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1999 Ford E150 5.4L V8 P0171 help and other questions

Home Forums Stay Dirty Lounge Service and Repair Questions Answered Here 1999 Ford E150 5.4L V8 P0171 help and other questions

This topic contains 2 replies, has 2 voices, and was last updated by Jon -Paul Stone Jon -Paul Stone 12 months ago.

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  • #895884
    Jon -Paul Stone
    Jon -Paul Stone

    So I bought me a 99′ E150 with the 5.4L seller up front told me it was throwing codes so I brought my scan tool and low and behold the famous P0171 “Bank One Too Lean”. Long term fuel trims pegged at 25. It drove okay for having 300K on it. He told me he had his guy look at it and the code was due to vacuum leak and they wanted a few hundred bucks to fix it but since he was getting rid of it he did not want to put the money into it. It had also passed smog just 2 months ago. I talked him down on the price a bit and pulled the trigger.

    Got it home and pulled the engine cover off and right away I see a big chunk of vacuum hose missing sucking air. I fixed that and fuel trims went from 25 to between 10-14. For good measure I smoked the engine today and the only other leaks I could spot was coming out of the PCV elbow so I replace that. There is also a thin small diameter vacuum line that has broken off from somewhere its attached at the top of the engine behind the throttle body(maybe the HVAC but maybe also the EVAP purge or IAC) but for the life of me I cannot find where. Its RED and smoke did come out of it when I smoked the engine. I have just capped it for now. Also replace the fuel filter for good measure. Waiting to see if the MIL light will return but while I was working on that I noticed something else…

    After getting the van home aside from looking for vacuum leaks I changed the oil and filter. Castrol Edge High Millage 5w30 and I dumped half a quart of Marvel Mystery Oil in the crank case with 5.5 of the motor oil. First time using MMO figured what the hay could not hurt. Now I am getting white smoke from the tail pipe and nasty exhaust fumes. I did a combustion gas detection test on her and that was negative so seems like its not the head gasket. Would the MMO cause this white smoke? The smoke it mostly on cold start I have noticed.

    Any advice, input of anything at all would be much obliged. I need this van to last me hopefully a year or two till I can get my business of the ground and upgrade her. Thanks friends.

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  • #895885
    Nightflyr *
    Richard Kirshy

    I’ve been using MMO in my oil for a long time.
    Excessive tail pipe smoke has never been a issue.
    Considering the age and mileage of this vehicle …
    A couple of thoughts:
    A engine with ~ 300,000 miles is going to have a certain amount of varnish and build up inside the engine which actually helps seal it.
    Now depending on how it was maintained in the past ..
    MMO will start to clean out some of that which may be the cause of the smoke.

    Is the smoke constant even after the engine is at operating temp?
    White smoke on a cold engine start up at first is common.
    But if it continues well after the engine and exhaust is up to temp is another story.

    As to your missing vacuum hose, I would suggest researching the vacuum systems on that engine or get a service manual to help.

    Jon -Paul Stone
    Jon -Paul Stone

    No smoke is not constant mostly on cold start and dissipates after she warms up. As far as the vacuum leak yea I have been looking even on Pro Demand and not a lot of good info anyway on where all these vacuum lines connect to or come from just gonna have to keep looking. In the mean time she is running and she is better than she was so I guess there is that.

    Thank you friend.

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