idle is erratic please help

[JFrey]

started my truck this morning is was 28 degrees. so it auotmatical go to fast idle at 1000 rpm's. then the truck starts to shake like it is missfiring. is it possible that i have a bad injector, Fueling problem, dirty injector, TPS. and when i depress the brake it comes back to the norm 750 rpm. and the shaking of the truck goes away. i currently have 109,800 miles on the truck

 

[JLandry]

JFrey,

That actually sounds like it could be normal behavior. When certain conditions are met (low coolant temp, low air temp, the brake pedal has not been pressed), the ECM shuts off 3 injectors so the remaining firing cylinders will generate more heat and help warm up the engine faster. It sounds counterintuitive, but it must work or the mode wouldn't have been implemented by Cummins and/Chrysler.

If you absolutely hate it and don't want it to happen, I'm pretty sure a dealer can disable it using a StarScan tool. I know on the 2nd gen trucks it definitely can be disabled using a DRBIII tool.

Drive safe,

John L.

 

[AH64ID]

Do it shutter if you manually put the rps at 1000 with the TPS?



I don't think its a TPS issue as thats not in play with auto fast idle. Most likely its a injector, but without a scan tool its hard to diagnose. If it continues to happen you may have to take it to a dealership or a shop with the ability to conduct injector tests and monitor rail pressure.

JFrey,



That actually sounds like it could be normal behavior. When certain conditions are met (low coolant temp, low air temp, the brake pedal has not been pressed), the ECM shuts off 3 injectors so the remaining firing cylinders will generate more heat and help warm up the engine faster. It sounds counterintuitive, but it must work or the mode wouldn't have been implemented by Cummins and/Chrysler.



If you absolutely hate it and don't want it to happen, I'm pretty sure a dealer can disable it using a StarScan tool. I know on the 2nd gen trucks it definitely can be disabled using a DRBIII tool.



Drive safe,



John L.

He has a CR, CR's do not have 3 cyl fast idle.

 

[JFrey]

thank you for your help. i was unaware that there where only 3 cylinders firing during this operation. also i will check next time im in the truck to rase the rpm's to 1000 to see if the problem persists.

 

[AH64ID]

thank you for your help. i was unaware that there where only 3 cylinders firing during this operation. also i will check next time im in the truck to rase the rpm's to 1000 to see if the problem persists.

As I already stated there is no 3cyl idle in 3rd gens. Its not an option, and doesn't happen.

 

[cerberusiam]

started my truck this morning is was 28 degrees. so it auotmatical go to fast idle at 1000 rpm's. then the truck starts to shake like it is missfiring.

That definitely isn't normal, and, CR's don't have a 3 cyl high idle so it should be smooth.



Like was suggested try it with accelerator and se eif you get the same issue. Might be time for some injector tests.

 

[p-Bar]

How about the FCA Fuel Control Accuator put some 2 stroke oil in the tank see if it smooths out

 

[BLoging]

kinda sound like what my 2oo4 is doing with 66,000 and i think it is the FCA from what i haved looked up on information.

 

[macdaddy]

started my truck this morning is was 28 degrees. so it auotmatical go to fast idle at 1000 rpm's. then the truck starts to shake like it is missfiring. is it possible that i have a bad injector, Fueling problem, dirty injector, TPS. and when i depress the brake it comes back to the norm 750 rpm. and the shaking of the truck goes away. i currently have 109,800 miles on the truck

Mine has done this since new. Never really pay much attention to it anymore. The idle always seems to smooth out. I think it might be from some small amount of injector fouling from idling too long while the motor is cold.



I always try not to run the truck unless I plan on driving it long enough for it to get up to full operating temperature. The 05 now has 97K.



Mac

 

[Wingate]

started my truck this morning is was 28 degrees. so it auotmatical go to fast idle at 1000 rpm's. then the truck starts to shake like it is missfiring. is it possible that i have a bad injector, Fueling problem, dirty injector, TPS. and when i depress the brake it comes back to the norm 750 rpm. and the shaking of the truck goes away. i currently have 109,800 miles on the truck

I see in your sig that you have an aftermarket intake... did you do a grid heater delete? If so, it could just be incomplete combustion...

