Well my CEL keeps coming back and I realyl don't know why.

02 Z06, stock with a Halltech Venom and SLP Loudmouths. I keep getting P1071 and P1074.

I reclamped the intake and made 100% sure there was no air leaks and then cleared my codes. It was fine for 2-3 days and today when sitting in the mall parking lot talking on my phone the CEL came back on and surprise, right and left banks are lean.

So now what do I do? This is a pretty stupid problem to have. This all started 1 day after I installed this intake and 20 seconds after I got gas.

Is there anyone who think I have a bad tank of gas?

 

No ... you don't have bad gas ..... (at least in the car) .....

Your switch to a CAI has caused the "problem".

Your MAF is seeing a different flow of air across the wires, and that changes the signal being reported to the PCM. That change causes the PCM to feed a lean mix to the cylinders, and it is so lean that the PCM can't compensate using the STFT (Short Term Fuel Trim) and LTFT (Long Term ....) parameters.

You can fix this two ways .....

1) Go back to your stock intake, or try another intake system.

2) Get a "tune" of the MAF table in your PCM.

Don't believe me ???? Real easy test .... put your stock intake system back on .... I GUARANTEE that the "lean" codes will not come back.

 

Nope not bad gas definitly your intake, this is actually a more common problem then people think. This happens on other cars as well, intakes flow too much air computer cant provide enough fuel to compensate i had this problem on my past car which was an 01 M3 after my intake install.

 

I get the same thing with a Vararam. Biggest issue when the filter is clean, not so bad when filter is getting dirty.

Mine only goes on when the car is at very light load, or even off the gas decelerating. Never under power.

Any concern, or just an anoyance?

 

Had the CEL w/ the Vararam, put the stock intake back on and had no more problems, do not care for CAI's.

 

I have a 2002 Z06 - Installed the same CAI and had chronic lean codes too. Rreturned the CAI - vendor refunded full amount.

Buit my own using a K&N ( as per directions posted somewhere here).

Funny thing-- the Venom moved the MAF to the rear to supposedly eliminate the lean codes. My homemade CAI has MAF in OEM location and no codes. The K&N appears to have the same size filter.

Return you CAI- or spend the $$$ for a tune. I just wasn't willing to spend more $$ for the tune than the CAI.

Good luck !

 

it just seems so weird that an intake can lean out so much that the ecu can't compensate. maybe if I go back to the stock airbridge with a vararam I can eliminate this problem?t

 

I have been having the exact same problem for nearly a year now. The ONLY thing I have aftermarket is a K&N filter.

I've checked all clamps, no leaks anywhere. Getting both banks lean.....even cleared everything out a few time by disconnecting the batt. etc....
I figure I'll finally get rid of it when I get headers and a TUNE.

 

I measured this change and on one of my cars was right at the max of 25%. A tune up of the pcm would be the best option using almost any aftermarket airbox.

 

Your airbox is causing turbulance around the MAF and you have undetected air sneaking by the MAF's heated wires. This undetected air is not being mixed with the proper amount of fuel. Either get the car tuned or put the stock airbox back on. I would probably just go back to the stock box.

 

If this is the case how would a tune help? If the air is undetected it seems like a tune isn't really going to make the MAF start detecting it.

 

You (and some other posts) are mis-understanding what is happening .....

The CAI is not flowing more (or less) air .... it is changing the WAY the air is measured. Let's take a simple shot of how this works ......

Let's design two intake systems .... one (called "A") flows the air VERY smoothly through to the MAF .... no turbulence and the air velocity is constant, whether measured along the sides of the air flow or in the center.

The other (called "B") creates a fair amount of turbulence and the air speed is faster in the center of the flow than at the edges of the flow.

So we now mount system A on a flow bench, and have the flow bench flow a known quantity of air through the MAF we want to calibrate. Let's just say that with a flow rate of 20 grams per second (a MAF measures the MASS of the air ... its weight) the MAF signal is 2000 Hz. We now plug into the MAF table of the PCM that a signal of 2000 Hz is 20 g/s ...... then we flow 30 g/s and let's say the signal is 3000 Hz .... we tell the MAF table that a signal of 3000 Hz means 30 g/s.

