i've disconnected my MAF for testing purposes but was told that the PCM will go into limp-home mode and ignore almost all of the sensors. is this true? car seems to run a little better with it unplugged.

 

It goes into speed density mode. Runs off the MAP sensor and pre determined fuel tables. If it is running better that way, I would check your MAF to make sure it is clean.

 

No, it won't go into limp-home mode. That a urban myth. Mine runs better with it unplugged as well.

The MAF is a freakin scam in my opinion. The more I learn about the MAF the more sure I am that we are better off without it.

- Makes it easier to tune
- 93's ran stronger without it
- Most of the faster N/A LT1's run without it.

With my new buildup I am going dual intake, and !maf.

 

What kinda dope are you on buddy??? You unplug the MAF and your car will go into open loop and won't use any of the values from the many sensors on your car. Explain to me how predetermined tables in the PCM make your car run better than when the PCM gets realtime values from the sensors. That was a really ignorant thing to say...

Do you really drive around with your MAF unplugged on purpose? Your car would not even idle right...

"The MAF is a scam" Riiiiiiiiiiiiiiiight, and pigs fly right? Oh wait wait, it must be a huge GM conspiracy because after countless hours of research GM engineers decided to knowingly put something in that makes the car run worse right??? Do whatever you think is right, I'm done here.

 

my car idles good both with the MAF unplugged and with it plugged in, and out of gear it seems to idle better with the MAF unplugged.


does the car go into open loop with the MAF unplugged? i keep getting different answers from different people and i'm confused.

 

You should get your facts straight before you come on here and flame someone that obviously knows more than you and is just trying to help.

You = go learn about MAF and come back

kthanxbye

 

there is no such thing as "limp mode".

the reason a car might run better in speed density is because the MAF sensor needs replaced. my personal experience with them is that the sensor is very sensative therefore it doesnt accurately measure incoming air when you start pushing 50k miles. i remember a member once saying he worked for mercades i believe and that the MAF was one of those things he replaced more often... i know its not GM but im sure they are all constructed nearly the same.

 

It's not flaming when I'm the one correcting you. I mean please don't tell me that my words hurt your feelings or something or that me pointing out your ignorance made you think I was flaming you. You are saying that running in open loop with no sensor data being collected makes a car run better, sorry I don't agree with that and I don't hesitate to share my feelings. I'm sure in a couple freak cases you would be right but that's not the norm.

Also, please name some people and describe their setups with a stock PCM that don't use a MAF sensor and are not 93's please I want to know out of curiousity since you mentioned it.

I'm curious, what makes you believe the MAF is a scam? I'd like to know, maybe if you come with some valid points I can agree with you but what you said was not believeable.

 

Wow.
This is not something worth getting your panties in a bunch over.
The Speed density systems need more tuning with mods because they are not able to compensate the way a MAF system can.
Up to a certain point its better to go with MAF in my opinion.
Now when you get up there in the HP numbers and you start running a system like the ACCEL DFI you tune it with a laptop and the need for MAF is eliminated, it also becomes a restriction at high HP levels.
A MAF system is a little more flexible when used with the GM PCMs
It can measure the exact amount of air that is coming in instead of guessing the way speed density does.

 

That's exactly what i thought.

 

What evidence do you have that the PCM drops out of closed loop and ignores all the sensors when you disconnect the MAF sensor? It appears to me, based on my experience, that when the MAF is disconnected, the PCM defaults to speed-density tuning. After all, what other reason would there be for a volumetric efficiency (VE) table? It appears to me that the PCM operates exactly the way it was operating before the MAF was lost, with regard to closed loop, and sensor input.

Speed-density requires more tuning than a mass-air system. When operating correctly, the MAF sensor directly measures the mass of air entering the engine. That's all it needs to know to calculate the reqruired fuel. Speed-density, on the other hand, depends very heavilly on the VE table, and that can only be accurately programmed based on extensive dyno testing. And, any changes which affect volumetric efficiency requires a new series of dyno runs to re-measure VE. That simply isn't necessary for a mass-air system.

And the "urban legend" is that for any minor glitsch the PCM experiences, it goes into "limp home" mode. It doesn't. There are a variety of alternative methods used to circumvent the problem, depending on the specific problem. However, there is in fact a "limp home" mode provided for the case where the computer and or most of its inputs are lost. But I doubt many people have actually experienced it.