2003 Dodge Ram Poor Power and MPG

DODGE RAM
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TRUCKS123
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I have a 2003 ram 2500 5.7 Hemi that is well maintained it has 126000 miles on it .I just last month had the spark plugs ,wires PCV replaced fuel system cleaned with motorvac and syn oil change. it ran great for about a week after than then had a marked drop in power and torque over the entire power band .my milage is terrible according to the overhead display and gets worse when hitting hills and inclines as low as 4-5 miles to gallon and even worse when cold . but when on a flat road with no wind its normal Its not showing any codes not when checked with a scanner are any present . it idles pretty much normal although sometimes when coming to a stop its a little on the high side. The engine doesn't sound like it did before this happened and is not quick to rev as it was before and is slow coming down from rpm and the exhaust tone is not the same much more in cab drone . Some one said it could be a bad cat or weak fuel pump. Can you help thanks in advance
Feb 10, 2007 at 5:14 AM
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CARUNDELL
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Hey trucks,
Was the truck scanned with just a code reader? Or scanner that can show datastream values? One possibility would be faulty/failed O2 sensors and a datastream "view" would pretty much diagnose it. I would recommend further testing (if possible) Let us know!

Chris
Feb 10, 2007 at 8:57 PM
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TRUCKS123
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Thanks carundell. So my superchips scanner/programmer won't detect a bad o2 sensor or is that the sensors could be out of range . In that case im heading to the dealer right away and have them check it out .I thought it was something I could resolve but it looks like your right in having it checked out with a proper diagnostic tool. This is the first performance problem i have ever had with this truck and i thought it may have been easy to fix. Hopefully its as easy as putting a new sensor or sensor's in much cheaper than a fuel pump or new cat
thank you ..
Feb 10, 2007 at 10:50 PM
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SKETCHBAL1
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On my ram hemi I have problems with the accuracy of the guage that tells you the mpg. It is very inconsistant and always wrong. If you haven't found a problem with your engine, you might try doing a manual check of the mpg's to make sure the gauge isn't faulty.
Feb 11, 2007 at 4:41 PM
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TRUCKS123
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k so took the beast into the Dodge dealer last week they hooked it up to there scanner found no codes did find the downflow 02 sensor out of range and thermostat reading only 172 degrees .Said could have blocked cat and sensor reacting to it. So off i went to my garage tok the cat off and yes it was partilly blocked
installed a new aftermarket one also intalled a new 02 sensor and a new thermostat
the truck runs better now, gets better milage but still not like it was 2 months ago .I even checked all the recenty installed plugs and they looked good
I may intall the other 02 sensor on the upside of the cat to see if that makes any difference
and maybe a new IAT sensor ???
Feb 23, 2007 at 11:22 AM
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CARUNDELL
  • ✓Experienced Mechanic
  • 602 POSTS
[quote:cdebca4c40="trucks123"]k so took the beast into the Dodge dealer last week they hooked it up to there scanner found no codes did find the downflow 02 sensor out of range and thermostat reading only 172 degrees .Said could have blocked cat and sensor reacting to it. So off i went to my garage tok the cat off and yes it was partilly blocked
installed a new aftermarket one also intalled a new 02 sensor and a new thermostat
the truck runs better now, gets better milage but still not like it was 2 months ago .I even checked all the recenty installed plugs and they looked good
I may intall the other 02 sensor on the upside of the cat to see if that makes any difference
and maybe a new IAT sensor ???[/quote:cdebca4c40]

Trucks,
Wouldn't worry too much about the IAT(unless it codes), but a new upstream O2(s) may be a good PM move (due to excessive carbon contamination) also recommend reseting the fuel adaptives as the PCM may have "learned" some funky settings due to the clogged cat

Chris
Feb 23, 2007 at 8:37 PM

Suggested Repair

After replacing the partially blocked catalytic converter, downstream oxygen sensor, and thermostat, install new upstream oxygen sensors because of possible carbon contamination and reset the fuel adaptives so the PCM can relearn. Do not replace the IAT sensor unless it sets a code.

Conversation Summary

A 2003 Dodge Ram 2500 5.7 Hemi lost power and fuel economy across the power band with no stored codes after recent plug, wire, PCV, fuel-system, and oil service. An expert suggested checking live data for faulty oxygen sensors. The dealer found the downstream oxygen sensor out of range and the thermostat reading only 172 degrees, and suspected a restricted catalytic converter. The owner confirmed a partially blocked converter and replaced it along with the downstream oxygen sensor and thermostat; performance and mileage improved but did not fully return. The expert advised against replacing the IAT sensor unless it codes, recommended new upstream oxygen sensors as preventive maintenance, and suggested resetting fuel adaptives.

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