2 sensors... could he be right ?

 

yes the ses light was on also check your throttlebody make sure its clean some times dirt builds up in there causing it to open up more then it should at idle

 

Is he not reading your engine codes or what? Bad o2 sensors throw an engine code. Call him back and ask for engine codes

 

free at autozone they will tell you what the coes are and we can tell you how to fix them

also tb reset is
throttle body reset, look it up on here.

and yes o2 sensors can be messed up from swapping to high flow cats, or get clogged by seafoam. lots of things can happen and that would make your car get worse mileage

 

+1, it is common for seafoam to clean carbon, which ends up fouling the o2 sensors.

 

Did you go back and check all your connectors to ensure you reconnected them tightly after the spark plug replacement. Sounds funny but that was my problem after replacing my plugs. Recheck everything you disconnected, even pull it back off and reseat it. Some connectors you have hear the click. Hope that helps it did for me. Good luck