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Truck pinging on acceleration

Discussion in 'Dakota, 1998-2013 Durango and Aspen' started by Peymack91, Sep 10, 2016.

  1. Peymack91

    Peymack91 Member

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    Truck is shaping up nicely, but still a few things I need to get finished.
    Like the heading says, the truck pings on acceleration. Not badly, but enough to warrant a look-see. Idles steady at 750 rpm. New plugs and wires. Getting new cap and rotor. I don't think this would have anything to do with it, unless these 3.9 motors are really sensitive to plugs and wires.
     
  2. valiant67

    valiant67 Rich Corinthian Leather
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    Use the factory recommended plugs, probably Champion copper. But the Ping is something else, running hot, EGR, timing needs set, etc.
     
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  3. Scrounge

    Scrounge Well-Known Member

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    My Dakota with the 3.9 pings a bit going uphill, but it's been running hot at freeway speeds on hot, sunny days. When I flushed the cooling system several months ago, the pinging went away. Looks like I'll have to flush again when I get the chance. If you've yet to do so, you might flush your cooling system.

    In addition to what Mark recommends, you might add a cheap can of octane booster when you next fill up, and see if that helps. Dollar Tree sells them for $1.

    You could also have a minor vacuum leak. Check the hoses thoroughly.
     
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  4. Bob Lincoln

    Bob Lincoln "CHECK FAULT CODES"
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    Especially since the idle is typically 600 RPM, not 750. A vacuum leak may make it idle a little faster.
     
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  5. ImperialCrown

    Level III Supporter

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    I would review a list of 'possible causes' for engine ping and eliminate them one-by-one. You probably don't hear ping in the first couple of miles, only when the engine warms.
    Common causes are: high cylinder head temperatures (cooling system defect?),
    high cylinder compression pressures (carbon build up?),
    early spark timing (advanced?),
    lean mixtures (vacuum leak, O2 sensor defect?),
    insufficient EGR (plumbing carbon restriction, insufficient vacuum to valve diaphragm or leaking diaphragm or defective transducer?),
    an exhaust restriction keeping cylinder pressures high, etc.
     
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  6. ka9yhd

    ka9yhd Active Member

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    If you hear a loud hissing sound coming from the exhaust pipe, I would look for restrictions in the exhaust system.
     
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  7. Meester Beeg

    Meester Beeg Active Member

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    You didn't mention what year your Dak is. If a 92 and up it's likely a bad intake plenum gasket. These blow out and cause oil to be sucked into 1 or more cylinders causing detonation. Look intob the throttle body with a light. If the intakebfloor is wet you have work to do.
     
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  8. valiant67

    valiant67 Rich Corinthian Leather
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    From another thread,it was identified as a 1991 - the old TBI engine with a conventional distributor and throttle body.
    Timing should be checked, the plenum gasket won't be an issue.
     
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  9. ImperialCrown

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  10. Scrounge

    Scrounge Well-Known Member

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    You might check the hose between the air cleaner housing and the crankcase breather. Here's a thread on the topic:

    Have I found the vacuum leak?
     
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  11. Peymack91

    Peymack91 Member

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    To clarify, this "pinging" doesn't sound the same as if the engine was starved of fuel or running hot. This sounds more like when an engine idles really low and then you accelerate rapidly.
    Idle is at 650-700, I've gone through all vacuum hoses. If anything, it runs really cool. The gauge (if accurate) never goes over 1/4 from C. Oil pressure is great.
    Will a bad o2 sensor throw up a "check engine" light on these trucks?

    I will look into everything you guys have suggested, though. Thanks for the insight!
     
  12. Scrounge

    Scrounge Well-Known Member

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    If it happens when the engine is cold, my guess is that it's a timing problem.

    The EGR on mine is at the back of the passenger side valve cover. I recall having to reroute a line on it, as one of the outlets was plugged. I had to look at another one in the junkyard to see how it was supposed to be connected.

