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7.3 misfire?

Discussion in 'Ford Trucks' started by Shade Tree NJ, Dec 10, 2014.

  1. Shade Tree NJ

    Shade Tree NJ Senior Member
    Messages: 202

    Have an 03 7.3 with 120,000 miles on her. A handful of times in the last 2-3 weeks she has basically "coughed" or almost died then catches itself at a light or stop. Haven't checked for codes, happens real intermitently, just want to catch it before gets worse. A buddy who is 50/50 on diesel knowledge said was it misfiring but I don't know for sure.
  2. Dogplow Dodge

    Dogplow Dodge PlowSite Veteran
    from NJ
    Messages: 3,699

    I don't own a 7.3, but I get Diesel Power mag and read through some of the tech articles from time to time. (and I stayed in a Holiday Inn Express last night)

    So, one of the thing's I've heard about is the CPS (crank Position sensor) tends to go bad, and can cause either a no start,or a rough run . I found a good site that has an entire FAQ section on them, if you want to review it. Once the CPS gets changed, the problem tends to stay away until the next time you need to change it again.... sometimes never. 1/2 hour or so to switch it out from the article I read.

    Cold weather, like it's been, I would first replace the fuel filter and put Power Service Red bottle in the tank, and filler up. I had my mitsu gel inside the fuel filter housing last year, and now I run that Powerservice white bottle anytime it's going to be cold. Don't want to relive that again.

    Hope this helps. http://www.thedieselstop.com/forums/f47/
  3. fatheadon1

    fatheadon1 Senior Member
    Messages: 406

    Check the oil level my buddys 7.3 would do that when it got low on oil because the injectors are fed off the high pressure oil pump
  4. Sprag-O

    Sprag-O Senior Member
    Messages: 220

    CPS or Fuel delivery... No coils, plugs, wires to worry about.
  5. Sawboy

    Sawboy PlowSite.com Addict
    Messages: 1,700

    CPS is likely culprit
  6. Shade Tree NJ

    Shade Tree NJ Senior Member
    Messages: 202

    Going tom top by auto zone or advance tomorrow or Thursday when get a few free min and have them scan it to see if any codes.

    Will swap out filter, changed it about 5k miles ago but a cheap fix, doubt that lucky!

    Usually use the dark gray bottle of power servicd every few tanks.

    Oil is good, checked twice weekly as has a leak from oil pan ( to much $$ to swap out )

    I believe cps was replaced about 2-3yrs/25k miles ago, but again for cheap fix worth the few $$ to see if fix. Again usually not that lucky.
    When cold, won't start in morning w/o being plugged in. Not sure if related or not
    Thanks for the quick replies and cheap fix tries (under $75 and some time)....will keep you posted
  7. Plowtoy

    Plowtoy Senior Member
    Messages: 929

    I think that should help ^^^^^ Worse case, you could have a failing IDM (injector driver module), but usually, those are all or nothing when they fail
    Last edited: Dec 12, 2014
  8. plowguy43

    plowguy43 PlowSite Fanatic
    Messages: 5,281

    OP - In the order I listed below is most likely what is wrong and/or what you should check/do first:
    #4 would possibly be a bad injector or harness has frayed. Make sure the oil is definitely full though or they won't fire.
  9. Mark Oomkes

    Mark Oomkes PlowSite Fanatic
    Messages: 13,256

    Wanna bet? See #3

    Anyways, as the others stated:

    1) Oil

    2) CPS (should be codes if this is causing it)

    3) Injector wire harness. The connectors become brittle from heat over time and cause intermittent runnability issues. This is a known issue.

    4) Then something else, like IDM or GPR. A bad GPR is going to cause a hard start issue, not a runnability issue once it is warmed up.
  10. plowguy43

    plowguy43 PlowSite Fanatic
    Messages: 5,281

    If replacing the GPR (Glow Plug Relay) go to a Fisher/Western dealer and buy a solenoid from them for the plow. Its a much beefier round style relay that is much more reliable. My truck went from barely starting on cold days (requiring multiple cranks & glow plug cycles) to a one cycle and starting first try.
  11. dieselss

    dieselss PlowSite Fanatic
    Messages: 11,395

    Did you get any codes? Till.he replies, were all spinning wheels
  12. tjctransport

    tjctransport PlowSite.com Addict
    Messages: 1,390

    www.ford-trucks.com is a very good source for troubleshooting issues with fords.

    there are way too many possibilities for problems to figure out without knowing what codes are present.
    if it is misfiring, it may have a soft code that will not turn the CEL on.
    a very common problem with these trucks is the under valve cover harness.
  13. Shade Tree NJ

    Shade Tree NJ Senior Member
    Messages: 202

    No codes according to guy autozone, however he seemed "annoyed" had to come out in cold even with no check engine light on.

    Good to know about the GPR....even though works may swap for bigger one.

    Going to ford in morning for new CPS and fuel filter. Last few times I changed the fuel filter it was like an orange/rust color ( newer to diesels in past few years ). Also going to check the oil in morning before even starting when nice and cold and then again after warms up for a while.

    Thanks for all the feedback and comments, much appreciated!
  14. 98Chevy2500

    98Chevy2500 Senior Member
    Messages: 158

    AZ's $300 code reader may not be able to read all codes, especially "soft codes" as well as history. Find someone with a real scan tool, a SnapOff unit or Ford Software.
  15. Shade Tree NJ

    Shade Tree NJ Senior Member
    Messages: 202

    Only person I know with "ford software" is the dealer who charges $150 diagnostic fee to take my keys and sign on the line....have to sit and think who I know that may have a "real" scan tool. As mentioned earlier, AZ guy was bothered to come out in cold after told him check engine light was not on.
  16. plowguy43

    plowguy43 PlowSite Fanatic
    Messages: 5,281

    Going to Ford to replace a CPS is also a waste of money. You can buy one and fix it yourself for a heck of a lot less money. Part of the beauty of the 7.3 is that it's a fairly simple diesel to work on.
  17. tjctransport

    tjctransport PlowSite.com Addict
    Messages: 1,390

    where in monmouth county are you? i am just north of Matawan in Laurence Harbor, and have auto enginuity if you want to plug it in.
  18. Shade Tree NJ

    Shade Tree NJ Senior Member
    Messages: 202

    My shop is in englishtown...may take you up on plugging it in.

    Not going to have ford replace it, seems easy enough to do from what I saw online so picked up to do tomorrow if get some free time.

    Here's a pic of the fuel filter swapped out and the inside of the fuel bowl

  19. Shade Tree NJ

    Shade Tree NJ Senior Member
    Messages: 202

    Nothing in bottom of bowl, wiped down with a clean rag just dirty looking.

  20. dieselss

    dieselss PlowSite Fanatic
    Messages: 11,395

    Steel tank(s) or plastic?
    That is horrible looking. And that "stuff" got past that filter fyi.