Also, try removing the predator temporarily...

 

[JFrey]

yes i have removed the predator awhile back. and i did not do the heater delete, tried to duplicate it by pressing pedal to reach 1000 rpm. cannot duplicate it. i have started using lucasfuel treatment again. hopfully that will help.

 

[JaredH]

As JFREY has noticed my truck also exhibits the same High Idle - Rough Idle.



1) Does not rough idle every time the truck goes into High Idle mode

2) I have/do run Diesel Kleen (or some other fuel additive, used Lucas (non-combustible) for a while until I pulled the injectors and there seemed to be alot of soot build up on the tips - more on 4-5-6) since day one

3) Grid Heater is still in place

4) I tested injector leak/CP3 leak both in spec injectors 75ml/min (spec < 180ml/min) pump was ~650ml/min (spec <1000)

5) truck has ~93K on it, the rough idle just started this winter



I have not tried to induce the problem by using the pedal to rev to "High Idle. "



No other issue have been noticed with idle, performance, etc.



Anyone replace the FCA and solve this? Other ideas?

 

[cerberusiam]

When did you install the cam?



The built in high idle some odd ball things in it that are not always evident. Specifically, under certain conditions the ECU will split the main event in 2 and induce a lope to the exhaust.



ANY changes to the OE configuration (ie prgrammer, cam, etc) has the potential to enhance the lope to the point where it could actually shake the truck.



If it is only noticeable on high idle and not thru the pedal its a good bet its a combination of factors including ECU programming that is the source.

 

[JaredH]

The cam was installed two summers ago... Last winter it did not exhibit the rough idle characteristics.



I also did not mention the edge since it is only supposed to modify the fuel/timing after the engine reaches operating temp (172*).



The rough idle occurs below and above 172*



The cam profile optimizes the power stroke by keeping the exhaust valve closed a few degrees longer... . which if the main event splits into two events under "certain conditions" that could influence the engine idle... and possibly a lope. BUT, as I stated - last winter the truck did not exhibit the rough idle.



So with that I can only assume that the ECM did not decide this winter to change it's Algorithms, that stated the same goes for the edge.



If the combo IAT/MAP in the manifold is giving erratic output, then would that cause the rough idle?



Reason I mention this is that my overhead console MPG calculation seems to be creeping upward even throughout the winter (23~24mpg). I have read that when the IAT/MAP sensor develops a dead spot or begins to fail this mileage mis-calculation begins to occur.



Thoughts?

 

[p-Bar]

FCA troubleshoot = pour 2 stroke oil in the tank it lubricates the FCA

 

[JaredH]

Can do... So you feel that even though I run an additive (diesel kleen) the two stroke will lube above and beyond?



Any input on the IAT/MAP sensor guys?

 

[cerberusiam]

If the combo IAT/MAP in the manifold is giving erratic output, then would that cause the rough idle?

Its electronic, ANYTHING is possible given the right conditions. Same with the Edge, as long as it is connected the potential for influence is there.



When this whole loping idle splitting the events thing came up a couple years ago it was all over the place with occurences. Some trucks reportedly did from new, others just started at times after a dealer flash, others without a flash, and others never do it with\without a flash.



The only thing so far that is confirmed is the ECU some different stuff on high idle as opposed to idle up or throttle input. As TCDiesel is so fond of saying: these CR's don't conform to logic only experience.



I would guess as long as the return flows on injectors and IP look good, mpg is consistent, and no oil contamination run it 'til it dies. :-laf

 

[JaredH]

Alright... Oil is in... lets see if a lil 2-stroke smoke helps!

 

[Elite1]

My 03' had this same problem, stumbling bad at idle periodically... tried the 2-stroke and it smoothed it out. Ordered the FCA Fuel Control Accuator, installed it... (not real easy, suggest lots of liquid wrench on the three bolts and let it soak for a few days) The torx bolts were a real beech to get off! Finally got them off, installed the new part and now the truck runs great!
This is why I love TDR, look up a similar problem in the search section, then find the fix... Thanks guys!