Peace


I had a couple posts as mikechec9, but aol acct got hacked, so I'm starting over here. So...Hi


I have a couple issues with which I ardently require assistance. The most pertinent has to do with the rough driving engine on my '08 G35S sedan. It started out where the engine would only drive this rough when she needed an oil change at or around 6k miles. I only use full synthetic 0w40 or 5w40 Mobil 1 or Castrol Syntec oil. I only use 91-93 octane Shell, Texaco/Chevron gasoline. And I always change oil just before the 6k mile mark (or I add about 1/4 qt to hold me off for an additional couple hundred miles due to burning).


Then nearing 200k miles (maybe at 160k or so), while most often driving brilliantly and smoothly, she started driving rough at times even after oil changes. The same type of "rough" that the engine exhibits when in need of an oil change. Sometimes it would only start off rough and then become smooth again within about 30min (well after the engine has warmed up). Then the more miles closer to 200k, she would be rough more and more often. It would be completely random. Now, just past 200k, she is rough more often than she drives smoothly.


I changed the air filters. And while that made a considerable difference (because I usually keep those changed), she still drives substantially rougher than her signature butter soft smoothness (pardon my lack of adjectives).


Then I finally noticed a variable: While the engine sometimes drives smoothly when its dry outside, it ALWAYS drives smoothly when I wash her or when it's raining. I mean immediately. And every time.


There are no codes, and the only thing that the dealer says I need is a drive belt, as there is a considerable amount of play in the current one. And I know that the timing is related to the timing chain and not the serpentine belt, but it's really like the timing is off by a couple hairs. Because she's rough, then smooth, then rough again...until she's back on point. Or maybe the O2 sensor is becoming progressively worse? I figured there would be a code for that.


Does anyone have a clue as to what the problem is? I already reset the computer to no avail. Any direction would be exceedingly appreciated.

 

Why have you not changed the belt if you were advised they were in need of replacing?

This is pretty easy to do and Gates belts can be had for about twenty bucks. I'd start there.

 

You are using the incorrect oil
Use 5w30

Telcoman

 

Indeed. I wasn't advised to replace it. In fact, they said that the degree of play in the belt, while measurable, has no effect at all on the vehicle performance so long as it doesn't snap. I researched and I found some that say it does, and still others who say people remove the belt altogether in an effort to gain performance. Of course I deduced that the later is taken out of the context of a newer vehicle with a computer managing everything tied in with the belt.

Nonetheless, I am going to have this replaced anyway. I was just wondering if anyone had a clue how water, or a lack there of, might contribute to a belt with slack causing the engine to be rough. Basically it sounds crazy, and I'm looking for some clarity via a logically sound explanation...be it related to the belt or otherwise.

But I agree, I can certainly address what needs to be changed anyway and take it from there. But in the interim if I can find out the issue, I can have it addressed at the same time I have the belt replaced...in the event that the issue is something besides the belt.

 

Greatly appreciated. Based on my research and experience over the first 160k miles, 40 weight is a better grade oil than 5w30. Can you kindly explain why you think 40 weight is detrimental?

 

Too thick!
Read your owners manual

Telcoman

 

As far as the oil, 40wt isn't what the factory service manual says to use. It probably won't hurt the car if you keep using it especially if you've already made it to 160k (are you the first owner?), but if I were you I'd stick to what the engineers and dealerships recommend as they know better than anyone else. There's a lot of opinions out there on oil but think about who you trust more. On your next oil change, just use what the manual says and hope it solves your issues - although I HIGHLY doubt you'll notice any difference. Also, your engine shouldn't be acting any differently when it "needs" an oil change, unless you've waited WAY too long. If it's acting differently for that reason, it's because of lubrication issues causing additional friction inside the engine. More friction = more heat = permanent engine wear! Think, man!

