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3.5L Miss When Cold

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  • 3.5L Miss When Cold

    So I'm looking for some help, I have a NH pajero that's been converted to a 3.5L with aftermarket computer and tune. Recently it's developed a miss. The miss is only there until it reaches operating temperature and between 1000 - 2000 rpm and clears up after that. If I spray aero start down the intake the miss will go away, so I am guessing its a fuel related issue. I have changed the coolant temp sensor thinking it might be that but no change. Any help would be great as it is doing my head in. Thanks in advance

  • #2
    Identify which cylinder may have water leaking into cyl. Pull plug and have a look you may see evidence of water ingress into cyl. Common problem and once it clears itself runs ok.

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    • #3
      Thought the same so did a co2 check and was all good, it's not using water either. Could it still be a head issue? Forgot to mention in earlier post engine was rebuilt approx 50,000kms ago, it is also very hard to start and is getting worse
      Last edited by Pajo26; 07-12-13, 05:29 PM. Reason: .

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      • #4
        Could it be something as simple as plugs/leads? When were they changed last? A more expensive options could also be the coil packs.
        Cheers, Bundy.

        Currently: 2001 NM GLS MY2002 3.5 V6 Manual, Bullbar, GME TX3520, Falken Wildpeak A/T02 LT265/70/16, Pacemaker extractors, KYB Skorched 4's, Villain Lighting 22" lightbar, Bushskinz Front and sump guard, Pioneer 7" screen

        Items to be fitted: ARB 2.5 x 2.1 awning.

        Items to be purchased: Bushskinz- Gearbox/Transfer plates and sliders, Roof racks, Safari Snorkel, Lifted Springs, maybe more...

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        • #5
          Plugs and leads haven't been done since I have owned the car but this miss goes away which is what has me leaning away from that

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          • #6
            0. Check fault codes.

            1. Find the cylinder that has the problem

            2. Visually check spark plug from that cylinder (hope its on the easy side). The problem is usually indicated on the plug itself either by fouling, rusting, or burning of the plug.
            (Blocked or leaking injector can be found here i.e. very wet or very dry plug)

            3. Check spark quality and consistency to that cylinder.
            (coil or lead problem found here)

            4. Check injector pulse to that cylinder.
            (ecu, or wiring problem etc. found here)

            5. Check compression on that cylinder.
            (Head gasket. Piston ring or piston or valve/cam problems found here)

            Cant isolate the problem cylinder ? Check fuel pressure. From symptoms you are describing i suspect fuel pump issue.
            Air flow meter is also a possibility.

            If you do everything i have said and still cant find the problem you need someone good to spend some time on it.
            NJ Pajero 3500 DOHC AUTO

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            • #7
              Thanks for the advice will start checking this weekend

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              • #8
                First thing I woukd be doing is a error code check then a compression test (might as well do plugs while you're there, leads are always a good idea if age is unkown also).
                Could be leaky valve/s, lead or plug on it's way out and being quenched from rich mixture when cold etc.
                97' NK 3ltr GLX LWB Manual | 3" lift | Wildcat headers | K&N air filter | 2.8 crawl gears | 4Terrain clutch | 2.25" exhaust | Factory locker rear | TJM 10,000lb winch | TJM snorkel
                97' NL GLS LWB Auto | 6G75 3.8ltr | Redback Headers

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                • #9
                  So it turns out the problem was a bad fuel pump as Kubrick suspected. I checked the fuel pressure and it was 32psi which I dint think was to low but when I clamped the return line the pressure didn't go up so I knew it was time to change it. Thanks for the help

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                  • #10
                    Have you got the new pump installed yet?
                    97' NK 3ltr GLX LWB Manual | 3" lift | Wildcat headers | K&N air filter | 2.8 crawl gears | 4Terrain clutch | 2.25" exhaust | Factory locker rear | TJM 10,000lb winch | TJM snorkel
                    97' NL GLS LWB Auto | 6G75 3.8ltr | Redback Headers

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                    • #11
                      Have you got the new pump installed yet?
                      97' NK 3ltr GLX LWB Manual | 3" lift | Wildcat headers | K&N air filter | 2.8 crawl gears | 4Terrain clutch | 2.25" exhaust | Factory locker rear | TJM 10,000lb winch | TJM snorkel
                      97' NL GLS LWB Auto | 6G75 3.8ltr | Redback Headers

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                      • #12
                        if it was fuel related wouldn't you expect to be running bad in the upper rev range given that the engine would be starved of fuel.
                        ive had the same issue to happen to me. the first time it was leads that had done 300thou. I tested them for resistence and they where twice that of new ones so they where well and truly stuffed. the second time was in a vehicle that had 160 thou on it. turns out no one bothered to change the plugs at 100thou. first thing in the morning when cold number 5 flatly refused to play the game until the engine was warm. needless to say plugs where so stuffed it wasn't funny one of them would have had a 3mm gap easy as apposed to the factory 1mm from memory

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                        • #13
                          I have had a similar issue with my 3L NJ. I had a shocking miss and could even see sparks on the outside of the leads. Change leads and has be great ever since. I got TopGun brand of ebay for $85 posted.
                          1994 NJ GLS Pajero 3L Auto, Tigerz11 steel rack and awning, Alloy BB, Yokohama Geolander AT/S, Narva Driving Lights, Soon to be lifted!

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                          • #14
                            Yes I have installed the new pump pauly, I agree with you bundyjr didn't think it would be fuel pressure related but new pump has fixed it

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                            • #15
                              Originally posted by Pajo26 View Post
                              Yes I have installed the new pump pauly, I agree with you bundyjr didn't think it would be fuel pressure related but new pump has fixed it

                              you said it was running at something like 36 psi.
                              any idea what factory spec is for the pump. something like 60 or 70 psi is it?

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