1. This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn More.

1988 F250 7.3 IDI misfire starting at 2,500 rpm

Discussion in '6.9L IH & 7.3L IDI Diesels' started by jdbaugh1, Apr 2, 2020.

  1. jdbaugh1

    jdbaugh1 Registered User

    Posts:
    4
    Likes Received:
    0
    Joined:
    Apr 2, 2020
    Location:
    Kansas
    I've been searching the internet for people that experienced similar symptoms to what I am seeing and have found a couple that appear to never have been solved. Essentially the truck starts fine and it runs really will up until around 2,500 rpms. The truck only has 130K miles on it and the oil has been changed ahead of schedule most of the time. If I rev the engine up in neutral it will start misfiring about right at 2,500 rpm on what seems like a single cylinder. It will continue to rev up with more throttle but the misfire is persistent from 2,500 on up to redline. The smoke at misfire is whitish blue.

    This truck has been parked for extended periods of time. Before I acquired it they probably used it a could to maybe 4 times a year. If anyone has any guesses your input would be greatly appreciated. 0327201915d-02 (1).jpeg
     
  2. hesutton

    hesutton The Anti-Anderson Supporting Member

    Age:
    44
    Posts:
    8,145
    Likes Received:
    689
    Joined:
    Aug 19, 2005
    Location:
    Bowling Green, KY
    How many miles on the injectors and injection pump?
    Used oil analysis?
    Miss only when rev'ing in neutral?
    Oil consumption between changes?
    What trans?
    Video of this happening?

    Heath
     
    Scotty4 likes this.
  3. DaveBen

    DaveBen Supporting Member Supporting Member

    Age:
    71
    Posts:
    1,584
    Likes Received:
    365
    Joined:
    Sep 29, 2010
    Location:
    Ukiah, Ca
    He just acquired the truck, so no history.
     
  4. jdbaugh1

    jdbaugh1 Registered User

    Posts:
    4
    Likes Received:
    0
    Joined:
    Apr 2, 2020
    Location:
    Kansas
    No oil analysis yet.

    Miss is in neutral and I'm not sure if the mis is there under load. It seems to die off up top more than I'd expect it but I don't really have a baseline. This is the only IDI I've driven. I assume it could be missing under load as well.

    Haven't had it long enough to monitor oil consumption. What is excessive?

    5-speed transmission. The ZF-S4 I think is designation from memory.

    I can get a video of it happening. Basically it can hold revs very smooth until 2,500 and at that point it starts smoking and shaking a bit. Like a single cylinder constant misfire. It cleans up some with higher rpms but it's still there to an extent. Right at 2,500 is where it is the worse.
     
  5. jdbaugh1

    jdbaugh1 Registered User

    Posts:
    4
    Likes Received:
    0
    Joined:
    Apr 2, 2020
    Location:
    Kansas
    Forgot to say injectors and injector pump are original so 130k on those
     
  6. hesutton

    hesutton The Anti-Anderson Supporting Member

    Age:
    44
    Posts:
    8,145
    Likes Received:
    689
    Joined:
    Aug 19, 2005
    Location:
    Bowling Green, KY
    Definitely time for an IP and injectors. They are way past their service life. Could be fuel related, but a video would help. Drive it and see how it acts in that RPM range.

    Heath
     
  7. aggiediesel01

    aggiediesel01 Full Access Member

    Posts:
    271
    Likes Received:
    213
    Joined:
    Dec 29, 2016
    Location:
    Houston, TX
    Lot's of little easy things to try before throwing in the towel on pump, especially if it's sat a lot. First try a new fuel filter filled with ATF, start it and let it idle until the sound noticeably changes and shut it off and leave it over night. Then drive it as normal or a little heavier than normal for the next day or two and see if it resolves. The chemicals in the ATF can help clean and lubricate sticking pumps and injectors. If that doesn't work then put a fuel pressure gauge on the filter header at the shrader valve and monitor fuel pressure as you slowly rev the engine up to 3k. I believe the pressure should be between 3 and 6 psi throughout the range. If it's low you likely have a weak fuel pump and that could be contributing to the problem. If the miss is very consistent you can hold the engine at that RPM and loosen each injector line to see if one of them doesn't change how the engine is running. This can pinpoint a specific injector that is bad. It's not uncommon for an injector to stick open at elevated RPMs. If you can isolate one that is giving trouble, then it can be rebuilt or replaced. With that many miles and not much history it would be advisable to pull the injectors and have them pressure tested/shimmed to bring them back up to spec. With a fuel system that's been cared for it's not uncommon for these pumps to last over 300k. So, if the previous owner changed the fuel filter like you say they did the oil then the fuel system might be fine if only a little lacquered up from sitting so much.
     
    jdbaugh1 likes this.
  8. Oledirtypearl86

    Oledirtypearl86 Full Access Member

    Age:
    34
    Posts:
    1,317
    Likes Received:
    670
    Joined:
    Sep 17, 2018
    Location:
    Whitehall MT
    If it was mine I'd dose it with some hotshots and run the piss out of it for half a tank but I'd bet it's an injector
     
    jdbaugh1 likes this.
  9. jdbaugh1

    jdbaugh1 Registered User

    Posts:
    4
    Likes Received:
    0
    Joined:
    Apr 2, 2020
    Location:
    Kansas

    I had someone on facebook recommend adding ATF to the fuel tank but never answered back about appropriate concentration. Would it be effective to dump some in the tank and go for extended drive or just douse it via filter fill and let it hot soak work better?
     
  10. aggiediesel01

    aggiediesel01 Full Access Member

    Posts:
    271
    Likes Received:
    213
    Joined:
    Dec 29, 2016
    Location:
    Houston, TX
    In the tank is more of a periodic maintainence thing. If you have an issue, high concentration directly applied to the injection system by putting it in the filter and running it into the pump and injectors and letting it sit is the most effective and fastest way to make a correction if it's going to work.
     
    jdbaugh1 likes this.

Share This Page