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Old 09-29-2012, 10:14   #1 (permalink)
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99 cougar engine problems help please

I have a 99 cougar 142k auto v6 the car has engine codes p0171 p0174 p0420 it is leaking gas from the intake manifold will upper and lower gaskets fix this? Also I have a SRI on the car and I tried cleaning the maf yesterday and now I get a burning smell and if I rev it up to about 3-4k rpm when I release it kinda back fires or I hear like a pop sound is this the maf bad? Any suggestions will help
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Old 09-29-2012, 10:24   #2 (permalink)
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Re: 99 cougar engine problems help please

It sounds like your MAF maybe working better than before. It sounds like your codes are being caused by your O2 sensors. If your system thinks its running lean, it can be dumping more gas than necessary and running rich. Be advised that if you let this problem persist, you may end up plugging your cat.
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Old 09-29-2012, 10:50   #3 (permalink)
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Re: 99 cougar engine problems help please

How do I know witch o2 sensor to change? Could that be what is causing it to leak gas?
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Old 09-30-2012, 06:18   #4 (permalink)
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Re: 99 cougar engine problems help please

You brought up another symptom that I overlooked in my armchair diagnostic tool. You're intake manifold should be under a vacuum, so gas shouldn't be leaking out of it, which means you probably have a severe vacuum leak, unless the gas is actually leaking from the fuel rail. I would check pressure at the fuel rail as well as check vacuum on the manifold. P0171 and P0174 indicate both left and right sensor too lean, before replacing them both, I'd verify that they're getting power and that they're sending a signal back to the PCM. P0420 is more of a catch-all that says something is wrong in you're system.

This may help: Ford OBD-II Trouble Codes

And if you need a schematic: AutoZone.com Repair Guide Image
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Old 09-30-2012, 08:12   #5 (permalink)
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Re: 99 cougar engine problems help please

Okay thanks again I will take some of it apart and look for a vacuum leak what is the easiest way to check fuel pressure at the fuel rail? And could a after market intake it's an Sri cause this problem too as far as being to lean or do you think it's more the vacuum leak and the leaking gas
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Old 09-30-2012, 11:47   #6 (permalink)
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Re: 99 cougar engine problems help please

You can by a pressure gauge at most automotive stores that screws onto the service port on the fuel rail. It isn't intended to be left in place, but it can tell you the running pressures at the fuel rail. The SRI shouldn't have an affect other than allowing more air to be available for the engine to use, the throttle body will regulate how much passes and should keep the mix at the right ratio. The leaking gas puzzles me, check the fuel pressure regulator, see if it's corroded and/or leaking.
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Old 10-01-2012, 10:27   #7 (permalink)
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Re: 99 cougar engine problems help please

It seemed to not be leaking but when the car runs has leaks from the left side by the belts. Leaks from the intake plenium but it leaks worse since the maf was cleaned any ideas?
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Old 10-01-2012, 17:45   #8 (permalink)
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Re: 99 cougar engine problems help please

So it's leaking once the car is shut off? If this is so, then it's got to be the seals on your fuel rails.
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Old 10-02-2012, 15:02   #9 (permalink)
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Re: 99 cougar engine problems help please

No I'm sorry it's leaking gas when running more so at idle I like its an injector or I ring
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Old 10-04-2012, 17:20   #10 (permalink)
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Re: 99 cougar engine problems help please

It still has to be coming from the fuel rail assembly, even if you have a vacuum leak, the manifold is still under a vacuum and won't leak gas out.
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