    Have you examined the coolant? Running that cool seems to indicate that circulation isn't complete. If the coolant is clean and the reservoir bottom is clear, maybe you should leave it alone. But if not, I'd recommend flushing. In another thread, Bob recommended removing the block plugs, as crud can sometimes accumulate there and cause blockage. The passenger side block plug on mine can be reached easily enough, but I've yet to try the driver's side, as too much else has to be removed first. I also had to replace the thermostat and its rusted housing shortly after buying the truck. You've not reported a code 17, so perhaps your thermostat is operating properly.
     
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  13. ka9yhd

    ka9yhd Active Member

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    How many miles are on this vehicle? I am thinking carbon build up in the cylinder causing the compression ratio to be higher. Might have to back off on the timing.
    A friend had an 87 Omni with the 2.2 Liter. When he had to replace the head gasket, he also cleaned all the carbon from the head. Engine ran fine without any pinging. Now I am forgetting how many miles he put on the car until the pinging returned.
     
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  14. Peymack91

    Peymack91 Member

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    Mileage is at 207,xxx
    Coolant is clear with no sludge on the cap or at the bottom of the reservoir. I'm thinking a new thermostat may be in order as it seems that it will sometimes show 1/2 on the gauge, but most often at the bottom 1/3. I would think that the gauge or sending unit would fail all-off or all-on.
    I have not checked the timing, but that will likely be my next step.
     
  15. Scrounge

    Scrounge Well-Known Member

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    Does it more often run 1/2 gauge during hot sunny days at high speeds? Or has no pattern been established? I doubt that your gauge or sender has a problem. We've not asked about leaks, though you'd probably have reported if it has any. You might check for sludge in your heater core by connecting 2 ends of a cut garden hose to the inlet and outlet on your firewall, point the outlet hose to a drain pan, then pour some distilled water into the inlet.

    You might also check the fan clutch. When you spin the fan by hand, it should only move less than a full turn.

    Is the front of the radiator blocked by dirt or bugs? If so, you might hose that off. On another thread, Rick Anderson recommended hosing from the fan side first.

    Agreed about checking the timing. Someone else might report whether a good cleaner for carbon build-up is on the market, or if that will have to done with the heads removed. Techroline cleaned my injectors good, but I don't know what else it cleans. If the carbon raises the compression ratio, a can of octane booster should help.
     
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  16. Peymack91

    Peymack91 Member

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    No pattern that I can determine. Fan clutch is good. Radiator is clean. I'm thinking a defective thermostat. It wouldn't be the first time a thermostat was an issue for me. My '95 Nissan Hardbody ran cool for months until I changed out the thermostat. Ran like a champ after that.
    Is an 85C the correct for the 3.9?
    Timing, I think, is an issue as well. Doing both should wake this truck up.
     
  17. Meester Beeg

    Meester Beeg Active Member

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    No. 89C or 192F is the correct one. Has the timing chain ever been replaced and a tensioner added? If not there is the problem. No sense setting timing if the chain is sloppy throwing everything out of time.
     
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  18. ImperialCrown

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    That would be TSB # 09-07-97 for the addition of a timing chain tensioner. The V6 was the worst offender for timing drive wear and noise issues. The V8s, not as bad.
    TSB here:
    TSB 09-07-97
     
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  19. Meester Beeg

    Meester Beeg Active Member

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    The 6 was hard on chains due to the offset of the crank pins.
    I had a 92 with 160k on it and it was noisy and made a funny noise at very light throttle settings. I sold it and got a low mile 92 V8.
     
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  20. Peymack91

    Peymack91 Member

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    OK, the pinging is gone. No idea why, just vanished a couple of days ago. Still left with this lumpy idle. Haven't changed out the thermostat, tomorrow maybe. I know running cold will give weird side effects.
    Quick question: Does the Idle Air Control Motor function only from start until engine warms or is it an "always on and working
     

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