My 09 Maxima has been engine knocking at speeds between 0-20mph especially when running air conditioner and the idle is high now which in turn caused service engine soon light to come on.

 

Sounds like you have a problem.

 

Car still runs relatively good it idles higher than what it should and the engine knock normally only happens at 0-20 mph and when it's hot outside while running air conditioner

 

Well that's certainly better than not running at all I suppose.

 

I agree, should be all set to go. It's running, didn't scan for codes, I'd say smooth sailing.

 

I did scan for codes and the code it threw was P0171 which points to the MAS air flow sensor, but it was replaced less than six months ago.
The dealership said I had a crack in my air intake manifold which is a hard plastic. It was replaced just a week ago and today it did exactly what it then. High idle service engine soon light came on.

 

That MAF sensor could be bad especially if it was replaced with a cheap aftermarket, always go OEM with those electrical components imo.

 

The MAS was a after market which has a life time warranty supposedly. I'll be taking my car back in Monday and hopefully they'll get it right.
My Maxima has 153242 miles on it that I bought with 146000 on it and since then I've sunk over 3 grand in it fixing different things. I think it's time to move on from Nissan

 

LtLeary has a 7th gen with just about half a million miles on it. It's not a "Nissan" thing, you bought a bucket. Even with planned obsolescence, any car can be maintained to last forever, or not be maintained and destroyed young.

Taking a car anywhere can drum up $3k in repairs quick. Most of us around here do our own work, that's why we are here. It's Tuesday, how did yesterday's appointment go?

 

I got my car back and I must say it's running like a charm not to mention a smooth idle.
The dealership performed what is called a ECM reprogram and a air idle relearn because my air intake manifold was cracked which had my air/fuel ratio volumes off. Once this was done no more code or SES light.

 

Awesome!