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Misfiring on 2 & 7

2001 Silverado. Problems started with codes results showing, misfiring on #2 & #7. Since them, I have: Replaced the intake gasket and torque. New plugs, wires, coils on 2 & 7, PVC, Fuel reg, TPS, fuel injector on 7, Fuel filter, Compression test is 180 - 155, Fuel pressure is 52, very poor fuel economy, idles @ 600 while in park. When we disconnect the connector to the TPS, and re-plug it, the idle goes to 1,100 while in park and sounds great. Later on it returns to its previous condition. Thanks for any help.

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  • Rick
    Rick Mar 22, 2014

    Rechecked the codes and there were. P0101,P0102,P0370,P0122. Erased all of them and ran the truck for a bit. The only code at the moment is P0307.

  • Rick
    Rick Mar 22, 2014

    thats P0307, not P0370

  • Rick
    Rick Mar 24, 2014

    Yes, but not ready to say I need a valve job. Vacuum tested at 25 psi. Replaced the uptream o2 sensors on both banks. This engine isn't sounding like a serious internal issue. Next up is a check of the Throttle body motor and a smoke test.

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  • 77 Answers

Hate to say it but I would look at the valves on those cylinders. I would venture they are not sealing properly.

Good luck.

Posted on Mar 20, 2014

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SOURCE: 95 GMC Jimmy 4.3l W vin rough idle

My problem was solved when I repaired my 4 wd activation dash switch. The switch was contacting on 2WD & 4HI at the same time. The front differential activation is vacuum activated possibly creating a tug of war that didn't actually engage it but drained off vacuum from the engine? A theory at best but stumbbled across it because I knew the switch wasn't working properly I repaired it and low and behold rough idle disappeared and all is good for 3 weeks running.

Posted on Dec 10, 2008

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SOURCE: Have a 2003 Taurus, 3.0 engine that has a misfire

Sound like an air / vacuum leak to me.
Re-check for an air leak on #2 cylinder inlet manifold.
Use a propane torch (unlit, of course) to flood propane gas around inlet manifold/head flange & gasket area.
If there is any change in idle speed during this test you have a vacuum leak.

Posted on Aug 18, 2009

SOURCE: Have a 1999 Toyota Tacoma with a 3.4. Vehiclw was

Most likely I a would suspect the fuel rail had moisture in it. If you checked emissions it would most likely show no HC and alot of 02 and no CO. If it does show alot of HC then I would suspect sticking valves intermittantly . The pinging really points to no fuel issue tho. If you pull the injector connector off and no change then I would remove the fuel rail and inspect. Also make sure the wires are in the correct locations. It easy to get them wrong.

Posted on Sep 03, 2009

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SOURCE: 2003 kia # 3 misfire/ runs rough

Replace the coil for number 3 cylinder.

Posted on Nov 11, 2009

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Before blaming a head gasket, test the Injector wiring and follow the wiring to the connector for a corrosion check on the pins. If no success do a compression check on #2 and # 3 as they are adjacent to verify a blown headgasket.

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