Help Check engine light

[1996 318ti NY]

I installed a K+n filter on the intake yesterday took off the stock air box and such after running ti for a few minutes my check engine light came on =/ i reinatlled the stock airbox and everything and its still on what is happening here and how do i fix it?

[roadrash]

You need to get error code from the OBD system. Many auto parts places will read the code for free. Once you know what the code is, you need to fix that problem before the CEL will stay off. Some codes need to be cleared, some will go away after a number of "drive cycles."

[713bmw318ti]

the check engine light turns on in my car like once every 2 weeks.
Anyone in houston tx with a code reader that will check the CEL
for me. I will buy you a 6 pack of beer for your help.

[J!m]

I am on Long Island and can scan your codes as well as re-set any errors for you.

I have CarSoft running sucesfully.

I can also perform any needed repairs, but I do that on the wekends in CT.

PM me if interested...

[spidertri]

I know on VWs the MAF was very sensitive to the oil used on the K&N filters. If the filter was over oiled it would screw up the MAF and throw a CEL. Maybe you used a bit too much oil?

[BMW_318TI]

Have you tried reset the ECU?

[b.u.ti-ful]

Did you check the engine?

[michaelmyers]

Hi, I also have the same problem. The my check engine light came on after my intake install. Where do I connect the sensor that goes to the stock airbox? My car feels horrible right now! Thanks

[J!m]

That senmsor needs to be in the intake stream, before the air mass meter.

Without that charge air temp reading, the DME cannot accurately determine the volume of air being ingested, and therefore cannot properly meter the fuel.

So, it will run like crap.

[Philly]

if all you did was buy a cone filter or cheap kit, you will need to drill out a spot after the filter and before the MAF.
I ghetto rigged one up when I first bought the car. Was a waste of money. lol

[michaelmyers]

Yes i bought a ebay kit, ha! Great price, but now I face the problem of not having a hole to insert that sensor in! Sucks!

[HardxWood]

Yes u definitely need a hole for that sensor.. but if you're car happens to have a secondary air pump (the black cylindrical thing that would be beneath your MAF sensor) you'll notice that you now have no place to put the tube on that thing (it's connected to the post filter side of airbox stock). You'll need to get ahold of a breather cap or filter for that hose bc it was previously sucking filtered air from the box and continues to crave filtered air. Don't get some stupid breather cap tho.. i'd recommend an actual cotton filter that can be "plugged" into the hose. that hose is only like 1"-1.5" in diameter so its not big. once you've got that done either get someone to clear the fault codes or if u have an aftermarket stereo that wont lock on you, just disconnect the battery.. that oughta clear that check engine light. if this doesnt apply to your car bc u don't have a secondary air pump, sorry i could help, but i'm sure there are others with cars like mine that have that weird emmisions stuff like that in it... oh well.. that california's emissions laws for you.

[Dusty_Hale]

For the MIL light being described by the original poster, your computer was running under the assumption that the stock components were in place. When you opened up the air intake box and let it run, it sensed more air coming in, which caused a lean condition. In an attempt to compensate for this, the computer told the injectors to dump more fuel to get the air-fuel mixture back to stoich. While doing this, the computer also advanced timing to compensate for the extra fuel that was now being delivered to each cylinder. After the initial calculations were set, the computer noticed that the signal from the MAF did not match the volume of air that was actually going into the engine. As a result, more fuel was dumped, and ignition timing was set at its most advanced allowable setting, most likely in between 6 and 8 degrees advanced. Then, you put the air cleaner assembly back together, and the computer noticed an instant rich condition. The computer told the injectors to deliver less fuel in an attempt to compensate for the rich condition, that would have eventually caused a rich misfire, and fouled the spark plugs if left unchecked. Now the timing has to be retarded, otherwise an event called "Detonation" would take place. This is also known as "pinging." So, the computer is now trying to get the air-fuel mixture back to stoich (14.7:1 AFR). Also, another possibility for the MIL light is that while the computer was running rich, raw fuel may have escaped the cylinder and may have gotten into the exhaust stream. In that case, it burns off in the catalytic converter, however, if you had fuel additives like octane boosters and the like, you may have contaminated your O2 sensor. In which case, your MIL light is for an O2 sensor malfunction. This is unlikely based off of the time-line that you described, but it is not impossible.

Basically, your computer should clear itself after a few drive cycles. It is trying to re-learn it's basic strategy. Once it has everything worked out, you should be good to go. If it doesn't go away, then the computer is trying to compensate for something that is not setting itself the way that it should.

I give this example because of the conditions that you described in your initial post. Is there anything else that you have tinkered with that may have caused something to become unplugged?