Need Durango Help!!

[challenger72rt]

I have an '02 Durango SXT 4.7 Litre w' 133K klicks.  A few weeks ago the A/C compressor seized, so I had to replace the unit.  The car would never warm up past the 'cold' indicator on the temp guage, and I replaced the thermostat so it heats up perfectly now. 

The problems are these -

Since the repairs, at 4,000 RPM, the car 'chugs' violently like it's misfiring or starved for fuel...but ONLY at 4K (??)

since before the repairs, and still now, I get 5 KM per litre.  It's supposed to be, what? double this??

I came to the conclusion that maybe because I was running very rich to compensate for the cold temps that the plugs are messed, and intend on changing them, but would plugs only misfire at high RPM's? 

any other thoughts or ideas?

[Moparal]

Plugs and wires mis fire the most on the upper rpms. So dont rule that out. Bad coil, water in the gas, cracked dist cap. What about a fuel filter?

[MEK-Dangerfield]

My buddy has a 2000 Dakota.  I'm not sure if it's 4000RPM, or 4500, but it will do the same thing. They put some kind of rev-limiter on there at the factory. 

[Jacksboys]

My 2000 Dakota 4.7 5-speed runs great up to 5000rpm (peak hp at 4800rpm) then you can feel the power start to drop off.  I am not sure why yours would do that at 4000.  May be the computer still thinks it is under open loop and is trying to dump in a bunch of fuel.  I know mine is rich at high rpm because someone behind you can see black smoke coming out the tail pipe.  From my understanding, Dodge programmed the computers to run this way so that there would be no chance of a lean mixture and hurt the engine.

Maybe you should replace the O2 sensors.  If they go bad, then the computer would run the engine on the rich side.

For what it is worth, I know the Durangos do not get very good mileage...in the 12-15 mpg range. 

Also the 4.7 has 8 coils, one on each plug, so you do not have a distributor or plug wires to worry about.

Good luck on finding the problem   

[Travis72]

Check for any codes in the computer, because there are a lot of codes that don't trip the Check Engine Light.    In a 2002, the on-off-on-off-on key check should work and any codes will be displayed where the odometer is.

Travis
72 Cuda

[tactransman]

Check for any codes in the computer, because there are a lot of codes that don't trip the Check Engine Light. 

  If it jerking that bad,it should be setting a code.

[ntstlgl1970]

  If it jerking that bad,it should be setting a code.

w both of these responses.

Definitely see if you can get codes out of it.
Will it do it with the A/C off at that RPM? - the A/C clutch energizing and disengaging can give the impression of an engine miss
Does it make any difference if the engine is dead cold or not when it happens (i.e. first thing in the morning)
If the jerking isn't caused by an ignition misfire it may not set a code.

About the only thing you could do on this without a scan tool is change the spark plugs, air filter and if you are adventurous, the fuel filter (filter and pressure regulator unit is inside the fuel tank).

Lettuce know what you find out, worst case you'll have to take it in...

[challenger72rt]

thanks for all of the advice guys!  I'll try a few things and see what happens