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Thread: Random misfire (P0300 & others + sometimes no AC)

  1. #16
    Join Date
    Mar 2008
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    A simple noid test to the cop terminals is an cheap easy test. My own car had cyl 8 misfire and it ended up being a kinked wire right at the terminal and the insulation looked perfectly fine. Couldn’t see it but the noid light easily spotted it.. Them wires are tiny.


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  2. #17
    When this was first happening, after the usual suspects were check and replaced with no lasting results, my guy went through EVERYTHING and actuated it ALL. Literally the whole Snap-On menu, every function, every applicable screen. Nothing red flagged otherwise he would have addressed it. So maybe, lets say, the EGR wasn't sticking at the exact moment he was testing it. Doesn't mean it is 100% functional. He obviously caught the vehicle on a good day and all the actuating in the world would be moot.

    A smoker, noids, and lab scope. Not too expensive. Can always loan the stuff out to folks in need too. My guy did all that in the beginning, but like I said, nothing was acting up AT THAT MOMENT. I'd need to have all this equipment in the car all the time and pull over at the first sign of misfire. Pop the trunk and it's like the MiB car but instead of cool shiny alien weapons, it's wires, boxes with blinky lights, and tools.

    No harm in swapping the battery.

  3. #18
    Join Date
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    and after the battery swap?. . .
    ncmm
    '04 Silver Birch MM 300A, build date:03/11/04, bought new 10/04 traded 8/08, 27k miles,

    '04 Silver Birch MM 300A, build date:12/23/03, bought used 3/16/12, 24k miles
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  4. #19
    Join Date
    Feb 2017
    Location
    New Orleans, LA
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    Excluding any mechanical problem which I think you've ruled out
    there is only 5 possible causes for your issues and they are as follow:

    1> If RPM does not exceed 1500 rpm at cold start you could get false misfire codes
    2> If cold startup enrichment fuel is insufficient (weak pump or dirty injectors)
    3> Excessive oil in the intake manifold
    4> Wrong oil filter (use motorcraft only)
    5> Weak coil(s)

    I am basing this on my 03 marauder which had the exact same codes and did the exact same thing. Mine was usually quick to set a check engine light on cold startup though and idle like poo.

    btw, the autoenginuity scan tool was a waste of money. You could get a moates quarterhorse that has far greater diagnostic abilities. That's how I diagnosed and fixed this same problem on my car. Been over a year and hadn't had a problem yet.

  5. #20
    Alrighty sorry for the late replies fellas.

    SPRING UPDATE:

    New battery - no change. The old one was dead. I was a bad boy and didn't start it all winter, and no trickle. Oops.

    After the new battery, it ran pretty nice for around 50 to 75 miles. Tiny little shake on idle after a few min of running to warm it up, but not bad. Cleared fresh PCM jidders perhaps. All in all, pretty smooth idle and steady at around 600 rpm. Next morning, after about 45 min of driving to work (around 30 miles of a 40 mile trip) the light came on while still on the highway and at speed. P0300. No change in performance really. Cleared code in frustration en route. Started to drive home that afternoon, about 10 min and 5 miles on back roads later, same code. Cleared. Drove this morning, after a while code.

    Still must register a serious enough error because the AC compressor is shut down after first code and it's getting warm out so it really sucks.

    My next line of attack:
    -Smoke engine. Again. Recommendations on personal smoker I can afford? I want to do it myself not have my mechanic do it.
    -replace EGR (even though it's been actuated via snap-on tool previously)
    -TPS? I notice the throttle sticks just a touch and I have to goose the peddle ever so slighty when it's closed sometimes. Gonna clean throttle and grease the cable/pedal.
    -fuel filter, oil, filter (regular maintenance)
    -Did old battery die because of a weird hidden ground? And no, before someone asks again, the harness behind drivers side cover is fine. I de-loomed it, inspected, wrapped and zip tied out of the way last fall. All the grounds I can find have been disconnected, cleaned, dielectriced, rebolted.

