2.4 liter engine stalling and misfiring

Discussion in 'KJ General Discussion' started by Kestis, Dec 1, 2019.

  1. Kestis

    Kestis New Member

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    My 2002 Liberty 2.4 with 230 000 miles on it is having engine issues.

    Cold starts are rough. First few seconds it barely runs and sometimes I even have to press little on the accelerator to keep it running. After a few seconds it starts running perfectly fine.

    The main issue is loss of power below 2000 RPM. It runs fine only if accelerator is depressed just a little bit. Maybe after 1/4th it starts stalling and misfiring. Load has no effect and this happens even if the transmission is on neutral. Engine runs fine after RPMs rise over 2000.

    This started about a year ago and happened only when the engine was cold. Since then it has been getting worse and now happens also when the engine is warm.

    The check engine light is not glowing and there are no fault codes.

    I've found threads about similar problems on the internet but they are not so useful. Many times the final fix for the problem is not told and there are dozens of possible ways to solve the problem. Only thing I have learned is that this may be ignition-related.

    I've checked the first cylinder spark plug because it is the only one easily accessible. It looked fine but gap was a bit too large. I set it correct but there was no effect. I also measured the first spark plug wire and the resistance was correct according to the service manual.

    What should I do next? Should I just check the other spark plugs?
     
  2. LibertyTC

    LibertyTC Well-Known Member Staff Member Moderator

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    Yes start with new spark plugs based on the under hood sticker specifications, and ensure they are all gapped correctly.
    The IAC intake air control controls the idle circuit,and throttle body spray cleaner should be used.
    The IAC port can get really carboned up so clean it & the pintle area on the bottom of IAC.
     
  3. Stephen

    Stephen New Member

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    Hey, excuse my ignorance, please clarify the acronym IAC?

    Having similar issues on my 04' 2.4 with 137 000km's on the clock. My issue seems to get worse after I've been running the car on the open road at 90-120km/h for an hour or more and enter an urban area, feels like it's chocking or flooding and there's no transfer of power to the drive shaft at all, also have to come off the gas pedal and it feels like it as to ignite again and is partially flooded. Have to apply petrol very slowly and it picks up again once I approach 2000RPM like above.
     
  4. LibertyTC

    LibertyTC Well-Known Member Staff Member Moderator

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    Stephen do you have an engine light on? If so scan for codes. Basics 101, vehicle need 3 things to run: Fuel, Air & spark.
    Start also with new spark plugs "as per the jeep's underhood specifications sticker" & gap them correctly.
    Fuel- A fuel pressure gauge connected to the fuel rail will tell us the psi reading, key on etc.
    Air: The IAC (intake air control) meters the intake air for a proper mixture.
    It can get dirty/carboned up, so cleaning the port and IAC pintle with throttle body spray cleaner may help.
    [​IMG]
     
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  5. Stephen

    Stephen New Member

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    Thanks for the help LibertyTC, going to be working through those items this morning, also managed to source the 2003 service manual and parts lists which I hadn't had 'til this week. Will keep you posted.
     
  6. Stephen

    Stephen New Member

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    PS: no engine light. I had an oil light on due to a steering pump issue which has been resolved, was leaking oil through the switch so replaced that it's okay now
     
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  7. turblediesel

    turblediesel memberable

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    Vaccuum leak?
     
  8. Kestis

    Kestis New Member

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    The engine has always had a very noticeable boost in performance when the RPMs rise over 2000. Something clearly changes in the engine control at that speed.
    I wonder if these are related. I don't think that engine speed would affect problems caused by bad spark plugs or vacuum leaks.
     
  9. turblediesel

    turblediesel memberable

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    Symptoms reminded me of when I forgot to hook up the vaccuum line going to the brake booster. Hardly idled and ran ok once past the big boggy spot. I'd just rebuilt the carb so that was my biggest suspicion.

    How's your gas mileage?
     
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  10. Kestis

    Kestis New Member

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    I found many cracked vacuum hoses so there indeed was a vacuum leak. I replaced those but the problem is still there. The engine might run a bit better but it certainly isn't okay.
    The broken hoses were part of the evaporative emission control system so maybe there are more leaks near the fuel tank. I didn't check there.

    But I wonder why the problem is worst when using wide open throttle? Then there is the least vacuum in the intake manifold and the leakage flow should be lowest.
     
    Last edited: Dec 22, 2019
  11. LibertyTC

    LibertyTC Well-Known Member Staff Member Moderator

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  12. Kestis

    Kestis New Member

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    This still has not been fixed. It seems to get better with warmer weather. Could malfunctioning temperature sensor cause this?
    Yesterday the check engine light illuminated. I checked the fault codes with the ignition switch trick and P0301 was displayed. It seems to mean cylinder #1 misfire. That certainly fits the symptoms, but the fault code is a few months late.
     
  13. Kestis

    Kestis New Member

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    I measured the vacuum today. The results were 550 mbar (16,25 in Hg) when the AC was on and 650 mbar (19,2 in Hg) with the AC off. They seem okay.
    I guess the next step would be spark plug replacement. I've tried to postpone it as the plugs are pretty hard to reach but there doesn't seem to be much more to do.
     
  14. LibertyTC

    LibertyTC Well-Known Member Staff Member Moderator

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    #1 misfire, now it shows up...
    Your 2.4 engine spark plugs according to the fsm are: RE14MCC5 Champion. Gap between 0.48 to 0.53
    Plugs should be changed every 30k.

    Coil packs, maybe time for new ones (Mopar preferably)
    Next if it is still not running properly, injector & a fuel rail psi test.

    Firing order is 1-3-4-2 for the 2.4
     
  15. Kestis

    Kestis New Member

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    It was the sparkplugs. I replaced them today and now the engine works perfectly.
    The old ones were in quite a bad shape as can be seen in the picture. Two of them had a gap of over 2 millimeters (0.080”).
    plugs.jpg
     
    Last edited: Jun 18, 2020
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  16. LibertyTC

    LibertyTC Well-Known Member Staff Member Moderator

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    Dang those gaps are shot ! How many miles or Km on those plugs any idea?
     
  17. Kestis

    Kestis New Member

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    I'm not sure. It has been serviced at a repair shop. I found some invoices from the past two years, but they did not include spark plug replacement.