G35 rough start

[bowlofturtle]

My 2005 G35x lately has been having a hard time starting from a cold start. (30-50 degrees)

Car has 130k now, no CEL at all. Plugs were done at 100k. All normal maintenance has been done. No changes or new parts the whole winter. Issue only happens once in the morning or late night when i leave work.


I found a video of exactly what is happening with my car. The car starts everytime but just the first few seconds its a little iffy. The comments in this video says the owner fixed it with cleaning his MAF sensor.

I'm going to clean out the TB shortly and take another look at the plugs. I might get a can of MAF cleaner because it cant hurt but i'm doubtful on that.


Anyone have thoughts? Its doesn't happen all the time. NO CEL to point me to anything. No vac lines noticeable broken.

 

[mclasser]

Cleaning the TB & MAF is a good start. Just be careful not to push the butterfly valve with your fingers. These Nissan electronic TBs are sensitive [censored].

 

[Hall]

Originally Posted By: bowlofturtle
I might get a can of MAF cleaner because it cant hurt but i'm doubtful on that.

CRC sells (at least at Walmart) a package with a can of MAF sensor cleaner and TB cleaner. They're smaller cans but at least with the MAF cleaner, it will last a long time. That's what I'd start with and focus more on the TB too. There are various 'guides' out there and LOTS of conflicting information -- disconnect the battery, do NOT disconnect the battery, disconnect the TB harness, don't disconnect, don't touch the butterfly, it's okay to touch/move it, etc, etc.

I recently cleaned mine because of an idle fluctuation but mine wasn't acting like the one in the video. That's really odd the way it was bouncing the RPMs at first ! What mine was doing was occasionally when I would stop at a light, stop sign, etc, the idle would drop to ~500 and then back up to normal. Never stalled or anything but it just didn't seem right. Cleaning the TB -- which I could still clean more thoroughly -- seemed to take care of it. FWIW, I didn't disconnect the battery nor the TB connections and I also opened the butterfly (but only slightly). I performed the various 'throttle position leaning...' steps a few days later though they didn't seem necessary (can't hurt to do them anyway).

 

[Trav]

How long has it been doing this? MAF issues generally trip a CEL, but moisture in the fuel system wont. Did this happen after filling the tank some time ago? Just thinking outside the obvious, clean MAF, TC, hoses, plugs, etc.

 

[bbhero]

One thought I have here is if this motor is like my 3.5 VQ... My car is sensitive to gasoline quality. If I get questionable gas my car will have a few misfires in each cylinder. Most I said was 6 in cylinder number 1. But all of them had at least 2. If I get good quality gas... Zero misfires. The Shell station near me I have zero issues. A Shell station at Ashland I actually had a few misfires in each cylinder. 2 to 4 in each cylinder. And the car had a bit of a noticeable stumble at idle.

So, I'd your motor is like mine. Gasoline quality does matter. To a good degree more than one would think.

I hope that your situation is rectified very, very soon.

 

[Hall]

The motors are (generally) the same. It's a VQ35?? in an '05. I don't have one nor try and keep up but I suspect it's a "VQ35DE". I have an '08 G35X and I think starting in '07, the engine type became VQ35HR.

The OP seems to describe this as happening commonly now, after cold weather. I'd guess he/she would have gotten multiple fuel fill-ups over time.

 

[bbhero]

Off course I left off the de part... Not a big deal. The HR version will do better with certain types of oils ( a bit of esters help them) . It has the DLC on the cylinder walls.

Still the VQ 3.5 in my car runs noticeably rough on certain gas. I got either bad gas or totally wrong octane gas from a Exxon gas station in town. Car ran very rough on it. If someone is getting roopty Doo terrible gas then it will not help that motor run well or start well. That I can say unequivocally. My car has 226k miles on it. I got it with only 39k miles.

Not saying this is the problem in this circumstance. But it could well be a part of it. Maybe a bigger part than one would first think or realize. And it may well not be a part of it at all. I'm just saying it because I have noticed how sensitive my car is to gasoline not being up to par.

 

[bowlofturtle]

Originally Posted By: Trav
How long has it been doing this? MAF issues generally trip a CEL, but moisture in the fuel system wont. Did this happen after filling the tank some time ago? Just thinking outside the obvious, clean MAF, TC, hoses, plugs, etc.


Its been at least 3 fill up, since the car gets 18mpg, LOL. Time frame of about a month. I think it was actually doing better in the freezing cold then this 40-50ish degrees. But all at the same Costco gas station. I log and track all my MPG and it has not dropped or increased.

This is a VQ35DE motor for the ones in question. Its been solid minus a few sensors here and there.

 

[bbhero]

Do you have a OBD II scanner?? Seeing live data and misfires on there could be a little helpful. I did not have a code for the misifires I had in my car. Evidently not enough to cause one. But sure enough there were some. And it validated my experience with how the car felt at idle. Rough= some misfires. Smooth and normal= Zero misfires. Questionable gas or bad gas= misfires. Known
good gas that runs normal and smooth as silk= Zero misfires.

 

[Trav]

It makes sense that it runs good when very cold as the mixture is much richer. This engine has an IAC valve under the intake plenum that may cause symptoms like the one you have when its carboned up without throwing a code.
You need to use a scan tool and look at the intake air temp, coolant temp, misfire count, etc.

 

[cronk]

The 3.5 in my wifes 11 Quest was starting rough and a throttle body cleaning solved it.
It appears it was carboned up to the point of becoming slightly sticky. I suspect the electronic throttle was not opening enough for the cold start high idle.