Hello

After doing a lot of research my wife and I finally decided we wanted to purchase a EX35. Iv'e heard/read a lot of good things about the car and the motor from what Iv'e read is also pretty reliable. Iv'e owned many Hondas so this is my first Nissan/Infiniti.

So we test drove the EX35 on two separate occasions and the car ran and drove great. We ended up buying it, and now less then a week later I'm already having an issue with it. To start I have to say the issue started pretty shortly after getting gas from a gas station that I normally use with all my other cars. The issue is mostly happening when the car is cold and not fully warmed up. Once the high revving after first starting, it will drop down and idle some what rough. Also when you are driving it shortly after starting it will loose power at lower rpms and studder. Also after first starting it up you can have the car in park and slowly give it gas and every time right at 2000rpm it will bog down, studder and then once giving it more gas it will go over 2000rpm. There are no codes showing either

So far I have taken the MAF sensors out and cleaned them, but that didn't seem to solve the issue. The sensors looked pretty clean, but I noticed that the owner before me installed K&N filters which most of the time have an oil on them, so there was some oil in the air box, but the tubes where the sensors where dry.

I was going to possibly try replacing the sensors and spark plugs at this point to see if that does anything.

Any help or suggestions would be awesome, Thanks!

sounds like this:

idle-issue-stutter-solved-t616320.html

After owning 3 Infinitis for over 12 years I would suggest the following. Invest the $99 to a reliable Infiniti dealership for a diagnostic review of your problem. You have nothing to lose and a good dealership knows more than you and me. If they find anything and recommend repairs.. they will back up and guarantee their work. Otherwise you may be throwing good money at bad and buying parts not needed. Good luck and let us know how you make out.

I was hoping that changing the plugs and cleaning the throttle bodies was going to fix the issue, but it didn't. I'm sure this car was on the original plugs and the the throttle bodies were pretty dirty so these were things that needed to be done anyway.

The hesitation at or around 2000rpm seems to be a pretty common thing with these motors. Iv'e been seeing a lot of people posting the same thing on 350Z forums as well about this. However the things that people replaced to fix the issue seems all over the place.

Basically at this point my car stutters and runs pretty rough when starting it in the morning. After warming up it doesn't really seem to do it anymore. Also the car hesitates right at 2000rpm every single time you slowly raise the rpms up. This also really only seems to be worse when cold and gets better as the car warms up, but from what I can tell is some what always there or is very subtle when its warmed up

I have never had that 2000 rpm hesitation. The worst thing I have experienced relating to the motor would be stalling / not starting right away after it was hot and stopped for a short time (getting a coffee, for example).. this was fixed when I cleaned the TBs, MAF sensor and changed the plugs.

I would have the dealer diagnose also... $99 for peace of mind and to point you in the right direction is worth it to me.

Lostex35: I have solved/nearly solved stalling issue. I sometimes could cause the stall by accelerating slowly to 1200rpm and quickly release accelerator pedal and the rpms would drop to 400rpm or die. I was getting the P0001 code.
I cleaned the tbs off the car & cleaned the mafs but was not careful reconnecting the tb hoses. There is a flared section on the pipes at the bottom of the tbs and I did not have hose above the flare. Once I double checked the connections the issue happened once but has been running perfectly for the last 5 days.
After cleaning the tbs off the car I had to relearn pedal position,tb closed & idle air volume settings. Since the re connections I am unable to make the car fail. The oily K&Ns should suggest a thorough cleaning of tbs & air intake tubes and the plastic housing beyond the tbs. You must allow the K&Ns to thoroughly dry before reinstalling.
Good Luck.

Yea I tried all of that and it did nothing for my issue. Mine isn't ever stalling, its just running rough and jerking back and forth at lower rpms the first 15ish mins of driving it in the morning. Basically as soon as the car is warmed up its runs and drives great

Have you tried the idle air volume (re)learning procedure?

From the Field Service Manual:

"3.PERFORM IDLE AIR VOLUME LEARNING
Without CONSULT-III
NOTE:
• It is better to count the time accurately with a clock.
• It is impossible to switch the diagnostic mode when an accelerator pedal position sensor circuit has
a malfunction.
1. Perform Accelerator Pedal Released Position Learning. Refer to EC-17, "ACCELERATOR PEDAL
RELEASED POSITION LEARNING : Special Repair Requirement".
2. Perform Throttle Valve Closed Position Learning. EC-17, "THROTTLE VALVE CLOSED POSITION
LEARNING : Special Repair Requirement".
3. Start engine and warm it up to normal operating temperature.
4. Turn ignition switch OFF and wait at least 10 seconds.
5. Confirm that accelerator pedal is fully released, turn ignition switch ON and wait 3 seconds.
6. Repeat the following procedure quickly five times within 5 seconds.
- Fully depress the accelerator pedal.
- Fully release the accelerator pedal.
7. Wait 7 seconds, fully depress the accelerator pedal and keep it for approx. 20 seconds until the MIL stops
blinking and turned ON.
8. Fully release the accelerator pedal within 3 seconds after the MIL turned ON.
9. Start engine and let it idle."

