What's up,

I have an 04 g35 coupe, all stock with about 98k on it. I've owned this car for 5 years now and still love it just running into issues. I had the knock sensor harness replaced yesterday because my car was throwing a code P0327, this solved that issue and I gained a lot of power back while driving. Along with the P0327 code, I was noticing other things that I thought would have been solved with that replacement. My car has trouble starting when it's warm, kind of like the battery didn't have enough power to start the car. I don't believe it's my battery I also have issues when accelerating reaching higher rpms. The issue begins around 4200 rpms where the car just stop pushing and climbs speed at a cruise, the engine sounds like it's trying to perform but no results. So the knock sensor harness fixed the P0327 (BTW got it from z1 motorsport for like 35 dollars, and a intake manifold gasket set for 50, paid 250 to have it fixed). Still facing the other two issues, I'm about to replace my spark plugs just waiting for my engine to cool down a bit since I just got home from work.

Any opinions or advice at where to begin would be a great help, trying to have it drive like it did 5 years ago.

Recent maintenance,
-oil change (full synthetic) every 5-6k
-only premium gas
-MAF sensor cleaning (500 miles)
-new K&N air filter (500 miles)
-Transmission fluid checked
-spark plugs

Thanks!

 

Warm start problems might be a failing starter, does it start sluggishly or doe sit just fail to start (audible click or no sound). The starter solenoid is succeptible to heat soak and when they're near the end of their life hot start problems begin to manifest. It's almost impossible to troubleshoot as well since the time it takes to remove the starter gives it enough time to cool down and it works just fine on a bench...

As for the engine power issues, get an obd2 scanner that can deliver real-time information and watch the sensors. I highly recommend a bluetooth OBD2 adaptor (I use a BAF X one from Amazon, ~$23) and the smartphone software Torque Pro ($5.99 google play store). You can set up data logging for whichever sensors you prefer and it graphs the data, easy to reproduce the issue and go over the graphed logs when you get home. Check for ignition timing, upstream O2, etc.

Also take a can of throttle body cleaner and spray the intake tract anywhere that it could be sucking air, make sure you don't have a vacuum leak somewhere.

Also do a ECU, Idle , Throttle recalibration, use a timer, it needs to be performed very precisely for it to actually recal. Your computer probably has a lot of bad habits stored up from that bad knock sensor signal.

http://www.nicoclub.com/archives/g35...-learning.html

 

Definitely going to look into trying to recalibrate everything definitely has stored information for driving patterns, I have a obd2 scanner car throws no codes and all sensors seem to be fine, I did just change my spark plugs where I discovered a lot about my car.
1.) spark plugs were shot
2.) the driver and passenger side 3rd ignition coil's are shot which is what I believe is causing the power loss and starting issues,
3.) there was also oil covering the old spark plugs in the slots with bad ignition coils,

I order new ignition coils with overnight shipping I'm going to install them tomorrow and hopefully it solves these issues.

Pray for my G!

P.S. took the car for a cruise around the block with the bad ignition coils and it seemed to drive fine, I actually gained a lot of power back just from the spark plug change. I did receive a burning oil or gas smell which I think is the residue from the oil getting into the spark plugs.

 

How much oil exactly was in the wells? Was it enough to cover the sparkplug or just a little bit at the bottom around near the hex socket? The valve cover O-ring seals around the spark plug wells need to be replaced (as well as the valve cover gasket once it's removed) if it's bad or you will just run into this problem again Soon™

 

They were both about covered on majority of the thread, and the ignition coils were covered in oil, I saw somewhere else that it may be the o-ring and valve cover gasket, any idea on how much those repairs would cost. and you think it's safe to drive to work tomorrow with somewhat bad ignition coils? obviously it isn't good but I have about a 20 minute ride to and from work. the car only has about 98k on it and drives smooth so I don't think it would be anything past the gaskets being cracked.

 

Probably fine just dont get aggressive with it, the o-rings are cheap, the valve cover gasket as well, ordered online you can get everything for under $50 if you have a short budget. Intake gaskets are metal and re-usable so that's not an issue but you need to remove the plenum to get the valve covers off. Troubleshoot the ignition coils for resistance (ohms) if any are bad replace them as well, they're a bit more spendy at $50 a pop for the cheapest option but pretty critical to the engine actually performing so....

 

any chance the oil in the spark plug well is caused by the spark plugs not being tightened enough, when I was unscrewing the old ones I really didn't have to use any type of strength to break the initial seal. Just trying to get all the probabilities out before I pay someone 300 bucks to replace my valve cover gasket and o-ring.

 

No, because there's no oil in the combustion chamber that the spark plugs goes into the o-rings are a common point of failure unfortunately. At least you can get aftermarket o rings now, I heard there used to be no replacement ones ( (no oem ones anyways) and folks used to have to replace the entire valve cover...

 

thanks im gonna replace my bad ignition coils today and try to make an appointment for Saturday to have the valve gasket and o ring fixed. Think I could just replace the 2 that have the leak or might as well replace all of them since the o rings aren't to expensive?

 

That depends, if you're only leaking on one bank then probably just do that side since it sounds like you're paying a mechanic to do it. If it was me I'd do both just because... but it would be cheaper since I wouldn't be paying someone so...

If you're leaking on both banks then definitely replace everything.

 

both the driver and passenger side closest to the cabin have oil in the spark plug wells so looks like I'm gonna do everything, would love to attempt to do this to my car I do a lot of work myself but haven't done something like this before so I don't want to mess something up trying to fix the problem.