canuck buick

unplugged, runs and starts good but for giggles decided to run with the MAF unplugged . Was surprised no difference,running , starting etc.
Do I need it

aklim

Did you just idle it or take it for a run? I'd be curious. I disconnected my MAP sensor and the car almost died. I can't see why you wouldn't need it unless the car is in limp home mode.

canuck buick

took it out for a run, burned out a couple times runs fine without it though the check engine light comes on

aklim

What code comes out?

canuck buick

dont' know just the light is on

aklim

Should get a scanner and see

John E

What year is this on? I will also be curious to know how gas mileage may be affected. Don't need a scanner to get codes for older C4s at least, just a jumper and a note pad for the codes.

aklim

True but diagnosis after that would be aided by a scanner.

zr1fred

MAF is not used in cold start or until engine warms up and goes into closed loop. The computer has a matrix loaded into it to run the engine in open loop.

aklim

Perhaps so but in post 3,he took it for a run

Tom400CFI

The MAF is used at all times.

Viper588

I know on most newer cars if there is no MAF detected the car will run on a default tune or map, that is tuned conservatively. The car will runa nd act normal other than a DTC and will will get poor gas mileage.

Tom400CFI

Newer cars use both a MAP and a MAF, so they have two ways to measure air consumption. Earlier cars don't; they are either/or. Only one way to measure air flow.

Cliff Harris

If the MAF is bad/not connected the ECM will use the TPS to guess what the air flow is.

I was troubleshooting a miss on my car and came home from work and started troubleshooting again. I found that the MAF was disconnected and I had not noticed any difference in the way it ran. I drove it to work and back, so there was a combination of surface streets and freeway driving. The miss turned out to be a bad plug wire, in case anyone is wondering...

canuck buick

Cliff when you plugged yours back in did you notice any difference?Just so people kknow when I took it out for a test run it never went above 150 degrees so I don/t know if it will be affected the warmer I run.My maf is a bosch.

WW7

Car is not going into closed loop without a maf sensor hooked up. You would be lucky to get 10 mpg ...If you hook up to a scanner you will probably see air/fuel readings way off spec without a maf...I wouldn't run the car without a maf sensor ,you need to hook to a scanner to see what's going on..Just because the car seems to run fine without a maf, doesn't mean it's safe to do so.....Running with unknown A/F ratios can cause engine damage..To answer your original question, if these cars didn't need a maf sensor , they wouldn't have one......WW
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Cliff Harris

Not true. The parameters for closed loop mode on my car are:

Coolant temperature > 40.7°C = 104.4°F
Engine run time > 300 seconds (cold) if startup coolant temperature < 58.5°F
Engine run time > 206 seconds (warm) if startup coolant temperature > 58.5°F and < 158.5°F
Engine run time > 50 seconds (hot) if startup coolant temperature > 158.5°F
Oxygen sensor reading between 0.195 and 0.686 volts for > 10 seconds

There's no "MAF present and working" in there. As I said earlier, the ECM uses the TPS to guess what the air flow rate is. That statement is based on examining the program code in my ECM. I'm still working on that. You can contribute your expertise by going to my ECM web page and helping me out:

http://home.earthlink.net/~cliff_har...5/BUA/BUA.html

WW7

It's my understanding if the maf sensor is not connected ( or not working) the car goes into "Limp home mode" , which means it runs off of the settings in the chip...Is this not true??.When my maf sensor went bad, I had no problem telling my car was not running correctly and on my way home the gas mileage sucked.......WW

Tom400CFI

Car ALWAYS run off the settings in the chip -that is the "tune"

Motor runs poorly w/no MAF because as stated above, ECM tries to estimate air flow off TPS and RPM which is a rough estimate.

Cliff Harris

In limp mode the ECM uses the resistor networks in the MEMCAL to determine injector pulse width. The microcontroller is held in RESET mode and does nothing. Everything is controlled by the FMD (Fuel Management Device) IC.

I believe the ECM also switches out of bypass mode and the ignition module manages the ignition advance curve, but I don't know for sure if this is true or not.