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Jay
Jay, Certified Infiniti Technician
Category: Infiniti
Satisfied Customers: 18714
Experience:  20+years, Nissan and Infiniti experience and currently now working for a Infiniti Dealer
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Infiniti G37 Sport: I have an 08 infiniti g37 coupe. It has

Customer Question

I have an 08 infiniti g37 coupe. It has a hard time starting. I can turn it on and it will idle really rough and then turn off. If i unplug the MAFS it will turn on. Idle really high. Then i plug them back in and then turn the car off and then turn it back on with the MAFS connected and it starts normal. What do you think my problem is being caused by? I have 55k miles
Submitted: 1 year ago.
Category: Infiniti
Expert:  Jay replied 1 year ago.
Hi, My name is***** happy to help you. During our conversation, I may be presenting you with different things to try, and ask you some Questions to get a better understand of the issue so I can answer your question properly. So stick with me to the end, and I am sure we should be able to get this issue resolved for you!
Thank you for that description. You mentioned you brought a 1 MAF sensor, where did you buy it?
Customer: replied 1 year ago.

I bought it at a parts store. Autozone. It is a hitachi brand

Expert:  Jay replied 1 year ago.
Ok, First thing, When it comes to After Market Electrical parts, they never work right and can leaving you scratching your head and replacing more parts than you need. After Market MAF sensors if you get one that works, will flat line 02 sensor operation which will have you chasing your problem a totally different direction which costs you more money.
If you still have the original MAF sensor, try using MAF sensor cleaner on both of them and see if that helps.
Now, if you have cold air intakes or K&N air Filters, that could cause some of the issues you are describing as well.
Do you have those mods on the car?
Customer: replied 1 year ago.

I have tried cleaning the old ones but i get same results. The car throws 2 codes. System too lean and random cylinder misfire. Could the maf have to do with that too? I am running everything stock

Expert:  Jay replied 1 year ago.
How many miles on the car?
Customer: replied 1 year ago.

55k

Expert:  Jay replied 1 year ago.
What are the exact codes your getting please?
Customer: replied 1 year ago.

P0171 and p0300

Expert:  Jay replied 1 year ago.
The fuel system lean code is normally due to a MAF sensors not metering air properly. When you get that imbalance of air and fuel trim, it can cause running issues. So it could cause the Misfire code are well.
Do you have a full blown scanner that can monitor fuel trim readings? or is it a code reader?
Customer: replied 1 year ago.

Its just a code reader. How can i test my MAFS after i re-clean them to see if they work

Expert:  Jay replied 1 year ago.
When you have MAF sensors not metering air properly, the only real way to determine this is with a full blown scanner monitoring fuel trim readings.
You want to make sure you have OEM sensors, not ones from a auto parts store. You also want to use CRC MAF sensor cleaner to clean the MAF sensors and see if that helps. If not, it may require one of both MAF sensors to be replaced.
If you have any more questions on this, please feel free to ask.
If not, and you're satisfied with my help, please Rate me. I hope I have provided you with Excellent Service.
Thanks Jay!
Customer: replied 1 year ago.

Also during idle. When i step on the gas the car seems to kind of bog down. Instead of rpms going up they go down then go up. For instance car idles at 700 if i accelerate rpms drop to 500 then slowly move up until 3500 then shoot up really fast. And while in 1st gear. If i press the gas pedal al the way it feels like theres no power. It slowly accelerates. My g35 is faster and it shouldnt be that way from my POV.

Expert:  Jay replied 1 year ago.
That description sounds like a MAF sensor issue.
Do you have a scanner to monitor fuel trim readings?
Customer: replied 1 year ago.

Ok. So i returned the maf from the auto parts store and got 2 new ones from infiniti. The car does the same thing. Wont turn on unless i disconnect them. Once the car is warm i reconnect them and it will start just fine. Also i have the same issue when i rev it in neutral. Revs fine if i dont push pedal to the floor all the way. But when i floor it, it does ok till 3k rpm then bogs down then after 4k it does fine. While in 1st gear i floor it and it will accelerate really slow as if i was just bearly touching the gas pedal. Same codes keep coming up. P0171 and p0300

Customer: replied 1 year ago.

Ok. So i returned the maf from the auto parts store and got 2 new ones from infiniti. The car does the same thing. Wont turn on unless i disconnect them. Once the car is warm i reconnect them and it will start just fine. Also i have the same issue when i rev it in neutral. Revs fine if i dont push pedal to the floor all the way. But when i floor it, it does ok till 3k rpm then bogs down then after 4k it does fine. While in 1st gear i floor it and it will accelerate really slow as if i was just bearly touching the gas pedal. Same codes keep coming up. P0171 and p0300

Expert:  Jay replied 1 year ago.
Ok... There has to be a vacuum leak on the car causing your issue. Was any work done on the car recently?
Customer: replied 1 year ago.

the only work that was recently done were the spark plugs. But i dont hear any vacuum leaks. I will do the smoke test and see how it does. What does the ecm reflash from infiniti do?

Expert:  Jay replied 1 year ago.
Let me know what you find with the smoke test.
Customer: replied 1 year ago.

I did the smoke test. Nothing leaked. Checked everywhere. Can i email you a video of how the car runs to see if you can figure it out?

Expert:  Jay replied 1 year ago.
Can you put the video in a Dropbox or something to share it or upload it to you tube and share the link?
Customer: replied 1 year ago.

