1999 Dodge Truck Dodge Ram RUNS ROUGH 1999 318

Tiny
BULLRAM
  • MEMBER
  • 1999 DODGE TRUCK
  • V8
  • 2WD
  • AUTOMATIC
  • 355,000 MILES
Hello, great site, here is my problem, 99 dodge ram 318, lots of mild but idles great, had shorted upstream sensor code on scanner, so I looked under and found downstream o2 sensor had fallen onto the drive shaft and slowly rubbed til it made the wires bare, so, after reading the upsteram sensor was bad on the scanner, replaced it, and code went off, but if you hold the idle at about 2000 rpn it will slowly start to drop rpm, till it starts poping, then you have to let off, does this while you drive and taking off also, fuel pump was changed 1 year ago, upstream o2 was showing back and forth readings but said centered then rich, , downstream took along time to read, the upstream exhaust reading on the scanner said RICH all the time, any ideas, could it ba a bad downstream, since it was the one that originally got scraped, how about the coil?
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Wednesday, August 6th, 2008 AT 11:50 AM

6 Replies

Tiny
MERLIN2021
  • EXPERT
From the symtoms, it sounds like a bad converter, check the eshaust backpressure, or check manifold vacuum, with a gauge attached, hold idle at 2000 RPM, if vacuum rwading starts to drop you have too much backpressure, a sign of a bad converter(melted) Or crushed pipes.
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Wednesday, August 6th, 2008 AT 12:37 PM
Tiny
BULLRAM
  • MEMBER
Converter was replaced just a short while ago, and alluminum plate installed, under intake, no leaks yet.
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Wednesday, August 6th, 2008 AT 12:47 PM
Tiny
MERLIN2021
  • EXPERT
When the converter was replaced, was the "bed" inside broken up?If so some of the pieces may be lodged in the pipes, or muffler causing the backpressure, do the test!
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Wednesday, August 6th, 2008 AT 1:02 PM
Tiny
BULLRAM
  • MEMBER
Will, do. Thanks
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Wednesday, August 6th, 2008 AT 1:42 PM
Tiny
BULLRAM
  • MEMBER
OK. Checked converter, and vacuum stayed up untill engine just about dies, seemed ok, I changed the 2 o2 sensors because of the code and the code has stayed off for 50 miles so far, , after you drive on the highway, and come to rest, if you idle for a while, it slowly starts to lower in rpm, not quick or fast, just real slow, till you hear the IAC start screaming for air, if you tap the throttle it stops for a few seconds, I noticed if you hold the throttle open to about 1500 or a little more it will start surging, almost like a race car sound with a cam, it has a dieseling odor at that time, but just past that on the throttle it smooths out, it almost sounds like a tps, but I have no code for that, I checked it with the scan tool and it showed to be good, what about timing chain, it has never been replaced, , would the timing of the cam to the crank, be off so much this could be happening?I know it needs one just looking for any other thoughts, also the fuel pump is perfect 49--50 all the way till it dies, I watched the counts on the IAC and they drop when the engine is dying, do you think the IAC cant hold the idle. Thank you for all your help
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Thursday, August 7th, 2008 AT 5:21 AM
Tiny
MERLIN2021
  • EXPERT
If the engine has bacfired, it could have done some damage to the IAC, but try unplugging the egr and see what happens, a code may set!
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Thursday, August 7th, 2008 AT 2:42 PM

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