My CEL has been coming on and off for couple of months. it is kind of bothering. I took my car to dealer's service for inspection last Friday. After 3 hours waiting, I was told by service manager that there is nothing wrong with my car. Mechanics carefully went through exhaust inspection, but nothing wrong with O2 sensors. Computer scan indicated both banks are runing lean. They concluded that my HKS intake might suck too much air into the engine, which is out of manufacturer's spec and causes the CEL on. This conclusion sounds resonable, but I am still wondering if any other people had the same problem. I have used Injen CIA, K&N filter, and weapon intake before, they were all competable with stock ECU. This is the first time I got this kind of problem. Will ECU reflash solve the problem?

 

Honestly, im not sure on a solution to your problem.


But from what I believe, theres no such thing as getting "too much air into the engine". Its what It lives for [complimentary with gas]. Correct me if im wrong.

 

even if the intake sucked in more... i would believe the ECU would compinsate for the air flow... so the ECU would increase injector "on time"??

 

I would believe the air/fule ratio is out of factory limit then the 02 senors recieve the information and turn CEL on. It could be possible, but I am imagining. Dealer's explaination is the only reliable source so far. If anyone knows what is going on, please help me out.

 

What other breather/exhaust mods do you have? What year is your car? What tranny? It is entirely possible that the ecu is simply unable to keep up with the amount of air getting into the engine. If this is indeed the case, it's not necessarily the fault of your intake, rather the combination of all your breather mods together.

There's always the possibility that you're not getting enough fuel because of clogged injectors, a dirty fuel filter, or even a fuel pump that's not quite right. Have you noticed any pinging?

 

I have an 04 G35 coupe 6MT with pro1 headers, Crawford cats, and NISMO exhaust. These parts have been on my car for 8 months,never turned CEL on or got problem. In Feb, I used HKS mega flow air filter to replace my weapon filter. After 2 days, the CEL was turned on on my way home and on and off since then. the HKS filter is bigger than standard filter size, which is 200X90.

 

Adding a bigger air filter should not make you suddenly run lean enough to trigger the ECU to throw a lean code. The ECU will compensate using the MAF reading. However, if you have a leak/bad seal on your intake AFTER the MAF, guess what? You are getting more air into the mix than the MAF is aware of and the ECU will not set the injector duty cycle properly. Then you run lean and the O2 sensors in the header collector tell the ECU "bad mix" and then it turns on your light. Check all your piping connections and the condition of the MAF. It might be fouled or damaged.

 

OK -

With your mods your car is running is REAL lean. Trust me.

Have you reset your ECU? If not, do the simple remove the negative terminal on the battery for 12 minutes and replace and see what happens. It'll take about 50 miles of driving for the computer to completely reset and adjust properly.

Other than that - either a flash or an AF piggy back and a tune.

Rick

 

+1. I have a Stillen intake/exhaust, Crawford cats/plenum and my car is very close to leanness.

Reseting the ECU is a good starting point as well as the pedal reset (turn car on -> wait 3 seconds -> punp gas 5 times in 5 seconds -> wait 7 seconds -> Press gas down for 10 seconds OR when the CEL starts flashing).

Do those first and if still a problem, look into an ECU reflash.

 

thanks a lot guys. I have reassebled the intake again and reset ECU today. The CEL are currently off.

 

Let us know what happens - these cars freak when they lean out and over richen...they have a sweat spot that is prety wide - 12.2 - 15.6.

If they get dry or wet - see ya!

Rick