On the video i floor the gas pedal in neutral and this is what happens.

https://youtu.be/mOFv8mh0moE

Expert:  Jay replied 1 year ago.
video marked private
Customer: replied 1 year ago.

Try it again. Sorry

Expert:  Jay replied 1 year ago.

Kind of a Quick video.. It almost sounds like the exhaust is restricted.. Do you have any type of Mods to the car what so ever? Cold Air Intake? K&N air Filters? Exhaust?

Something came to mind, and I hope that isn't it. But let me know about the Mods

Customer: replied 1 year ago.

I had intakes at 1 point but it didnt do anything like that. I sold them and put stock back on. It doesnt have aftermarket exhaust or anything. What do you think is going on?

Customer: replied 1 year ago.

do you think it would help if i disconnect mufflers. Take the pipe off after the headers?

Expert:  Jay replied 1 year ago.
Can we continue later this evening? I am normally online around 6 or 7 pm EST and online till 10 or 11 pm at night.
Let me know.. Then I will tell you my thoughts and what you need to do.
Customer: replied 1 year ago.

Yea

Customer: replied 1 year ago.

also. With the car not turning on unless i disconnect the mafs, once it turns on once and i plug them back in and let it warm up for a few minutes. I can turn it of and turn it back on with the mafs connected. Its just everytime that its cold i have to unplug them.

Expert:  Jay replied 1 year ago.
Ok.. I am here.. How handy are you. I am thinking you may have a broken valve spring causing your issue. That is why it sounded like a vacuum leak and is why it runs ruff. With 55k miles, I can't see the exhaust being a problem. But you need to do a cylinder leak down and compression test on all the cylinders to check and see which cylinder has the issue so you can isolate the problem. Once you know the cylinder, you can remove the valve cover and apply press to the spring and see if it seems loose. But that is something I have seen quite a few times. I would say 5 times in the last 5 years.
If you have any more questions on this, please feel free to ask.
If not, and you're satisfied with my help, please Rate me. I hope I have provided you with Excellent Service.
Thanks Jay!
Customer: replied 1 year ago.

I did the compression test. Cylinder 1,2,3,4 i got a reading of 240. Cylinder 5,6, i got a reading of 260. Is that good or bad?

Expert:  Jay replied 1 year ago.

That is good compression. The minim is 178.

What about leak down?

Customer: replied 1 year ago.

I will get back to you with those results tommorow.

Expert:  Jay replied 1 year ago.
ok.. Talk to you tomorrow.
Thanks Jay!
Customer: replied 1 year ago.

1 - 3.1%
2 - 3.2%
3 - 3.1%
4 - 3.5%
5 - 3.6%
6 - 3.5%

leak down test results

Customer: replied 1 year ago.

Cold start video. Wont stay on unless i disconnect maf sensors

https://youtu.be/Mr2oPzrGAfk

Expert:  Jay replied 1 year ago.
is this car a stick?
Customer: replied 1 year ago.

Yes

Expert:  Jay replied 1 year ago.
ahh.. did you have a clutch done?
Customer: replied 1 year ago.

Not that i know of. The car was like that when i got it

Expert:  Jay replied 1 year ago.
I am wondering if the flywheel is off 1 tooth which is causing your issue.
The only way to determine this is to remove the transmission and clutch to inspect the fly wheel
Is this something you can do? Do you have a scanner that can monitor intake timing at idle?
Customer: replied 1 year ago.

But if the flywheel was off. Wouldnt i have that same problem everytime i try turning it on? This only happens at cold starts. Once it warms up it will start without any problems And with the mafs connected. Dont have a scanner that does all that but i can check to see if i can find one and rent it

Expert:  Jay replied 1 year ago.
Well, we need a scanner. Monitoring Fuel Trim readings as well as intake timing readings will really tell you what is going on.
Unplugging the MAF sensors is making it run default readings which could be compensating for what ever the issue is.
If you can rent one, I am sure we can isolate your issue. But if you rent one it maybe better if we talk about your issue on the phone using additional service.
Let me know if you can rent one.
Thanks Jay!
Customer: replied 1 year ago.
Forgot to show you a video of wheN i first start the car with no mafs connectedhttps://youtu.be/tGeWR6N7TW4
Expert:  Jay replied 1 year ago.
That almost looked like bad throttle chambers when the idle surges like that.
Customer: replied 1 year ago.
i havent had any luck finding a full blown scanner. But as far as throttles. Ive cleaned them. They make a noise kinda like the ballast do when they turn on. They make they noise when the car is with the switch on but the car off
Expert:  Jay replied 1 year ago.
What did you use to clean the throttle chambers?
Customer: replied 1 year ago.
Crc throttle body cleaner. I took them out. They werent that dirty but went ahead and cleaned them anyway.
Expert:  Jay replied 1 year ago.
That maybe part of the problem. You can't use straight up throttle chamber cleaner on these throttle chambers since they are electronic. I use CRC MAF sensor cleaner cause they are electronic. Regular throttle chamber cleaner can damage the throttle chambers.
Plus any time you replace or clean the throttle chambers you have to do a idle Relearn.
So you may need to replace the throttle chambers at this point and do a idle relearn.
Thanks Jay!
Customer: replied 1 year ago.
But it did that before i cleaned them. After i cleaned them same thing happened. There was no change. After a few minutes Idle stops surging like that and goes to 1k and stays there
Expert:  Jay replied 1 year ago.
Does it run with MAF sensors plugged in so a idle relearn can be done?