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K&N cold air intake getting bad gas mileage.

  #1  
Old 10-04-2011, 08:51 PM
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Default K&N cold air intake getting bad gas mileage.

I just bought a 2002 Monte Carlo SS, and it came the intake installed already on there. I know it's the intake because I've owned previous 3800 motors and never have I experienced anything this bad. I've read that these thing s are suppose to increase your gas mileage. I'm not a speeder, so I know it's not my foot. Should I just go back to stock air box and filter?
 
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Old 10-04-2011, 09:38 PM
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i never got worse mileage with any of my CAIs...and if i did it was cus my foot was closer to the floor all the time
 
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Old 10-04-2011, 11:15 PM
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FYI - The K&N intake is not a true CAI. The box is uninsulated metal and transfers heat from the engine quickly into the intake space, also lack of lid and the oversized hole for the snorkel to come in doesn't help. You may want to try and insulate it to make it more of a CAI.

One thing you may want to explore is basic maintenance. A tune-up. A 2002 probably has significant miles under it. I'd consider:
- Air and Fuel Filters (since you have a K&N HAI, make sure the filter is clean)
- Plugs (AC Delco preferred, no Bosch plugs) and wires
- Check for signs of vacuum leaks and possible history codes in the computer
 
  #4  
Old 10-05-2011, 03:09 AM
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The car has 57,000 miles on it. Should I have a shop inspect for vacuum leaks? I doubt it needs a tune up. The car runs flawless, except for the horrible gas mileage.
 
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Old 10-05-2011, 06:40 AM
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How poor is the fuel mileage? Less than 20 mpg?
 
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Old 10-05-2011, 07:50 AM
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Yes, I would say about 16.
 
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Old 10-05-2011, 08:24 AM
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Originally Posted by YeahBuddy View Post
The car runs flawless, except for the horrible gas mileage.
There are a few things that affect gas mileage.

Catalytic Converters, plus they are known for going bad.
Front o2 sensor, this sensor tells the car the amount of fuel to dump.
Actual fuel injectors, they could get stuck open.
MAF sensor, gives the air readings to help the PCM figure out air/fuel ratio.

K&N could be pulling a lot more air, and the cars reaction to that is to just dump fuel at it. They also come oiled, and that oil can ruin MAF sensors.

You can TRY getting a MAF cleaner and spraying it. But really, I think the car's PCM is just dumping fuel because of the increase of air.
 
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Old 10-05-2011, 10:07 AM
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Originally Posted by ChibiBlackSheep View Post
There are a few things that affect gas mileage.

Catalytic Converters, plus they are known for going bad.
Front o2 sensor, this sensor tells the car the amount of fuel to dump.
Actual fuel injectors, they could get stuck open.
MAF sensor, gives the air readings to help the PCM figure out air/fuel ratio.

K&N could be pulling a lot more air, and the cars reaction to that is to just dump fuel at it. They also come oiled, and that oil can ruin MAF sensors.

You can TRY getting a MAF cleaner and spraying it. But really, I think the car's PCM is just dumping fuel because of the increase of air.
So how would I go about fixing the pcm?
 
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Old 10-05-2011, 10:15 AM
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Originally Posted by YeahBuddy View Post
So how would I go about fixing the pcm?
It's not so much fixing the PCM, as the PCM needs to be tuned for the increase in the incoming air.

You can attempt getting a "canned" tune from getoverkilled.ca or zzperformance.com but even those might not be able to dial in to your specific car's needs.
 
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Old 10-05-2011, 05:56 PM
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the pcm really should adjust for the increased air from the K&N, could be sucking in warm air and affecting the mileage
 

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