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960 running rough, code P-0304 900

posted by  Mr. Weekend on  Thu Jan 4 20:19 CST 2018
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Okay, the weather turned cold and my 960 started running rough. The code is misfire on #4 cylinder. So I replaced the spark plugs, which were in abysmal shape, with NGK platinums, no difference. The coils all check good, but I did try a new coil, on all the cylinders in turn, it ran worse. That's when I noticed the coil wiring harness pigtails were badly deteriorated, and the female connectors were not making it to the coil studs. Couldn't find any pigtails locally or online, so I clipped #4 & #5 off, and modified some female bullet connectors to fit.It went back to the original rough running. Do any of you know of a source for replacement pigtail connectors? The weather has been awful, so I didn't work on it today, but I'm thinking it may be a clogged injector, as the old plugs showed no sign of being loaded up with unburned fuel. Your thoughts will be greatly appreciated!








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    960 running rough, code P-0304 900

    posted by  Adirondack Blues on  Sat Jan 6 09:25 CST 2018
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    last visit: Mon Sep 8 12:11 CST 2014
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    Agree with the recommendation to check the ICM. I keep at least one spare in my parts collection for this reason.








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      960 running rough, code P-0304 900

      posted by  jimo on  Sat Jan 6 17:59 CST 2018
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      last visit: Thu May 8 10:43 CST 2014
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      www.pelicanparts.com
      Ignition control unit-good price. I bought these and put them on my car several years ago-no problems.

      Jimo








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        960 running rough, code P-0304 900

        posted by  Mr. Weekend on  Tue Jan 16 17:27 CST 2018
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        Hi Guys! Got my replacement Huco ignition module today, will change it in the am. Is the white grease that comes with it for the connector or the metal baseplate, or both? Sure do wish my hands weren't so damn big, that's a tight spot with lots of fragile hoses.








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          960 running rough, code P-0304 900

          posted by  spook on  Tue Jan 16 21:39 CST 2018
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          last visit: Fri Oct 24 08:06 CST 2014
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          Dear Mr. Weekend,

          Hope you're well. The white grease helps the unit to transfer heat to the base, and so to cool the unit. Thus, the white grease goes between the unit and the base (not on the wiring harness connector).

          Hope this helps.

          Yours faithfully,

          Spook








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            960 running rough, code P-0304 900

            posted by  Mr. Weekend on  Wed Jan 17 09:54 CST 2018
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            Thanks, Spook, I thought it didn't look like a dielectric grease.








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              960 running rough, code P-0304 900

              posted by  jimo on  Wed Jan 17 11:34 CST 2018
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              last visit: Thu May 8 10:43 CST 2014
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              Put the front up on ramps. The back one can be accessed from the bottom and maybe the front one-I don't remember.

              Jimo








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                960 running rough, code P-0304 900

                posted by  Mr. Weekend on  Wed Jan 17 15:35 CST 2018
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                Jimo, you read my mind. I jacked it up and put a heavy concrete block and 4x4 under it, pulled the wheel off. Still, may a Pox come upon the engineers who came up with that arrangement! Lousy access any way you attack it. One problem, the plug retaining clip departed, and I couldn't find it, may be in the engine pan. It's cold and will be snowing tonight, so I put a piece of Zip tape on it to hold it until I can get back under there in a couple days. It's good to be running on six cylinders!!








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                  960 running rough, code P-0304 900

                  posted by  Mr. Weekend on  Wed Jan 17 15:57 CST 2018
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                  Just did a road test, it idles well but is still running rough, but better than before. I foresee a new coil harness in my future.








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                    960 running rough, code P-0304 900

                    posted by  Mr. Weekend on  Tue Jan 23 11:10 CST 2018
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                    I rebuilt the coil harnes, using standard insulated 5mm female bullet connectors carefully folded in at the split to fit the 3.5 mm studs on the coils. Also shortened the insulation on the wire side, they fit my still serviceable clip houses perfectly. They each have six inches of new wire, and are filled with silicone dielectric, and crimped very solidly. Cylinder #4 still firing very weakly, confirmed visually with tester. I replaced it's glazed spark plug, still no go. I was hoping the bad wire would be the green/red power lead, no such luck, 13.6 volts there, it's the green/yellow trigger wire. My next step will be to bypass that wire from the back of the cylinder head grommet to the coil using piercing jumper wires. If that fails I guess I'll be moving the wiring harness around to see if it's chafing somewhere, hope to avoid pulling the intake manifold. At least I'm learning about the Volvo I love to drive!!!








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                      960 running rough, code P-0304 900

                      posted by  Adirondack Blues on  Thu Jan 25 15:58 CST 2018
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                      last visit: Mon Sep 8 12:11 CST 2014
                      [RELATED]

                      Pulling the intake isn't as bad as you think, except that one bolt on the bottom of the intake bowl. That one is tough to reach








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                        960 running rough, code P-0304 900

                        posted by  Mr. Weekend on  Sat Jan 27 10:59 CST 2018
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                        No need to remove intake: I realized I did my original troubleshooting with a bad harness, which I repaired afterwards, so I purchased another coil and fresh NGK plug, and presto, it runs great! Thank you for your help, Gentlemen!!!!








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                      960 running rough, code P-0304 900

                      posted by  beast on  Wed Jan 24 17:29 CST 2018
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                      last visit: Sun Feb 24 22:02 CST 2013
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                      Just remembered something else. I think there is a ground connection way down near the drivers side engine mount that can break or need to be cleaned up. Can't seem to find the post about that one but I'm sure someone will chime in








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    960 running rough, code P-0304 900

    posted by  jimo on  Fri Jan 5 18:08 CST 2018
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    last visit: Thu May 8 10:43 CST 2014
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    Problem could be an ignition control module, Try switching the front and back one
    and see if the trouble code moves to another cylinder.
    They are located on the front and back of the intake manifold.

    Jimo








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    960 running rough, code P-0304 900

    posted by  Mr. Weekend on  Thu Jan 4 20:30 CST 2018
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    I'll be checking fuel pressure as well.








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      960 running rough, code P-0304 900

      posted by  beast on  Fri Jan 5 10:38 CST 2018
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      last visit: Sun Feb 24 22:02 CST 2013
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      Here's a couple links:

      https://www.matthewsvolvosite.com/forums/viewtopic.php?t=24011

      http://forums.turbobricks.com/showthread.php?t=264577

      http://davebarton.com/pdf/960HarnessRepair960.pdf

      https://www.volvotips.com/index.php/940-960/volvo-960-service-repair-manual/volvo-960-basic-testing/

      https://www.volvoclub.org.uk/faq/960_90Info.html#960EngineStallsandWontRestartWiringHarness

      On the last one see "960 engine stalls and won't restart wiring harness" It has been several years but I did replace the coil wiring on my 93 960 with the cheap Volvo part #'s listed. I bought some high temp teflon sleeving from a computer parts place to protect the harnesses. It worked a treat

      Damn I miss that car. Lots of electrical gremlins tho. Also check injector wiring where it runs around intake manifols. Mine rubbed thru and shorted






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