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Discussion Starter #1
Anyone ever run into one of these 3.8L engines that just seems to ping (spark knock) any time you are on the gas a little. Seems to do it no matter what the ambient temp is outside and always around 1800 to 2200 rpm in 4th or overdrive. Vehicle runs fine. Mileage has never been more than 20 per gallon since I've owned it. It also has developed an issue with inconsistent return to what should be an idle speed of about 650 rpm in gear. Sometimes when stopping at a light it will be around 525. Touch the gas a bit it will bounce back up to where it should be. Thought this might be wear in the throttle body shaft. Over the year I have tried an IASC motor, pulled the throttle body off and completely cleaned it and the intake. Never made a change to any of the two issues. The spark knock is annoying with the windows down rolling along at 35MPH. Plugs always look good. Got 190K on it now and need to do a water pump and power steering pump. Wondering if a weak cam sensor could cause this. No codes to find except an occasional evap code from the vacuum pump once in a blue moon. The reason I ask is the last few weeks it has "burped" or suddenly stumbled like it was going to stall when accelerating and it has also suddenly dropped idle speed in gear and then recovered itself in a few seconds.
 

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Lots of owners say their van makes clicking/clattering noise, but I don't recall prior reports of pinging on this forum. Have you used an OBD realtime data stream reader to check fuel trims? If you're certain it's pinging, you could check for carbon on the pistons and valves with an endoscope. 20 MPG is very common, based on many reports from owners in the past.
 

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I should have said, 'can be caused by'. Also, part throttle pinging, although not good, is not really damaging like full throttle pinging, where the loads and explosions are much more violent.
 

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Discussion Starter #5
II'm pretty certain it isn't chattering since I can "modulate" it with a little change in gas pedal pressure. I did notice today that it does occur in 3rd gear when accelerating mildly to just moderately. Get on it hard you never hear it, really light the same. Just more of an annoyance thing than anything else. I may take a peek inside the cylinders over the weekend just to see how carboned up it might be. I get a little lead-footed once in a while just to keep the carbon out. Never hurts to look. This thing does have an EGR valve on it that failed over a year ago. When I replaced it I cleaned every passage I could get to but that doesn't mean there may still not be something restricted or that the valve I installed is calibrated to the same specs as the original. I believe it was a Standard brand replacement from a regular jobber supplier not a Joe the consumer place like AutoZone.
 

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Discussion Starter #7
Worth rechecking it. I'll post the results as soon as I get a chance to take a look.
 

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If you have that characteristic "high altitude" detonation ping, try blocking off evap purge hose from purge solenoid (it could be dumping extra fumes or ever liquid gas, if it gets in there, into intake).

BTW, I take it you're not driving above 5,000 ft elevation :)

Also, check that intake resonator box under RH fender for rodent infestation and resulting debris / blockage.
 
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