I have a 2004 Pontiac Grand Prix GTP with an Overkill-Tuned PCM. The other day I had to disconnect my MAF Sensor because it was beginning to kill my engine at idle and I had to wait for a new one to arrive (tried cleaning it with no luck). My car still runs pretty good, much better than with it connected, but for some reason, my power brakes don't work now. I have to jam the brake pedal as hard as I can just to get the car to stop. I don't get any ABS, or Stability/Traction control error messages or anything though. It's like the brake pedal has an incredible amount of resistance. Sitting at a long red light or in traffic is ridiculous now. Why would it do that? I wouldn't think it would be related. I get the replacement sensor tomorrow so it SHOULD make this go away, right?

If you plug it back in, do the brakes go back to normal? This doesn't make the first bit of sense, either. Those two things have precisely zero correlation. But, humour me, plug it back in, and tell me if the brakes go back to normal.

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One Big Ass Mistake America

^^Big Ditto. Those 2 things have nothing to do with each other. The only possible thing I can think of is the idle is higher with the MAF unplugged and thus requiring more force from the brakes to remain stopped, but that is a HUGE long shot. Is the brake booster vaccum line still okay?

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Dubs:00 VW GTI VR6, Low and Slow 91 VW GTI 8v, Shave the Bay!! 91 VW Cabriolet 8v, bitch Basket
GP's:04 GP GT, Past now G-Ma's Girlfriend's 97 GP GT, "Project Pink Power"

Yeah plugging in the bad sensor doesn't affect the brakes and it shouldn't be related. Maybe just a weird coincidence. Where exactly is the vacuum line? I don't think I've ever had to mess with that before.

That's the brake booster line.

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Dubs:00 VW GTI VR6, Low and Slow 91 VW GTI 8v, Shave the Bay!! 91 VW Cabriolet 8v, bitch Basket
GP's:04 GP GT, Past now G-Ma's Girlfriend's 97 GP GT, "Project Pink Power"

Were you leaning on the top of the blower when you worked on the MAF? Bet you broke the plastic vacuum tree on top that runs to the brake booster. Ask me how I know this...... lol

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Mods include-
Pulley boys 3.2 pulley, 20* timing, HPTuned, pacesetters, SSIC, modded 1.9's, F/R STBs on Don Rome brackets, 255lph pump, ZZP billet rails, GXP catback
Best of 13.4 at 103.... 12's this year

I'm not surprised.
The MAF is one of the sensors used to decide where on the load curves to run the engine - timing,fueling,etc.
You've got an aftermarket PCM tune,so I don't know whether Will allowed for such things in his cal's - I'm guessing GM allowed for some "latitude" in their cal's...they usually do.
I'm not sure how much vacuum it takes to run the stock brake booster properly,but it sounds like you're running pretty low idle/cruise vacuum with the MAF disconnected.
Your underlying problem *may not* be a bad MAF,but could be a vacuum leak somewhere else in the system.
It wouldn't hurt to check.

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2005 GT owner [Non S/C] with a "big DIC".
Two years later and I still love the car.
Thanks Pontiac...Bleen is keen!

The vacuum tube was disconnected. I plugged it back in and the brakes were fine. Thanks for the tip. Definitely glad I didn't break off the T connector.

Hey great! Your situation is a good example on why I love this forum. You always get great feedback!

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2009 G8 GT -Sport and Premium Pkgs, Roto-Fab CAI, Cortex 93 Octane Tune, Billet Prototype Catch Can, BMR Front and Rear Sways, BMR RTAs, BMR Rear Cradle Bushings, BMR Steering Rack Bushing, GXP SW......and much more to come.

Score for easy fixes!!!!

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Dubs:00 VW GTI VR6, Low and Slow 91 VW GTI 8v, Shave the Bay!! 91 VW Cabriolet 8v, bitch Basket
GP's:04 GP GT, Past now G-Ma's Girlfriend's 97 GP GT, "Project Pink Power"

Good stuff.
Glad you got it sorted out.
Car driving better now too?

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2005 GT owner [Non S/C] with a "big DIC".
Two years later and I still love the car.
Thanks Pontiac...Bleen is keen!