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OK to unplug MAF sensor and drive car?

11-25-2009, 12:50 PM
I have been trying to diagnose a problem on my '02 GP. My mechanic thinks it may be the MAF sensor, but isn't sure. My question: can I unplug the MAF sensor and drive the car, for the purpose of seeing if the symtoms change?

the symptoms: Driving the car under load, it hesitates. Classic feel that you get when spark plugs start going bad. I installed new double platinum plugs, and got a replacement set of GM wires under warranty, and put everything in, it was looking great. Unfortunately, I didn't fix anything.

I can easily reproduce it doing 20mph up a steep hill near my house. It also lunges forward, falls back over and over on hills.

If I unplug the MAF, and it rides smooth, I'm thinking that might be the info I'm looking for.

11-25-2009, 12:56 PM
I've never done it myself, but I've seen the guys on here suggest doing that several times. Unplug the MAF and if it drives better = bad MAF. I'll let them speak for themselves, but I'm thinking you've got it nailed. Have you tried cleaning the MAF to see if that improves anything?

11-26-2009, 02:07 AM
ran with mine unplugged for a week while I waited for my replacement to ship.

11-26-2009, 02:08 AM
or swap it with the one on your 08 for diagnosis. If the 08 even still has one.

11-30-2009, 06:59 AM
GM MAF test procedure: while engine is running tap the top of the MAF sensor with screwdriver handle several times, and if the idle changes for a second or two replace the MAF.

12-05-2009, 08:44 PM
Nothing bad happens. The downside is the PCM has to "lookup" fuel pulsewidth values from a table based on ERPM and TPS (kinda reverting to TBI technology except with more injectors and sequential fire). I think while it doesn't hurt durability or power it does not run as efficiently.

The idle also seems to be higher with MAF disconnected in order to keep it stable.

12-11-2009, 12:08 PM
I may be wrong, but doesn't that put a lot of strain on the EGR if you keep running it like that?

12-11-2009, 07:18 PM
Um, strain on the EGR?

Keep in mind that EGR is used for two purposes...reduce flame temps to combat NOx formation and it also is a fuel economy "tool" as it basically displaces air/fuel mixture. The tradeoff is it is a "diluent" to the swirling mixture and obviously reduces power.

In any case, my thoughts are if the engine can't closely regulate air/fuel (ala the MAF sensor disconnected - hence running in "backup mode") the strategy would be to *lessen* the use of EGR. Basically an over-excursion into EGR is recipe for stumbling, misfires, and worst-case flame-out (stall).

Also I'm not aware of any "strain". Its just a solenoid valve commanded to be open or not.

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