Rough idle especially after towing

ok, I've read every article & post on here and several other forums about rough idle but still am at a loss. First the truck, 2003 with 98,000 miles, auto, Quad XZT, in tank lift pump, no other power mods.



It will randomly idle very rough from a cold start (not temp cold, just first thing in the morning or after sitting all day). The rpms will drop to 500 and then surge to 1000 like it's trying to clear it's throat. Sometimes it will die when you let off the accelerator while coasting. Usually when it starts acting this way I can change the fuel filter and it will clear it up. But I've started noticing that it is MUCH worse after I tow my 5er. No problems with power when not at idle. When I pull off the interstate the rough idle starts almost immediately. This past weekend after towing just 50 miles it ran rough all weekend while driving around town in traffic, stalled several time and just was a pain in the rear.



I've tried unhooking the XZT, changed the fuel filter the day before we left, checked the wires for rubbing, all the things I've read through all the posts I can find. I buy my fuel from a very trusted source that also sells to all the local commercial trucks.



It had the new lift pump put in at 80,000 miles and 3 new injectors. The only thing left I can think of is a sticking FCA? Please, any ideas????

 

VolCTD: It will randomly idle very rough from a cold start (not temp cold, just first thing in the morning or after sitting all day).



This describes what I experienced as a bad injector solenoid...



VolCTD: The rpms will drop to 500 and then surge to 1000 like it's trying to clear it's throat. Sometimes it will die when you let off the accelerator while coasting. Usually when it starts acting this way I can change the fuel filter and it will clear it up. But I've started noticing that it is MUCH worse after I tow my 5er. No problems with power when not at idle. When I pull off the interstate the rough idle starts almost immediately. This past weekend after towing just 50 miles it ran rough all weekend while driving around town in traffic, stalled several time and just was a pain in the rear.



This sounds like a failing Fuel Control Actuator (FCA)...



VolCTD: It had the new lift pump put in at 80,000 miles and 3 new injectors. The only thing left I can think of is a sticking FCA? Please, any ideas????



Sounds like an FCA would be a good starting point... they are around $100 from Cummins... takes about 10 minutes to change, just make sure you have the correct size torx bit as the screws can strip easily.



When you say "rough idle", do you mean it acts like its missing or that the idle cycles up and down? Rough idle can be one thing, cycling idle can be another...

 

some guys have just dumped in some two-stroke oil in the fuel tank . If it runs smooth then it's the FCA

 

yeah, maybe surging would better describe it than rough idle. I sat in Pigeon Forge traffic all weekend with one foot on the go peddle and the other on the brake to keep it at 1000 RPM so it wouldn't surge or die on me in traffic.

I've been running Power Service white in it all winter and last Friday before the trip I added 20oz. of 2-stroke oil to see it would help. It's acting better during the week but it still does it every morning and afternoon after work.

Would a diesel shop be able to test the FCA or is this something you just have to try and see? I have a local shop not 2 miles from house that I would trust, at least more than the dealers.

 

Rod Run baby!!!



You're better off to just pop for the FCA. I paid 93 for mine from cummins. I had pretty well diagnosed mine and them someone told me about the 2 cycle thing. I ran an 8 oz bottle to a tank of fuel for 3 tank loads and it smoothed mine out, so I put on an FCA.



It cured the symptoms you described.

 

Yeah that was some Rod Run The parkway was packed from end to end but man where there some nice rides there, and most of them for sale if you had a LARGE wad of cash. I guess it's just time to drop the $100 bucks and replace it. Still a lot better than injectors or other things that could be wrong I guess.

 

Yeah, we started going to wear's valley and over to the Pigeon forge city limit. Still sit in traffic but you are right in the middle of it all by then.



We also hit shades of the past since it's not such a cluster F.



I have the valve does what you want. IT remidied mine and with the exception of the lwb we have the same vehicle.

 

Rough idle especially after towin - UPDATE

Well the FCA seems to have fixed my problem. I installed it last night and the truck is running as smooth as silk now. Will still need to test while towing sometime soon but I believe it's fixed this time. Thanks for all the help from you guys for pointing me in the right direction. Now lets start saving for the next mod... :-laf

 

LOL right after this thread, my APPS laid down. Truck tries to go to idle at 70mph