93 F150 rough running

Discussion in 'The Garage' started by Honda55, Dec 9, 2012.

  1. Honda55

    Honda55 Been here awhile

    Joined:
    Feb 21, 2010
    Oddometer:
    197
    Location:
    Quakertown, PA
    I just picked up my grandfathers 93 F150. it has the 300 inline 6. it runs real rough right now. It has been sitting for the past 2 years. Before he let it sit, he got it all tuned up (new distributor cap, plugs, and wires.) I just bought plugs to replace them since they werre fouled. I havent had a chance to put them in since its raining. Right now, it will start sometimes and idle rough. Any input from the mechanics??

    Thanks in advanced,
    Andrew
    #1
  2. eepeqez

    eepeqez Long timer

    Joined:
    Sep 8, 2009
    Oddometer:
    2,072
    Location:
    Melbourne, Australia
    How old is the fuel in the tank?

    My last car was converted to run on LPG (propane), which is a common and much cheaper mainstream fuel here.
    Some injected motors tend to clog up their fuel injectors when running on LPG; my car was particularly bad, so I just ignored the issue and never ran it on petrol (gasoline). After all LPG was under half the price, so why would you?

    Shortly after I got my current car and converted it to run on LPG, I decided it needed a second LPG cylinder and discovered that, of the hundreds of sizes on the market, the cylinder in the old car was the largest that would fit in the available space. The government had just started a subsidy program for LPG conversions (I missed out!) and new tanks were very difficult to find so I took the tank out of my old car and fitted it to my new car.

    This left me with a car which in principle would run on petrol, except the injectors were utterly clogged, so I bought a fuel rail and a set of injectors at the wreckers for next to nothing and fitted them.

    Here's the relevant bit...
    It ran like a dog. Rough idle, flat spots everywhere, just one very unhappy motor.

    So I went out and bought a distributor cap and leads, and while I was out, I put some more petrol in it since it was almost empty.

    Then I returned the cap and leads on my way back home again....

    When I had a think about it, I realised that any petrol in the tank was at least two or three years old. Once I added fresh petrol it was fine.
    #2
  3. Wasser

    Wasser Spilt my beer

    Joined:
    Oct 31, 2009
    Oddometer:
    5,256
    Location:
    Colorado
    Before you start throwing parts at it, go pick up an old school engine analyzer and, learn what the readings mean.

    [​IMG]

    LINKY
    #3
  4. GreaseMonkey

    GreaseMonkey Preshrunk & Cottony

    Joined:
    Jun 16, 2006
    Oddometer:
    5,434
    Location:
    The only county in Illinois with no train tracks
    Does this have a carb or fuel injection? Dunno about 93 and too lazy to look it up right now.
    #4
  5. H96669

    H96669 A proud pragmatist.

    Joined:
    Nov 20, 2009
    Oddometer:
    4,750
    Location:
    Hiding off Hwy 6, B.C.
    Before you go too far...it may be sucking up water/crap from the bottom of the tank. If it was left sitting for a while without a stabilized full tank of gas, that may just be your problem.

    My 83 Toyota "bush car" that I leave sitting for months and into which I dump all my "over 3 months old" fuel was doing the same recently, to the point of the moisture/crap finally plugging up the fuel filter. New fuel filter and because there is no Ethanol in our fuel I dumped some Methyl Hydrate in the tank.It is running much better now.:wink:
    #5
  6. concours

    concours WFO for 41 years

    Joined:
    Dec 2, 2008
    Oddometer:
    5,454
    Location:
    Kensington, NH USA
    Pump out and fresh fuel it. Run Seafoam magic elixer through it. The fuel injectors may be clogged from sitting so long. As mentioned above (cryptically) check compression to see if there is a stuck valve. (Yes, we know that's a vacuum gage shown) Do your assignment, report back in a timely fashion.:D
    #6
  7. Honda55

    Honda55 Been here awhile

    Joined:
    Feb 21, 2010
    Oddometer:
    197
    Location:
    Quakertown, PA
    Well I got impatient and put the new plugs on in the rain and it purrs like a kittens now. Sea foam and plugs was the answer:deal. Thanks for all the help!!!!!
    Cheers:freaky
    Andrew
    #7
  8. concours

    concours WFO for 41 years

    Joined:
    Dec 2, 2008
    Oddometer:
    5,454
    Location:
    Kensington, NH USA

    Good job!:freaky
    #8
  9. pennswoodsed

    pennswoodsed lizards,bugs and me

    Joined:
    Jan 20, 2007
    Oddometer:
    798
    Location:
    Reading,Pa
    1993 f150 4.9 is injected ,#5 injector lays at a spot(in theory) where crap comes out of suspension . Fuel filter ,(in practice) is out of sight and no fun to change . Glad it runs better.
    Regards,Ed
    #9
  10. pennswoodsed

    pennswoodsed lizards,bugs and me

    Joined:
    Jan 20, 2007
    Oddometer:
    798
    Location:
    Reading,Pa
    1993 f150 4.9 is injected ,#5 injector lays at a spot(in theory) where crap comes out of suspension . Fuel filter ,(in practice) is out of sight and no fun to change . Glad it runs better.
    Regards,Ed

    ps 150k treated poorly ,250k if cared for
    #10