I've never heard of an issue where the car runs BETTER during bad weather but that doesn't mean anything... If you're sure it's related to the water, have the car running (rough) while you spray it down trying to find the exact location the water needs to get in order to cause it to run properly. When you find the "spot", post it here and we'll be able to tell you what's in that area which might cause problems. TBH, I doubt there's a connection between the water and the car running properly, as water isn't supposed to touch anything that affects engine operation. Usually if it does get in, electronic components start frying and you have bigger problems.

You could probably help people diagnose your issues if you clarified what you meant by "rough" and "smooth". Are you getting RPM fluctuations at idle? Misfires at speed? Or just some weird vibrations you're attributing to the engine? Please be as specific as possible in the future, down to the speeds and RPMs your getting your issue if applicable. At your mileage you might have something else going out causing intermittent vibration such as: worn engine mounts, worn transmission mount, carrier bearing going out, blown out dual mass flywheel, etc etc etc.

Belts are real easy to replace (good DIY learning repair) but it's not your problem either - if it was slipping you'd be having power steering and electrical system issues too as the alternator and P/S pump are attached to the drive belt.

Ok, time to study thermal systems analysis again... procrastination time over xD

 

Probably a problem with the electrical system, getting moisture into the lug/chassis connections is causing a better electrical connection. When it's dry you probably have higher resistance.

Clean up the entire ground system starting at the battery, then clean the positive cable connections, including at the starter.

 

Brilliant. That's gotta be it. Because my second issue was regarding my audio system. That would make sense as to why it also irregularly fluctuates when not wet. There is no corrosion at the battery, but I will track it down and get back to you.

 

Theres a main bonding jumper under the coolant reservoir that goes to the timing cover, don't forget to check and clean the chassis side of the negative battery wire, it's just another 12" jumper wire. The fusuble link on the main battery post has 3 total connections, battery and two on the link itself. Lastly would be the starter.

It's possible you have either a pinhole in the wire itself or perhaps the headers melted a section off of the main starter wire so inspect the ENTIRE length of those wires.

 

This is a possibility. Also, if water is getting into the intake via dense air from rain or the filter getting wet, it will act as though more fuel has been added. I cleaned the intake side by injecting water at the upper plenum. When water is injected, the idle immediately increases just as it would spraying a fuel or other form of injector cleaner. You might have fuel delivery issues.

 

This is why I thought it might be the O2 sensor. Any idea where to start diagnosing fuel delivery? Especially since there is no code tripped?

 

I'd start with what cleric670 wrote above 1st. When a couple door lock actuators went out on me and the hatch started getting sketchy, I went through ALL the oem grounds, removed paint and used dielectric grease. At this time I also added my diy stealth grounding kit. The stereo and transmission did in fact improve but not the actuators. Once I used one of the ebay actuator kits on all 4 doors, my hatch started to open every single time, which prior to this it would work intermittently. Around the same time, my battery terminal, the negative iirc was getting mucho corrosion which was odd because it was never an issue, not in 14-ish years. I got those red/green corrosion inhibitors for the terminals and replaced the terminals and everything was right as rain.
My point is, Nissan didn't do a great job with their grounds. Try the above before or after doing a sea foam or equivalent treatment to flush the injectors. It could be the MAF as well, seeing that it's first in line when it comes to air entering the intake and air density/water has a positive effect. If these things don't work, it's outta my league as I haven't had the issue you're dealing with therefore I haven't attempted to solve it.

 

Thanks so much. I see what they mean by misery loves company

Do you by chance have any schematics of the OEM grounds? Or is it in one of the stickies and just not labeled as such? If not I can just trace it.

I will also address the MAF. But I'm leaning toward the ground, as one of my amps is giving me similar "scratch my head, am I the first in the world to have this happen" problems. I'm being a trooper about it, but this car--which still looks brand new--is really driving me next to crazy.

 

http://www.nicoclub.com/FSM/G35/Sedan/2008/
You're going to want to download this whole thing as it's been taken down in the past.
This has more than you'd ever want to know about every important component in your car.