BigBadWhitey

iTrader: (3)

Anyone know how this is done? After some modifications on the car, with the maf plugged in it wont idle worth a damn (see: it fluctuates from about 800-1300 back and forth rather quickly and increases in amplitude), but at WOT its right on the money for fuel and getting little to no knock retard. When i unplug the RPM it idles right at 900 rpm.

Any ideas?

ThoR294

iTrader: (6)

"after some mods"

What did you do? Stock MAF is good for most applications... try cleaning it

ahritchie

iTrader: (1)

Yea, you should not have to calibrate anything at all with the MAF, how old is it? Did you remove the screen? (A no-no.) I have a stock replacement Cardone MAF that works just fine on my 383 setup. They do go bad eventually....

BigBadWhitey

iTrader: (3)

Its got a procharger on it with low boost (3psi at around 5k rpm)
Its not the maf itself, as ive used two different ones on there with the same result.

96capricemgr

iTrader: (1)

The MAF calibration is done in the pcm. The MAF sends a fequency to the pcm and he pcm is programmed as to how many grams of air per second a frequency corresponds to.

Has the car in it's current modified state ever run right. Was the tuning properly addressed?

BigBadWhitey

iTrader: (3)

The frequency corresponding to grams/sec, there are four tables for that used by the PCM right? Those are the ones that im looking at and are 100% unmodified from the stock values. Thats whats making me believe the calibration is the area of concern.

The car runs right from a driveability perspective, its just the idle that is off. The tune was done by Madtuner (something like that, it was over a year or so that it was done) and when logged and asked about it he said everything in the tune looked ok in relation to the datalog.

I have no quarrels with the tune from that aspect of things, im just trying to figure out the source of the idle issue. With the MAF unplugged the car idles just fine, which lead me to believe it was the MAF itself. For that reason i tried another MAF which caused the same issue, leading me to believe it is an aspect of its calibration.

96capricemgr

iTrader: (1)

If the MAF is stock and the intake track nothing goofy, then stock MAF tables seems reasonable. Are you sure there are no vacuum leaks? Stock MAF.

What is done to the engine to cause a 900rpm idle to be appropriate?

BigBadWhitey

iTrader: (3)

Maf is stock, the intake track is fairly standard intake pipe and silicon couplers. I havent been able to locate any vacuum leaks, and the maf is stock. If there were leaks, would it fluctuate in SD mode as well?

900 is what i recall it being on the Tach, but the datalog shows mid 800rpms with the MAF unplugged. The car is an m6, it has 42lb injectors, full exhaust and the procharger.