Short of that, I'd also bring it to Infiniti or Nissan and let them put it on the Consult-II and diagnose it. May be a bad PCV valve, throttle valve problem, wrong idle speed, etc.

No codes & issues only when cold. I bet the lot where you bought the car had it fully warmed up when you did test drive!!

Anyway, it seems your issues are air/fuel issues at low rpm and due to to drive-by-wire technology this can be difficult to run down. The suggestion by sherwooa above is a good start and if you are confident in your cleaning of throttle body and if issue prevails I would then go to a dependable shop you know for a full diagnostic scan.

good luck

My next thing I'm going to replace which most likely could use replacing anyway is both upstream o2 sensors and the coolant temp sensor. If any of these don't fix the issue I will most likely bring it to someone who can run a diagnostic scan on it.

I haven't tried any of the relearn procedures yet only because once the car is warmed up it drives fine without any hesitation. So this would lead me to believe that someone is not working correctly making the air/fuel ratio right when its cold. I would think for the learning procedures to work the car would have to be running/driving bad all the time

I wouldn't go replacing O2 sensors and coolant temp sensor unless you have good reason to believe they're out of spec. Rough idle when cold doesn't suggest either of those to me. Are you experiencing poor gas mileage too? If not, I wouldn't suspect O2 sensors. How many miles are on the car?

Personally, I'd bring it to someone who has a Consult-III to diagnose before I start throwing more parts at it.

To add, I'm pretty sure the EX ignores the O2 sensors during cold start anyway, so those won't really help your problem.

I'd sooner suspect carbon buildup (valvetrain), vacuum leak, possibly bad injector(s), coilpack(s), and/or fuel pump.

What octane of gas do you use?

Iv'e only had to put gas in it once since we recently bought it and I put 91 in it. Its very odd cause the it really only stutters when driving it right when it most likely reaches its operating temp, and then shortly goes away and drives completely smooth and fine. Is it possibly for it to be to be a injector issue and for it to only happen for a short time and then go away?

I'm going to just start with replacing the sensors which I got pretty cheap anyway and go from there. It can't hurt to replace these anyway with the miles it has on it.

Did you check your PCV valve?

Yea I just replaced the PCV and the Coolant sensor and it's still doing it. Well I'll see if the upstream sensors do anything and if not then I'm giving up and at least having a place run a test on it

Well I replaced the upstream o2 sensors and MAF sensors and that didn't fix the issue. In a way I'm glad I just replaced the o2's now so I dont have worry about for a while now, and maybe it will help with mpg a little bit. At this point I'll have to just bring it some where to get a diagnosis or get some software to get betters readings and try and figure it out myself. I'm always worked on all my own cars and have never had to bring anything into a mechanic or dealership so I don't really want to start now. I wish this thing would just throw a code which would make things so much easier

So sorry to be repetitive. But when problems like these exist....it's usually best cost wise and time wise to find a reliable dealership that has the software to diagnose your problem without throwing money to parts and guessing. I've owned a car dealership for 25 years ....in my youth and know these days it doesn't work to guess. Technology!!! Spend the $99 or close to a reliable dealership which will guarantee their diagnosis and end it!!! Good luck my friend. Let us know how you make out.

Yea Im just going to be bringing into a mechanic to run some tests on it. Iv'e also been reading that the Oil Gallery Gaskets on these motors are also know to blow out because they are made out of paper, which causes low oil pressure and will not display any error codes. Apparently Nissan never admitted this was their fault, but now the updated gaskets are metal and not paper. Also seems like replacing them is a pretty labor intensive job.

Never heard anything about blown out gaskets causing low oil pressure..etc. Where in the heck are you hearing that? Just take your car to the dealer and have them check it out. No more talking about it...just do it.

just type in QV35R oil galley gasket and there are tons of info on these failing. Its mainly in the 350z and G35 but they all have the same motor and gasket so this can easily be an issue that an EX would have as well. Nissan used paper gaskets which were breaking/blowing apart and causing an internal oil leak and would also result in low oil pressure. The new gaskets are magically changed to metal even though they said there was never an issue with the paper ones. There also a lot of pictures of the gaskets blown out online

Not saying this is what my issue is, just stating this is a known issue with these motors

Its been awhile but I have new info: I had a leaking radiator while diagnosing the stall issue and I have come to find out that the ECT sensor (engine coolant temp) has an influence on the air/fuel output from the ECU due to erroneous readings (out of range) of coolant levels & temps.
Just replaced the radiator with a Murray product recommended by my local indy shop ($635 out the door to and since they could not get it to stall.
Hope this is helpful to y'all!!!