engine misfire

1999 MERCURY COUGAR
155,000 MILES
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BERRERIC
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1999 mercury cougar when trying to start acts like its only firing on two cylinders. After it starts eventually it idles really really rough fir about a minute then gradually gets better then car runs fine. What could this be?
Oct 14, 2012 at 9:17 AM
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KHLOW2008
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Do you have coolant losses and overheating issues?
The cold start does not seem to be working and this can mean a fault with the idle control system.
Is the Malfunction Indicator Light showing?
Oct 14, 2012 at 9:35 AM
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BERRERIC
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No coolant loss or overheating. I replaced the fuel tank about a week ago then all these issues started. I was driving when I went up a hill and car lost all power. Idled fine just no power under acceleration. The check engine light is on and its a p1131 code which is switch,sensor indicates lean.
Oct 14, 2012 at 1:14 PM
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BERRERIC
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Only thing replaced was the fuel filter and tank. The fuel pump is only maybe eight months old. Car while running has 48 psi fuel pressure. Doesnt seem to have fuel pressure when just turning the key on though.
Oct 14, 2012 at 1:25 PM
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KHLOW2008
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DTC P1131


DTC P1131 indicate air/fuel ratio is correcting rich for an overly
lean condition.
Possible causes are:

Fuel system malfunction.
EGR system malfunction.
Air intake or vacuum system leak.
Engine oil level too high.
Incorrect cam timing.
Restricted air cleaner.
Faulty PCV system.
Excessive internal engine wear.

Inspect engine for obvious defects in specified systems. Repair as necessary.

Oct 14, 2012 at 1:29 PM
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BERRERIC
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Why would this just happen after replacing the fuel tank? This code was there before the fuel tank was replaced. Car ran fine before.
Oct 14, 2012 at 1:41 PM
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KHLOW2008
  • ✓Experienced Mechanic
  • 41,812 POSTS
Maybe something was not done correctly when fuel tank was replaced. On the other hand the problem could be something new that just started.
Oct 14, 2012 at 2:57 PM
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