My 2004 G35 A/T has not been running like I assume a G35 should run for a couple of months now. There is a huge lag in the car and it hesitates to accelerate. I've looked at possibly every thread related to this and here is what I have done:
1. Brand new Amsoil Filter
2. Cleaned MAF sensor
3. Cleaned Throttle Body
4. Seafoamed through Brake Booster and gas tank
5. New Spark Plugs
6. Techron Concentrate Plus
7. Checked for vacuum leaks and replaced my torn rubber hose that connects to the throttle body
8. I also reset the ECU, Idle Air volume learning, accelerator pedal release position learning and throttle valve closed position learning.

I also have the plenum spacer, Rev-Up Airbox and Z-Tube. After my throttle body cleaning I can accelerate from lets say 20 to 60 and let go of the throttle and the car will remain in the 3rpms for a couple of seconds and then drop down to where it should be with a jerk of course.
*For the hell of it I decided to see what I could get from 0-60 and did 7.35 sec. I almost opened up Craigslist and offered to do a trade with the first car I saw. With that said, does anyone know the possible problem or any advice before I head to the stealership?

 

Does your car sound funny? Could be plugged up catalytic converters in your exhaust system.

How's your fuel economy been? Is the check engine light on?

 

Thinking back it somewhat sounds funny but seems to have lost that exotic note most definitely. But I average around 210-250 miles a tank (another problem). And the check engine light only came on after I cleaned the throttle body without doing the reset. Hopefully the main reason is the catalytic converter is backed up.

 

Plugged cats was my first thought based on your symptoms. New cats aren't cheap, just so you know. There's a plethora of precious metals inside of those things so they cost a pretty penny when it comes time to replace. If you do replace them, you might want to consider getting High Flow Cat replacements since our stock cats are one of the biggest restrictions in the system. You should have pulled the CEL code before just clearing it, to see what it was just in case it was actually a legit problem.

Has the CEL light come back on since clearing it last? If not, how long has it been off for since you last cleared it? (approximate miles/days)

 

Yeah, I should have went to Autozone to make sure it wasn't anything important. And I wanted to get high flow cats but my underbody is rusted to hell. Would they be able to just cut the oem off and weld on some Fast Intentions? And it hasn't came back on since and it's been off since Saturday for about 55 miles

 

The rust won't be a problem. Anyone who knows their way around exhaust work won't spend time trying to get the old bolts off of the cats or any rusted pipe junction.... you just take a cutting wheel on an angle grinder and slice off the ends of the bolts and pop them out with a punch, put in your new components and new gaskets, and reconnect them with replacement bolts and replacement hangers (if need be).

Cats don't usually weld on... they usually bolt on. Welding would be a huge rust/leak problem and make it a fiasco for replacing the parts connected to them.

 

Real possibility that its clogged cats. You wanna get that taken care of fairly quickly tho, cuz when cats are clogged, yer O2 sensors get clogged and then other componants and it turns an expensive project into a down right nasty one. Awful mileage is also a sign of worn O2 sensors.

 

I made an appointment for next week to have them look at my cats. It's at one of the two muffler shops I always go to were the ones that turned me down when I wanted to get my HR-Y Pipe installed saying it will do more harm than good. If all goes well I'll end up getting either FI Resonated Test Pipes or Strup Test Pipes instead of High Flow Cats!

Thanks for that information! I'm at 92,3xx miles now and you are definitely right. I'd rather replace now than be an emotional wreck hundreds of dollars later.

And I really do appreciate the responses! I'll post an update after I visit both shops with hopefully good news!

 

Keep us updated, I'm curious to see what your outcome is as well, good luck

 

Sorry guys I've been caught up with school. But I went over today and the guy said it is doable for $150. On top of that, he had Megan catalytic converters with less than 200 miles from another G35 that he'd sell me for $250 and install for $400. I did some research and it seems that Berk or Fast Intentions High Flow Cats are the best quality or even better, going the test pipe route is cheaper and proves better performance. Any suggestions?