Need help on codes, what to replace first.
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Need help on codes, what to replace first.
96 F150 4.9L have four codes popping up at the moment was looking for help on best approach. P0171 (system too lean bank 1) P0174 (system too lean bank 2) P0443 (Evaporation system purge control valve circuit) P0385 (Crankshaft position sensor B circuit). When i got the codes read at auto zone the print out said they could all be symptoms of my fuel pump going out. Whats going on with my truck atm is a very rough idle until its warmed up then it goes away. Tell warmed up it was a flux of about 2-300 rpm. Also when looking up parts they said my engine doesn't have a crankshaft position sensor. Basically wondering if I should just start with the fuel pump replacement or if the symptoms could be from the purge valve. Thanks for taking the time to read this, im a super novice when it comes to most things mechanical my knowledge is limited to what I can youtube!
Fleet Owner
Joined: Oct 2005
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From: Kentucky
Since you have lean codes for Bank 1 and Bank 2 it could be a fuel supply issue. Could also be a dirty/faulty MAF sensor. Verify the fuel pressure and clean the MAF using an appropriate cleaner. P0385 indicates a problem the the Misfire Detector, which your truck does have. There is a tone ring on the harmonic balancer and a sensor mounted to the timing cover. This sensor is used to detect a misfire only. It has nothing to do with the firing the spark plugs/injectors.
Your Vapor Management Valve (VMV) code P0443 can wait until you verify the fuel pressure is good and clean the MAF. On the V8 trucks I have seen P0443 pop up then find the computer (PCM) is bad. Let's not go there yet....
Welcome to FTE!
Your Vapor Management Valve (VMV) code P0443 can wait until you verify the fuel pressure is good and clean the MAF. On the V8 trucks I have seen P0443 pop up then find the computer (PCM) is bad. Let's not go there yet....
Welcome to FTE!
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Checked fuel pressure. With just key turned not running was at 12 psi, engine running held at 48 psi. Checked mass air flow other day didnt need to be cleaned. Also had to replace alternator this week, connection was completely burned off to bolt. After the replacement truck ran great for about 24 hours now its back to the same symptoms as before. Was wondering if there could be a connection issue. Curious for other tips, thank you.
Fleet Owner
Joined: Oct 2005
Posts: 20,789
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From: Kentucky
48 PSI at idle with the vacuum hose attached is good. Did the fuel pressure rise if you blipped the throttle? Same for when removing the vacuum hose from the regulator? It's best to place a load on the engine to see if the fuel pressure rises or drops. It should rise....
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