I've had my g37s for about 3 years now and it seems to be getting slower. I've put about 35k miles on in that time and am around 67k. I've got the 7AT and had the dealer update the software. Didn't really help. I notice stumbling on acceleration and rough shifts up and down when in auto mode. Also my gas milege seems to be getting worse. I was getting 20-21 mpg and now only get around 17 mpg. I drive probably a 50/50 mix of highway and city. Tires are brand new with the correct pressure. Any suggestions?

 

Not sure whats been done mods/maintenance wise but here are a few places to start:

- Clean (and oil if applicable)/replace Air Filters. -- I cleaned and oiled mine last week (K&N), while they didn't look to bad I noticed a bit cleaner, smoother acceleration after they were cleaned. Waiting to get through a tank of gas to see if MPG has improved.

- Transfer Case & Diff oil changes --- I've heard good things about these done as combo especially in terms of stop and go in the G. Relatively easy DIY's as well -- I have these in the queue for next month once I have a garage again.

-ECU Reset --- I'm also in a 7at (X Sedan) and had the update, it works for a while but gradually defaults back to feeling like I'm towing a boat around. I reset my ECU about once a week and drive it hard right after. This is more of a band aid because it does wear off after a while, but it helps none the less.

-Tire Pressure --- Obvious one here and already mentioned, enough said.

Lastly, realizing that its summer and that engines and heat don't play nice. Not sure where you are from but we have had some hot humid days this year and I notice a significant loss in power when driving in those conditions.

If all else fails, Slap a NOS sticker on the car that should net you a minimum of 100 HP....

 

Throttle body cleaning? Maybe o2 sensors are slow to respond (signs of old age).

 

Forgot to mention I've checked cleaned thottle body several times. Didn't help. I guess I could have the dealer check the o2's. Have a few other issues they could address too.

 

Have YOU gained any weight recently? LoL

I think Tbau has the right course of action. If you haven't had it serviced at 60K I would suggest it. I just did mine and my car drives so much smoother than it did. Before I thought it was fine, but I had acceleration stumble as well, slightly hard shifts (6spd tho) and a couple other issues. That service cleared it up for me. Give it a shot

 

Whats the 60k service. Oil is just about due but I do that myself. Air filters were done at 55k.

 

clean MAF sensors?

run a bottle of Techron concentrate in it - i run the gas tank down to close to empty, pour in the Techron, let it idle a few minutes. then drive to gas station and fill up. may need to do this for a few tanks if you've never done any thing to clean the fuel injectors. Techron concentrate is recommended by Porsche, so you know its good.

 

Did an oil change, differential flush and new fluids, injectors serviced (cleaned), checked all belts, trans flush and new fluids and some other things. But with regards to how it drives...thats stuff was the important mentions. I truly noticed a difference.

 

doesn't hurt to run some fuel cleaner as well. My MPG has hit rock bottom I remember filling up the tank and getting like 350 now I fill up and I get under 300...


eventually it could be your spark plugs too but your mileage doesn't warrant that

 

Yes! Fill your tank on or near an Interstate Highway. Set odometer A to zero. Drive 350-400 miles at or slightly above the speed limit no cruise control.

Refill tank at the 1/4 mark or slightly below. Divide total miles traveled by the number of gallons to refill tank.
This is the only accurate way to measure MPG

Report back

You may be surprised to learn there is probably nothing wrong with your vehicle

Telcoman

 

More like the way to get "inflated" MPG's. lol

Real world numbers = real world driving. Not driving on the highway on cruise control to inflate your mpg.

 

Real world mpg after my 4xx mile cruise last sunday.
Calculating mpg the old fashion way I got 25.9 mpg.

This included plenty of hwy miles but also lots and lots of backroads, corners and elevation changes using gears 3-5.

 

Resetting the ECU;

 

... Bumblebee tuna

 

Hey did you do the service yourself or what shop did you take it to? Mine just hit 55k and I'm also in santa rosa so not sure where a good place to go is.