1998 Dodge Ram rough idle

1998 DODGE RAM
115,000 MILES • V8 • 2WD • AUTOMATIC
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HARDIE775
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  • 10 POSTS
When my engine is in park and idling, initially it's fine. according to the tachometer on the dash it's idling at about 7500 or so. after about 3 minutes though the idle starts stumbling and hissing from the top of the motor right under the air filter. the exhaust stinks. very rich i think and the tail pipe is spitting fluid, though it does not smell much like gas. the rpms go down to about 4500 and just shy of a stall. what does this sound like to yall.
May 28, 2008 at 5:36 AM
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MERLIN2021
  • ✓Experienced Mechanic
  • 17,250 POSTS
It sounds like I would be removing the plenum and inspecting for any fluid or air leaks....the idlle by the way is 750....7500 and the engine would explode!
May 28, 2008 at 6:50 AM
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HARDIE775
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  • 10 POSTS
i appreciate the feedback. obviously i added and extra 0 on the rpm, anyway, thanks for the input on the plenum. my reserch on this issue shows that my vehicle is subject to problems here, though the oil is not being over consumed. i did an oil change 10 weeks ago and almost no oil has been consumed and i'm not getting a spark knock/ping. their appears to be no leakage around the manifold, but how can i check for any vacuum leakage on my own?
May 28, 2008 at 9:56 AM
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MERLIN2021
  • ✓Experienced Mechanic
  • 17,250 POSTS
get a can of spray gumout, spray the vac lines and maniflod area, when the idle changes, youve found the leak! You want the engine running and spray on the outside but do direct the stream onto the hoses, if it is a vacuum leak, the engine idle will change speed, then you have detected a leak, repair the vacuum leak and see how it runs! If that doesnt do it, you may need a new idle air control valve, it's bloted to the throttlebody
May 28, 2008 at 10:14 AM
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