Throwing obd codes? -

4.6L (1996-2004 Modular) Mustang Technical discussions on 1996-2004 4.6 Liter Modular Motors (2V and 4V) within.

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Old 03-08-2017, 07:52 PM   #1
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Default Throwing obd codes?

Hello, this is my first post. I did some digging but didnt find anything of use so i made an account to give it a try. I recently got a 99 gt with 91k miles on it. All original except for a few things, in excellent condition. Im confused on a few things. I reset some codes the other day and theyre back. Theyre P0171 and P0174. They state that both banks are running lean. I also have a code for P0442, something about an evaporative emissions control leak. Could this one be related to the other two? Also, if it helps... the car has a brand new intake manifold, new cold air intake, new plugs, and new accel coil on plugs. i noticed a hose was pinched under the coil pack mounting bracket where it meets the throttle body. I believe it was the pcv hose? Its an elbow directly under the iacv. I replaced the hose with a new one and re routed it so it wouldnt pinch. I had a stumbling idle and occasional die after a warm start here and there. I dont know if it still exists or not because i havent drove the car since the new hose. But anyway, is any of this in relation to each other? Any help is appreciated. Thanks!
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Old 03-09-2017, 07:40 AM   #2
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lean codes usually indicate a vacuum leak or weak fuel pressure. If you have gone thru the intake side and verified no leaks exist, my next step would be to check fuel pressure/volume. A vacuum leak on the evap line could cause both issues, but its more likely you have two separate problems. Ideally, you should take the vehicle somewhere that has a smoke tester and you can kill two birds with one stone
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Old 03-10-2017, 06:36 AM   #3
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Generic codes set by the computer when it has reached its maximum threshold on the fuel trims table. It has added the maximum allowable fuel for the set parameters and is unable to correct a lean condition.

This code is typically caused by an engine vacuum leak or lack of sufficient fuel pressure. Probable causes include a clogged fuel filter, faulty fuel pump, an EGR malfunction, or engine vacuum leak/s. Other causes include a fouled or dirty mass air flow sensor, the use of high-performance cold air intake systems that require an oil charged filter element, positive crankcase ventilation system components that are drawing excessive vacuum or leaking, a bad oxygen sensor, an exhaust leak between the combustion chamber and the oxygen sensor, leaking, sticking, or inoperative fuel injector/s.
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Old 03-28-2017, 11:09 PM   #4
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Useless reply but kinda true with those codes:
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