    I'm due for MA state inspection by June 30th latest and they will fail with a light so she's gonna be grounded unless I can fix this asap. Not to mention I want my car working.

    Quote Originally Posted by decipha View Post
    1> If RPM does not exceed 1500 rpm at cold start you could get false misfire codes
    2> If cold startup enrichment fuel is insufficient (weak pump or dirty injectors)
    3> Excessive oil in the intake manifold
    4> Wrong oil filter (use motorcraft only)
    5> Weak coil(s)
    1> Engine starts normally every time. I dunno 1800 or 2k rpm rev? Whatever is normal.
    2> Injectors are new as of a few years ago when the random light started. Haven't changed pump, but why trip code after many miles? No performance issues at low or high speeds. She moves well.
    3> As I stated in my first post, the PCV grommet detent retaining bumps on the valve cover are slightly warn causing my PCV to cant slightly. It seems tight though. I will seal with RTV and wrap the snot out of it with electrical tape.
    4>Filter is Motorcraft
    5>Coils (Motorcraft), plugs (XP104), electrical connectors (generic but soldered and heat shrunk), and Granatelli connectors are NEW. See post 1.

  6. #21
    Join Date
    Jun 2017
    Location
    Oxford, PA
    Posts
    459
    according to http://www.myautorepairadvice.com/p0300.html

    What Causes a P0300 Code?
    Low Fuel Pressure
    Vacuum Leak
    EGR system malfunction
    Internal Engine Problems (such as low compression)
    Less Common Causes
    Faulty Coil
    Faulty Spark Plugs and/or Wires
    Camshaft or Crankshaft sensors
    Ignition module
    Computer


    Does your scan tool report fuel pressure as the car is running?

  7. #22
    Alrighty, so the latest. Thought I updated this thread weeks ago. My mistake.

    -Replaced EGR
    -New cam position sensor
    -Removed, inspected, and re-clamped some vacuum lines just because
    -Cleaned MAF
    -Oil, filter, fuel filter
    -New Crankcase Ventilation Retainer (the thing the PCV valve 'clicks' into on the valve cover. Mine wasn't clicking)
    -New crankshaft position sensor (I looked back in the records. CPS "may not" have been replaced since it wasn't on my mechanics slips. Swore it was. Did it again anyway.)
    -Disconnect battery, sit, drive
    -AC tested and recharged

    Now it's several hundred miles later. Maybe 15+ cold cranks or more

    Still getting:
    P0315 – Crankshaft position system variation not learned
    P0300 - Random Misfire

    Still not right. Sometimes engine shakes a little at idle like I have lopey cams, sometimes a specific COP showing misfiring. Never the same COP. Swapping COPS does nothing. Sometimes she drives perfectly, as in: put a glass of water on the engine and no ripples. Other times like a giant poop.

    I'm reading conflicting information on the "crank relearn" procedure. What is the drive cycle on this?

    Pretty much fed up. Guys, I'm not new to these cars. I know them. New PCM? AT this point, I almost have nothing left.

    Anyone in New England want car?

  8. #23
    Join Date
    Sep 2010
    Location
    Western WA
    Posts
    801
    From what I've read the crankshaft variation is learned during deceleration fuel cutoff when speed has been above 60mph. So you need to clear the codes and find some place where you can get it up to 60+, take your foot completely off the accelerator pedal and wait until the car slows down to 40 mph or below. Do it 3 times and it should learn that.

    Instead of spending the big bucks on the AutoEnginuity system with the enhanced Ford package consider ForScan. OBDLink is a good communication device. Personally I use the MX as it will read the Medium Speed CAN that some of my newer Fords have but a LX will do everything that can be done on a Marauder. ForScan will give you almost all of the functionality of IDS, including Mode $06 and the ability to change some settings on some vehicles. The software included with the OBDLink will also give you Mode $06 for all brand vehicles.

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