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#1 (permalink) Old 12-09-2011, 07:28 PM
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Default Fuel burning too rich

I got a AEM CAI intake for my 09 tc and the check engine light came on a few months after I got it and it is saying the fuel is burning to rich. They told me that the intake is causing that. Will that cause any problems other than slightly worse MPG? I tried to find the answer for this but all I could find were burning fuel rich with superchargers. Thanks guys.
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#2 (permalink) Old 12-09-2011, 10:01 PM
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I hate They, for They never tell you how to fix it just what the fault code is. They should have told you that running rich can burn out your plugs fast. I blew a set of plugs in 500 miles after putting my turbo in and not getting it tuned immediately, it was running rich as well, very rich. Depending on how rich it could do the same or just decrease efficiency. I don't know at what point the CEL comes on for rich and lean but I would bet it's beyond a desirable condition. In any case it should not be ignored.

If they said it was the CAI, then money is that the CAI uses an oil bath filter and that has clogged up the mass airflow sensor (that first little box about 12 to 18 inches from the filter). The could also be that They is talking out their tailpipe and just put the blame on the first non OEM part they see.

But my money is that the CAI has clogged up the airflow sensor.

Check to see that the sensor is installed correctly and make sure that the plug is seated good (probably is since you ran it for a couple months with no problems). If it is then more than likely the sensor has gotten gummed up or just doesn't work. I don't remember if you can clean them (i think you can, carefully) but if it's seated right then try cleaning it. If that doesn't work then it probably has gone bad and needs replaced. Take it off and have it checked, they can be checked. They were running about $120 for 3rd party several years ago (lets just say I know that bit of information from learning the hard way). If it's not bad then it might be mechanic time.

From when I was putting on my turbo I found out that oil bath filters (K&N, AIRam, etc...) tend to cause problems with the airflow sensor if the filter has too much oil on it. This causes the computer to not read the correct airflow which then causes the wrong amount of fuel, your case it's too much. Hopefully this is where your problem is and turns out to be a quick and cheap fix.
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#3 (permalink) Old 12-09-2011, 11:39 PM
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You can't really fix it...it's what CAI's do. Even if you reset your ECU (which i hope you did when you installed). It'll still come out on the rich side.

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#4 (permalink) Old 12-10-2011, 08:28 PM
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A CAI does not cause the car to run rich unless something is wrong. A cold air intake causes the engine to pull colder, denser air (but a very, very very small effect overall), meaning that if anything, it would make the car run lean IF the ECU could not trim enough to keep the AFR in check. But that is not the case. The very slight difference in air density (again, a CAI is not doing that much, little to nothing on a tC) is easily made up for by the ECU adding more fuel to the mix. That is the whole reasoning behind how they work. Think about it this way, your car can run in temps way below zero, or over 100 degrees, the difference in air temp and density in those conditions is WAY larger than the difference in pulling air from the top of the fender level vs pulling it from a foot lower than that If a few degrees difference in IAT that a CAI provides caused the AFR to be off even slightly, then your car would not operate when the temp dropped to 20 below zero. And running that smooth metal tube vs the stock in take does not allow the engine to pull in gobs more air like they like to tell you it does, or the CAI would make more than a measly few HP at the crank. In other words, the ECU and fuel system is more than capable with keeping up with the change in airflow or density.

If the car is running rich, the MAF is the very likely culprit. An oiled filter on a CAI can cause issues if the filter is over-oiled. But, the real issue with oiled filters is on an SRI, where the filter is closer to the MAF. The MAF does not get clogged really, since it is just a small sensor sticking down into the intake. The surface of the sensor gets dirty, which is what causes the problems.

1) Did you reset the ECU after you installed it? That may or may not help.

2)Remove the MAF, and clean with MAF cleaner. DO NOT touch the sensor element with anything, simply spray it out well with the cleaner and let it air dry.

3) Are you sure you have the correct CAI for the year model? A CAI for a 2005 will not work on a 2007+ for example, because of the MAF mount. You should have noticed that things did not mount up correctly if that were the case though.

There are vacuum lines you could have left off when you installed, but if that were the case, the car should be running lean since it would be pulling un-metered air into the intake.

For reference, what code exactly is the ECU throwing? Are you sure it is a rich code? And who is "they" ?

Not to be anal, but your fuel is not burning rich, your air to fuel ratio is rich. Rich means too much fuel for the amount of air, lean means too much air and not enough fuel.

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Last edited by engifineer; 12-10-2011 at 08:32 PM.
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#5 (permalink) Old 12-11-2011, 01:26 AM
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^^ pretty much this. Dude knows what's up.

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#6 (permalink) Old 12-23-2011, 10:08 PM
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Hey guys sorry for the late response. For some reason I did not get an email that you guys responded. Wow engifineer that was a lot of info. Thanks for all of it.

I have an update for it but I am not sure if it is related. It has been driving fine and then one day the car started to sound like it was burping (not from the exhaust) and then the car just shut off completely as I was driving. The power steering wouldn't work anymore and the brakes barely did. I coasted into a parking lot and then waited 30 seconds and it started fine. I drove back to work and it drove fine as if nothing had happened. Do you guys know what could have happened? And do you think it is related to the rich air to fuel ratio? Someone at my work think something in the computer blew but I really have no idea.
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