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HDGENE, Ford Senior Master/Diesel/Trans
Category: Ford
Satisfied Customers: 5491
Experience:  25 years Auto experience, Ford ,GM, Chrysler, Asian & European
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Ford F150: I have a 2004 F150 with 5.4 Triton which I bought

Customer Question

I have a 2004 F150 with 5.4 Triton which I bought last winter. It has about 130k miles. It always started fine when cold, but sometimes when warm, after a short stop, it would cough and stumble and not start. I would have to pump the gas pedal while engaging the ignition in order to get it to start. Last week while starting it warm, there was a loud bang, almost like a backfire, from under the hood. Then a billow of smoke or dust came out of the grill at the far left (drivers) side. I was able to restart it afterwards, but soon the Check Engine Light came on. The engine ran fine at speed, but when stopping at a stoplight the engine rpm would slowly decrease to a lower and lower idle, until when it reached about 500rpm the engine when die. When the trouble codes were read they returned P0171 & P0174: system too lean in bank 1 & 2. I suspect a blown gasket in intake manifold. Do you agree? More importantly, do you have any idea what may be the cause so that it can be addressed to prevent a reoccurence?
Submitted: 2 years ago.
Category: Ford
Expert:  HDGENE replied 2 years ago.
Hello, these engines have a few mechanical issues between base engine oil pressure and the variable camshaft phasers it uses to adjust camshaft timing as well as valve train issues or burnt valve seats. Its indicating both banks are running lean. So basic checks including engine compression and engine vacuum along with fuel pressure and oil pressure will tell you for certain what type of engine problem you may have. Also on the drivers rear of the lower intake manifold is the vacuum supply hose to the vacuum brake booster. its a good possibility this vacuum hose is disconnected. Its a 90 degree tube that is not at all easy to access to in plain sight at the back of the drivers side cylinder head.Metal tube sits on the valve cover from the booster to the tube and back to the lower intake. Make sure that is connected. It can cause these types of issues as well.

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