500rpm stumble
Mar 20, 2009, 09:29 PM
#1
500rpm stumble
Ok I'm sick and tired of this, if I rev the engine in idle 3k and up the rpm will drop to about 500 and it will start to stumble..I can see black smok from tail pipe indicating a super rich condition..I had an lm1 on it tonight and it showed lean as hell. An old log of the problem showed injecors were droping off the chart 0v to 4.6 v so super lean to rich swings..
Before I changed to the bbk full and 720 injscaled to 636. The problem was almost non existant..NOW ITS BACK. Problem was deminished when I cleaned the **** out of the IAC motor.
I am pretty sure that my intake pipe is the cause of it (crappy weapon R) I would ditch it but I have a sneaky peat water/meth M2 noz. and a custom in fender intake. Basically would rescaling the maf in the 500 range where the stumble is help it out? And does anyone know how to do this? I also have lean idle and lean cruse enabled with the open loop closed loop switching points
Or should I just ditch stock maf and go Maf translator?
Before I changed to the bbk full and 720 injscaled to 636. The problem was almost non existant..NOW ITS BACK. Problem was deminished when I cleaned the **** out of the IAC motor.
I am pretty sure that my intake pipe is the cause of it (crappy weapon R) I would ditch it but I have a sneaky peat water/meth M2 noz. and a custom in fender intake. Basically would rescaling the maf in the 500 range where the stumble is help it out? And does anyone know how to do this? I also have lean idle and lean cruse enabled with the open loop closed loop switching points
Or should I just ditch stock maf and go Maf translator?
Mar 20, 2009, 10:18 PM
#3
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It is all about the MAF scaling for idle. You need to get the car to idle at less than 50Hz in order for the LTFT Low to adjust and allow for better idle. Cams, hard pipes, and higher flow filters all cause this issue.
From the sounds of it your injectors are most likely scaled correctly. Do a log and figure out what Hz you idle at (you will need to convert the MAF scaling to read in Hz). Then if your LTFT and STFT are both positive you need to raise the MAF Hz value that it idles at, the opposite is true for negative LTFT and STFT. You are mostly concerned with the LTFT Low for idle.
The problem is though, until you get the Hz below 50 at idle....no dice in the above method.
I found that smoothing out air flow after the MAF helps to lower the Hz value at idle. I did this by putting on a 3inch rubber coupler onto the MAF output side and inserting it into the hard pipe and clamping it as usual. This smoothed the MAF signal and allowed for LTFT Low to adjust accordingly. Then scaling the MAF is easy.
From the sounds of it your injectors are most likely scaled correctly. Do a log and figure out what Hz you idle at (you will need to convert the MAF scaling to read in Hz). Then if your LTFT and STFT are both positive you need to raise the MAF Hz value that it idles at, the opposite is true for negative LTFT and STFT. You are mostly concerned with the LTFT Low for idle.
The problem is though, until you get the Hz below 50 at idle....no dice in the above method.
I found that smoothing out air flow after the MAF helps to lower the Hz value at idle. I did this by putting on a 3inch rubber coupler onto the MAF output side and inserting it into the hard pipe and clamping it as usual. This smoothed the MAF signal and allowed for LTFT Low to adjust accordingly. Then scaling the MAF is easy.
Mar 21, 2009, 09:09 AM
#5
I converted the maf to read as Hz last time I addressed this. the hz was @ 50.32 at the stumble..I will log it again to see what it is. The voltage lat. were done as well, I'm pretty sure that they are good..they are form Brian @ GST.
How would a misfire read as a lean condition? The idle at the stumble is pretty rough but corrects itself after a few seconds. I do not throw any codes. I'm not disreguarding it, just how does it work so I can check it out.
Thanks for the input all..with your help and luck I hope I can get this thing fixed.
How would a misfire read as a lean condition? The idle at the stumble is pretty rough but corrects itself after a few seconds. I do not throw any codes. I'm not disreguarding it, just how does it work so I can check it out.
Thanks for the input all..with your help and luck I hope I can get this thing fixed.
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