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Car dies when I touch brakes
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Tilrak
New User
Jan 14, 2009, 8:52 PM
Post #1 of 4
(2841 views)
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Car dies when I touch brakes
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I drive a 98 Pontiac Bonneville, 3.7 I think, with 180k miles. My check engine light came on, and when the codes were read, it said there was a problem with the Mass Air Sensor or the Map sensor. Sometimes when it changes gears, it rides rough, and sometimes when I touch the brakes, the car will drop dramatically in RPM's, and even die....frequently. I've taken it to a repair shop, and he tried cleaning the Mass Air Flow Sensor, changed the PCV pipe or valve, and still no change. He thinks it might be the Crank Sensor, but can't get it to fail. Any suggestions? Thanks Josh
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Jan 15, 2009, 4:52 AM
Post #2 of 4
(2838 views)
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Re: Car dies when I touch brakes
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With it this sensitive to using the brakes I'd be checking for a power booster leak,
T
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Loren Champlain Sr
Veteran
/ Moderator
Jan 15, 2009, 5:09 PM
Post #3 of 4
(2829 views)
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Re: Car dies when I touch brakes
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Have you had the codes pulled since the MAF sensor was cleaned? If the MAF code comes back, it's probably the problem. The MAF sensor reads the temperature and volume of air flowing past it, relays that information to the PCM and delivers fuel accordingly. For some reason, don't see a lot of contaminated MAF sensors of GMs. Fords, yes. The MAP sensor detects engine vacuum. If it 'sees' a drop in manifold vacuum, the PCM assumes that you are under load, and dumps fuel. MAP sensors can't be cleaned. So, to add to Tom's suggestion, if you have a brake booster or anything else that is leaking vacuum, that can cause the MAP sensor to get faulty information. It doesn't always work, but you can take a scewdriver handle and gently tap on the MAF sensor. If the engine stumbles, it's definitely a faulty MAF. As I said, it doesn't always work. The crank sensor is a common failure on GMs, but usually, not an intermittent problem. If it goes south, the engine will not run. And, very seldom will set a DTC.
Loren
SW Washington
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Jeff Norfolk
Enthusiast
Jan 15, 2009, 7:20 PM
Post #4 of 4
(2824 views)
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Re: Car dies when I touch brakes
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Have the shop check the pins on the MAF plug. Most people will unplug the MAF to check the air filter and over time the plug becomes loose. Start the car and then wiggle the plug a bit. See if you can duplicate the symptoms.
Jeff
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