Now we install intake system B on the flow bench and we flow 20 g/s though the system. The MAF signal will be different because the turbulent air is gonna change the temperature of the wires ... aagain this is an EXAMPLE ... these are not real numbers ..... let's just say that at 20 g/s the signal is 3000 Hz .... in a NEW table we input that for the B system a 3000 Hz signal means 20 g/s.

OK let's just say that system A is actually the OEM system .... and you take it off your car and put system B (third party product) on the car. You HAVE NOT changed the MAF calibration in the PCM. The PCM still thinks you are using the system it was programmed for.

Now you're driving along and the PCM is getting a 3000 Hz signal from the MAF .... it looks that up and thinks that means the engine is getting 30 g/s of air ...... but the engine is ACTUALLY getting only 20 g/s ....... in this example the engine would run overly rich. We didn't change the amount of air going into the engine ... we "fooled" the MAF by changing the intake layout.

If we take the car to a tuner, and they "correct" the table so that a 3000 Hz signal is now equated to a 20 g/s reading ... engine will run perfectly .....

Now when GM layed out the software for the PCM, they knew that they faced two possible issues dealing with the MAF. First is manufacturing tolerances .... not every intake system and MAF are identical ... there is gonna be some variation car to car in what the MAF measurement is gonna be for a given air flow. The other issue is over time the "performance" of the MAF will alter. Dirt accumulates on the sensor wires and alters, very slowly, the way the MAF measures.

So GM built some "tolerance" into the PCM software to allow for these small car to car differences.

However, it seems that some CAI cause a bigger shift in MAF sensitivity than others. Also, if your MAF tolerances were already borderline, the new intake may push you "out of limit" and set the DTC.

So .... again ..... it is not that you are actually flowing "more air" ..... it is that the MAF is "reporting" an incorrect value. Don't forget at a steady 3000 RPM a stock engine is inhaling ROUGHLY 300 cubic feet of air per minute. That number doesn't change whether you have a stock intake, a Vararam, or some large plastic pipes you put together yourself. What can change is how the MAF measures that air.

 

This is true. I have been saying this for over 5 years and many people just don't seem to understand this.

 

I have a 04 Z06 and recently installed a Vararam intake. I'm also getting the same codes as Milan. The car seems to run fine but the check engine light really bothers me. I've decided to get some LG headers and a tune. Tired of fooling with this.

 

04 Z06 with Vararam and I'm getting the same lean codes.

 

Ditto for me. Go for a tune on the 28th I will let you know if it fixes it. I also have supermaxx ehaust system by the way.

 

Some tuning software and a wideband 02 sensor would be really helpful. I can't imagine making engine mods that affect AFR without these tools. The tuning software let's you "see" what is happening with your fueling so you can determine whether you are hitting the max % of LTFT/STFT causing a DTC. You can "tune" the MAF table for the change in airflow characteristics.

The tuning software is a great investment, for example, I had some headers installed and then noticed a slight miss at idle. I set the tuning software to scan for misfires. Sure enough, #3 cylinder was missing a little bit. I pulled the #3 plug and sure enough it had a cracked insulator.

 

UPDATE

Well I filled my car with Texaco 93 octane and my CEL went off. I ran the car normal and then pushed it hard to try to get the light to come back on. No CEL. ????????????????????????????

 

Good advice, would like to add a few things:

Need to obtain and learn how to use a datalogger. Log MAF FREQ, STFT, LTFT, RPM, TP, O2S11, O2S21, COM A/F

IDLE can easily be tuned using using STFT. In fact, that is exactly the percentage the maf is off. Make sure the A/C is off.

For WOT, you can use the o2 sensors. Stock is around around
907-916mv. Measured by WB, this is close to 12.7:1 A/F

Then smooth the data between top end and idle. A trick I use for WOT tuning is to load the car in 5th or 6th gear and floor it at given RPMs, such as 2500, 3,4,5 then check the voltage readings. This doesn't help closed loop, but given that you are still adjusting the MAF, it probably will when done. Datalogs of RPM vs O2 are very useful here.

If a wideband is avail, thats a plus, change the MAF until the A/F in PE vs RPM is the same as the wideband.

Take the car for a drive, test, then tune again if necessary.

 

See I've heard of this too, and mine didn't even come on until I bought a tank of gas at the local Indian reservation.