Hey guys I'm new to this site and recently purchased a 2008 g37 coupe. I noticed there was a ton of hesitation when mashing the pedal, so I took it to the dealership. I've heard people fix it by cleaning the MAF sensor and throttle bodies but I wanted to get it checked anyway. They ended up quoting me 4k for a new transmission valve body, radiator cooling fan (always stays on apparently), and a front-wheel bearing replacement??? I also did notice the transmission being jerky sometimes but I'm assuming that's normal for an older car. I've also been recommended grounding kits to help with throttle latency. The previous owner drove it like a grandma so would resetting the ECU help? Should I take it to an independent mechanic and get them to take a look at it? I don't know how hard it is to fix these issues or if they even have anything to do with my hesitation but guys please help. Thanks

 

What I would do is reset the ECU then do a idle relearn. Then if you still have trouble take it somewhere else that isn't a dealer for a 2nd opinion. Find someone on google with above 4.5 stars for a start but this isn't a end all indicator of honesty. When you take it don't tell them anything about your trip to the dealer.

If you can't change these parts yourself you will have to pay someone to do it so the idea is to find someone who won't rip you off doing it. The dealer will rip your face off.

 

You have the 5AT or 7AT? The transmission adapts to your driving style. If the previous owner drove conservatively, their inputs are going to take awhile to be forgotten unless you do a reset. Try the pedal dance for the reset and the throttle/idle relearn procedure as well. Don't waste time with the grounding kit; it won't help. I was a believer in that as well but a member proved that the signal is basically a standalone/isolated unit and a grounding kit will have no effect. You can take it a bit further and replace the airbox filters and clean the MAFs.

The dealership isn't going to diagnose and repair anything. They're just going to throw parts at the problem until it's resolved; at your expense. As for the wheel bearing, are you noticing any odd noises from that side of the car? Would sound like a droning/flat tire like sound if the bearing is bad.

 

You said the previous owner "drove it like a grandma," were there any maintenance records? Repair receipts? Did you have a pre-purchase inspection done? When you are driving does the engine rev past 2500RPM (hesitation or "Limp Mode")? Not trying to beat you up, but... Here is what I suggest:

1] Check for any codes
2] Reset the ECU
3) If you are able, clean the throttle bodies
4) The Idle Relearn procedure is a PITA to do, but sometimes is needed.
5) Change the transmission fluid
3) If problem persists get a 2nd opinion from a independent shop that, preferably, specializes in Nissan.

The 5AT transmission is pretty rock solid. Unless grandma lied and drove the hell out of it you should not be having any problems. Not to say you can't. Again, a check of the codes might help. Front wheel bearing replacement is pretty straight forward. Again, if you are able you can easily replace them yourself. The cooling fans are another issue that may or may not have a simple solution. Further diagnosis would be needed.

Keep in mind, there is a difference between hesitation and the car going into limp mode. If the engine will not rev past 2500rpm, then there is a more, potentially serious, issue going on.

And for the record, my grandmother was a speed demon. She could shift gears on her old Alfa Romeo faster than most and flew down the expressway. Not all grandparents are turtles...

 

I have the 5AT. I got the filters replaced last week and there wasn't a noticeable difference. My car doesn't idle badly or anything, so I have no idea if cleaning the throttle bodies is worth the risk since a lot of people has had issues cleaning them. Also there wheel bearing is silent not a single sound comes from it so i dont know why they'd want me to replace it.

 

Haha, your grandma sounded fun. I don't get a single noise coming from the bearing so I'm not sure if I should replace it. Also, it doesn't go into limp mode. Once it starts going it keeps going after the 3-5 second delay of hitting the gas pedal. I found out the cooling fan is actually a simple 40 dollar relay module that takes about 10 minutes to replace, so I'm going to do that myself. I don't know if that fan would even fix any of the issues but ill do it anyway. Funny how they're charging 300 bucks for that one.

 

Your car is 2008 with unknown mileage and almost certainly have never been serviced. CLEAN the throttle bodies. I can guarantee that are full of muck. As long as you follow the guide you should be fine. From the sound of it I think you are in better shape than it appears. It seems the car just needs some general maintenance.

As far as Granny is concerned, she's 98 and going strong- though her speed demon days are far behind her...

 

glad to know your granny is going strong. Ah forgot to mention. The car has 131k miles. I also do have the service records and it seems like all maintenance was done. I was afraid the dealer was just throwing the replacement cost for the transmission valve body because they didn't know the issue and wanted me to just replace the part. The car idles just fine but yeah I'm assuming they're dirty too. When I do clean them, is it bad to touch the valve? Some people swear against it and some others say it'll do no harm.

 

Some say yes, others say no. That debate has been going on since who knows when and everybody has their own opinions and, ultimately, will do things their way.

I never had any issues and I slightly move the butterfly valve. Full disclosure though, I remove the entire throttle body from the intake manifold (4 hex bolts) and clean the backside of the butterfly that way. I do it this way because I replace the o-ring (gasket) as part of the cleaning. It might be overkill but it works for me.

At 131K they are seriously overdue. As RMB5190 stated, the stealership is only going to throw parts at it (or annoy the hell out of you to trade for something new).

 

im assuming I should probably clean the throttle bodies and maf first and then the ecu reset and idle relearn and all that. I’m assuming you’re referring to the that cleaning being overdue. Most of the people that resulted with better performance after doing the cleaning previously had bad idling. I don’t have any idling issues. So would it still help then

 

Cleaning the TB's will not hurt. Here is what I would do:

1) disconnect battery;
2) clean throttle bodies;
3) clean MAF's (I don't);
4) after all done reconnect battery (ECU will have reset)

When you first start the engine see how it acts. If the engine idles high/ does not go down/ or acts erratic- then perform the IDLE RELEARN procedure. If the engine idle acts normal, drive the car for a while. In other words, DO NOT automatically perform the IDLE RELEARN procedure- it may not be necessary.

 

Ah so I don’t have to wait a whole day for the ecu to reset. I’ve heard people say you have to disconnect it overnight and leave it for it to reset.

 

No. A few minutes is all it takes. Usually 10-15min. or longer will suffice. By the time you're done cleaning the ECU will have reset itself.

 

Are there any signs or ways to tell if it reset

 

It should drive like a bat out of hell.