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99 Grand Prix won't stay running
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tinkerer
New User
Mar 26, 2009, 4:51 AM
Post #1 of 2
(1544 views)
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99 Grand Prix won't stay running
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My neighbors' son has a 99 GP with 3.8l SFI. His car died on him, after driving for about 30 minutes, but did not set any error codes. He was very low on gas (read poor high school student) so I thought he may have sucked up some junk from the tank or lost fuel pressure if he was out. We put in about 5 gallons and it would not start (very foul smell coming from the exhaust when I tried to start it) I put an inline spark tester to see if it was an ignition problem and had spark. After I replaced the plug wire, the car started but died later that day at which point I had P0300 and P0171 codes. I pulled a plug and found they were in pretty bad shape so changed them as well as the air filter and fuel filter. That got rid of the P0300 but I still have the P0171 (has a small pd after the code also but I don't know what that means. I'm using an Actron pocket scanner that just spits out the codes) I disconnected the MAF sensor and the car will run but as soon as I plug it back in, the car dies. I made a jig to check the signal voltage from the MAF and it reads 2.5 volts all the time but not sure if that is a valid test since I really have to tweak the throttle to get it to run for more than 5 seconds. Any ideas where to start looking? As I said, he is a poor student so I don't want to start throwing parts at it. Thanks.
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Loren Champlain Sr
Veteran
/ Moderator
Mar 26, 2009, 5:06 PM
Post #2 of 2
(1534 views)
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Re: 99 Grand Prix won't stay running
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P0171 is a lean condition; This can be caused by a number of reasons. EGR stuck open, vacuum hose leaks, low fuel pressure, ect. But, it sounds like you are on the right track with the MAF sensor. You can try cleaning it, which sometimes will work. 99% of the time, if it runs better and fuel trims improve when you disconnect it, it's a bad MAF. I would recommend checking everything else, first, because those puppies aren't cheap...and you want to be right the first time.
Loren
SW Washington
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