Intermittent Rough Idle

[JTodd]

Hey Guys,



Been reading through all of the "rough idle" posts and I am pretty sure that my issue is a failing FCA, but not all of my symptoms match up perfectly. Truck is an '06 with 99k miles... A few months back I noticed an intermittent rough idle at start up. . Idle smooth as silk for a 15-20 seconds, then rough and lopey for 5-10 seconds. . I noticed that the rough idle corresponds directly to voltage drops on the voltmeter (assuming when the grid heater is kicking in). . Voltage drops, rough idle, voltage returns, smooth idle. . After maybe 3-4 minutes of this cycling, the truck smooths out and idles just puuurfect. . Is this symptomatic of a crapped out FCA? I did have one single episode of white smoke on a cold start up after the truck had been sitting for several days, but it is not consistent. A while back it went through a phase where is would go into limp mode and throw a code (cant remember the exact one) but it was something about a fuel system short, and the research I did at the time led me to believe it was likely needing the valve cover gasket and injector harness replaced. .



Looking forward to your insight... Going to purchase a new valve cover gasket/harness and FCA (known failure item anyway) but want you guys input on if there may be other issues at work here. .



Thx

 

[ssanders60]

rough idle

For the last 3 or 4 years during cooler weather I've had rough idling, stall outs, and loping, even in warm weather until I started buying diesel fuel at

raceway or Shell instead of fuel at Walmart (Murphy oil). Went back to Walmart and it started it again, changed back to a new Raceway station and

Shell, truck runs like it did when it was new. To get by in the past I had to use an additive to correct it, but that's not necessary anymore. While fuel at Walmart is very clean, it must be lacking something like Cetane or sufficient lube.



Once I thought it might be the batteries, they are almost 9 years old, I understand

you'll get reaction from the EMC when the batteries get old. Florida weather,

rarely ever requires the heating grid to operate.





'03 4x4 quad cab 114,000 miles, all stock.

 

[JJPage]

My volt gauge does not drop with the cycling of the grids, but if it did, and that corresponded with the rough idle, I would be looking at batteries, and also excessive amp draw from the grids... (bad relay).

 

[EDankievitch]

My 05 has done something like this ever since I replaced the injectors. It will miss fire when the heater grids or the fuel heater cycles on and off. The miss will be a real quick stumble like one cylinder ether does not fire or fires out of sync. will only do it at idle and stops when the heaters stop cycling. My batts are about 6 years old but load test ok. seems like the computer is seeing a voltage spike and it causes the miss/ stumble.

 

[JTodd]

Well my batteries are less than a year old and spin the engine very well so I feel confident they are good and strong. . Swapped out the FCA last night and it sure made a difference on how quickly the truck starts up, it's near instant now where before it would take a few seconds of cranking. .

Went out this morning to start it and it wasnt cold enough for the grid heater to kick on so it idled very smoothly and didnt buck at all. .

Yesterday for the first start after changing the FCA it idled very rough and smoked white for about 30-45 seconds, but I am assuming that is a result of the air I introduced to the system when changing the FCA?

 

[JTodd]

Had a morning cool enough that the grid heater kicked in. . The rough idle was much diminished, but not gone altogether. . Could this be a failure of a component in the heater system causing extraordinary current draw, or maybe my alternator starting to give up the ghost?

 

[steved]

Hey Guys,



Been reading through all of the "rough idle" posts and I am pretty sure that my issue is a failing FCA, but not all of my symptoms match up perfectly. Truck is an '06 with 99k miles... A few months back I noticed an intermittent rough idle at start up. . Idle smooth as silk for a 15-20 seconds, then rough and lopey for 5-10 seconds. . I noticed that the rough idle corresponds directly to voltage drops on the voltmeter (assuming when the grid heater is kicking in). . Voltage drops, rough idle, voltage returns, smooth idle. . After maybe 3-4 minutes of this cycling, the truck smooths out and idles just puuurfect. . Is this symptomatic of a crapped out FCA? I did have one single episode of white smoke on a cold start up after the truck had been sitting for several days, but it is not consistent. A while back it went through a phase where is would go into limp mode and throw a code (cant remember the exact one) but it was something about a fuel system short, and the research I did at the time led me to believe it was likely needing the valve cover gasket and injector harness replaced. .



Looking forward to your insight... Going to purchase a new valve cover gasket/harness and FCA (known failure item anyway) but want you guys input on if there may be other issues at work here. .



Thx

Mine did the rough idle during the heater grid cycling... it was "fixed" when the injectors were replaced and it was suspected one of the injector solenoids was "weaker" than the others and would quite actuating at lower than normal voltage (like when the grid heaters cycle on).



Mine also acted this way when really cold, and again; it was suspected the solenoid was not working because of the increased resistance (whether mechanical or electrical) because of the cold.



The truck ran and drove fine when warm...

 

[cerberusiam]

Yesterday for the first start after changing the FCA it idled very rough and smoked white for about 30-45 seconds, but I am assuming that is a result of the air I introduced to the system when changing the FCA?

The HPCR system is self bleeding, no air gets into the rail . If it did the truck will not start.



It could have been the FCA sticking initially or likely your real problem giving a clue.

 

[JTodd]

So is there a method I can use to test my injectors myself?

 

[cerberusiam]

You can test the return flow to see if there is excessive return indicating wear.



You can have a scanner do a cylinder contribution test to see if that will show problems.



Thats about all you can d aside from pulling them and sending to a competent tester for more tests.

 

[AStewart]

Did you fix your problem?