loping at idle

[Mhannink]

so i have a buddy with an 03 auto 4x4 with 200+k miles. lately its been starting to lope at idle seems to relate to the ac kicking on and off. funny part is it almost sounds like it lopes when the ac kicks on smooths out after a bit and then lopes again when it kicks off. i havent yet really gone into looking at it but i know its a problem. to me when it lopes it sounds like and injector is missing and then goes away. the truck is all stock even the exhaust never had a chip heck its even got the original trans not a rebuild. truck is very well maintained (i trained him) runs good high dollar oil in everything and a good fuel additive.



ive been doing a little research here and cant seem to pin down what the cause might be. looking around the fca seems to be most likely but it could be fuel pump, injectors, fca, or i think i even saw something about electrical. so does anyone have an ideas

 

[SWithrow]

Does the AC blow cold? Might need recharged.

 

[seafish]

You can check the FCA by putting a few ounces of 2-stroke oil in the tank...

If the idle smooths out for awhile (doesn't lope) then it is the FCA.

That would be the easiest and cheapest test to start with.

Also TW Diesel (a diesel mechanic and member here) is very open to recieving phone calls or emails regarding diagnosing fuel system problems on our trucks !!

 

[AWeaver]

This is a weird coincidence... I was poking around today for the same reason. I have been idiling my truck a lot the past few days running the ac the whole time. Today when I started it up for the first time... no ac at all. When I turned it off and back on, it had a loping idle for a few seconds that seemed to coincide with the compressor trying to kick on. I drove it around a little and shut it off and ate lunch. Came back fired it up and all the sudden cold ac and idiling fine. WTH? Ive posted threads about mine having a rough idle before as well and have had the same responses... fca, injectors, electrical, etc. Just thought id chime in here since we seem to have some of the same issues.

 

[Mhannink]

swithrow ac blows ice cold and i hear the compressor cycling normaly when im outside the truck. ill hear the click then a second or 2 after i hear the lope like its missing on a cylinder but not a total miss. after a time it clears up idles fine and then i hear it again using preceded by the ac clicking on. seafish thanks for the info ill try the 2 stroke oil and see what it does. though i believe my buddy does run schafferes diesel treat in every tank.

 

[TCDiesel]

When temps Above 85* the A/C should not cycle more then 1 time in 4 Minutes or longer.

 

[Mhannink]

i havent checked cycle times. im positive its a fuel related problem brought on by the increase load the compressor puts on the engine. im just not sure exactly what is causing the problem. fca injectors fuel pump... ...

 

[TCDiesel]

loping at idle 80% of time FCA , the other 20% COV,Lift,Gear pump. I doubt your problem is related to Injectors W/O other symptom's.

 

[steved]

A "miss" is attributed a lot of times to a weak injector solenoid. I fought this for a while... it will likely get worse when the weather gets cold.