Rough idle at “cold start” only in warm ambient temps??

A forum for lovers of Infiniti's hot-rod crossover, the FX! In 2014, all FX models will be named Infiniti QX70, in line with Infiniti's new naming structure.
Infinitiball
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Joined: Tue Jan 09, 2018 12:36 pm
Car: Fx35

Rough idle at “cold start” only in warm ambient temps??

Postby Infinitiball » Tue Jan 09, 2018 12:44 pm

I have a 2011 Infiniti FX 35 that has a rough idle immediately upon cold start until the computer gets the engine to high idle where it smooths out and runs normal from there. The issue only occurs on the first start of the day and only occurs when the weather is warm outside (60F+). When it is cold outside the coldstart is flawless. The dealership performed an idle relearn in the summer which made the problem go away for a couple weeks but it then slowly came back while it was still warm but has since disappeared in the winter.

I have had our dealership look into this issue several times over the last year with no success. They even kept the vehicle for a full week and claimed to not be able to replicate the problem and could not find any codes anywhere.

Any ideas as I am out of options with the dealership?


EdBwoy
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Re: Rough idle at “cold start” only in warm ambient temps??

Postby EdBwoy » Tue Jan 09, 2018 11:33 pm

Do you know the health of the PCV valves?
Also, any idea if you throttle body(s) have been cleaned recently?
I would try that and cleaning the MAF (mass airflow) sensor to see if anything changes.

I have had a problem in the past that was the opposite of yours. Starts well when cold, and would stumble and die when warm. The idle relearn cured that for me.

Infinitiball
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Joined: Tue Jan 09, 2018 12:36 pm
Car: Fx35

Re: Rough idle at “cold start” only in warm ambient temps??

Postby Infinitiball » Sun Jan 14, 2018 8:01 am

EdBwoy wrote:
Tue Jan 09, 2018 11:33 pm
Do you know the health of the PCV valves?
Also, any idea if you throttle body(s) have been cleaned recently?
I would try that and cleaning the MAF (mass airflow) sensor to see if anything changes.

I have had a problem in the past that was the opposite of yours. Starts well when cold, and would stumble and die when warm. The idle relearn cured that for me.
I have no idea. The vehicle has around 65k miles on it and I have never serviced the MAF or PCV. Would it make sense that they would operate differently in different temps? Is the an intake air temp sensor somewhere?

Thx

EdBwoy
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Re: Rough idle at “cold start” only in warm ambient temps??

Postby EdBwoy » Sun Jan 14, 2018 2:05 pm

No intake temp sensor that I can think of, off the top of my head.
You said when it was cold outside, there were no issues... I should have asked for clarification whether it was good for the 2nd, 3rd, 4th start etc. I know that the 1st start of an engine (regardless of ambient temp) = a cold engine.
Also, the fact that an idle air relearn made it good for a while, makes me think that at minimum the car would need the throttle body cleaning... followed by an idle air relearn again.

04pathse
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2008.5 Mazda Mazdaspeed 3

Re: Rough idle at “cold start” only in warm ambient temps??

Postby 04pathse » Sun Jan 14, 2018 2:46 pm

Many cars have the "intake air sensor" on or inside the MAFS, if not it would be a separate sensor near or on the intake air duct.

amc49
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'17 Altima

Re: Rough idle at “cold start” only in warm ambient temps??

Postby amc49 » Sat Feb 03, 2018 5:42 am

X2 to that, the MAF almost works like a temp sensor.

Could be a leaky injector that leaks to be too rich at a warmer start and why dead cold would run fine. Or possible vacuum leak that has less fuel allotted to cover it in the warm engine fuel map than a cold start does since they need to be rich.

Need to get car where it will do it and then using a scanner read a live data output off the first O2 to see if hanging rich or lean, that maybe will tilt things one way or the other.

The TB aircrack and PCV orifice need to be clean.


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