Stumble at cold start

[jman]

I have been fighting this issue for quite awhile now. I only have the stumble on a cold start. It will start great the rest of the day. There is no long crank issues at all. If it is plugged in it starts normally. If not it stumbles when it starts. It runs great, mileage is great, power is normal. This started at 80K and I'm at 104K now. Chyrsler and I are trying to work it out since the problem was documented at 80K and "can't be duplicated at this time".



I have an occasional rough idle, and a surge with cruise control. The rough idle doesn't happen often, but comes up now and then, but smooths out in a few minutes.



Any ideas.



TIA

 

[MickeyMiller]

JMAN,



I'm following this thread with interest. I have approx. 95K on mine and I've had 4 times in the past 5K miles where I experienced a rough idle on cold start up. Goes away after a few minutes. Patch of bad fuel? Dirty injector? Valve adjustment? Failing lift pump?



Mickey

 

[betterthanstock]

Do the interior lights dim intermittently? That would indicate that the heater grids still work.

The FCA on injection pump may need cleaning /replacing.

The fuel filter has an electric heater built in. Does it still work? Need an amp meter hooked up to test it. ( No code will set if it's bad. )

 

[PBrauer]

https://www.turbodieselregister.com...2436-how-long-does-take-your-truck-start.html



Post #12

Interesting how the link ended up abbreviated...

 

[Cattletrkr]

I only have the stumble on a cold start. It will start great the rest of the day. There is no long crank issues at all. If it is plugged in it starts normally. If not it stumbles when it starts. It runs great, mileage is great, power is normal.

Yep, I drive a diesel too. It happens when they're not new anymore. Unless your stumble is bad enough that you think it's going to die, then it sounds normal to me.

Mine kicks, bucks, belches smoke, and I think it might even swears at me when the weather turns colder. Ususally only takes a few seconds for it to clear up and all is good. On the really cold mornings (sub zero) it'll maybe last a minute or so.

 

[jman]

I'm leaning towards the FCA also. This all started when my idle started sticking at 950-1000 rpm occasionally. The grids still work as the headlights still dim and the volt gauge still cycles. It doesn't idle rough at start up it just stumbles a bit when it fires. No white smoke at all. I think it may be time for new batteries also. Four and a half years and 105K miles may be nearing the end of the battery life.



The reason I lean toward the FCA is because of the sticky idle, and the cruise surges like crazy now and then on a down grade. I can't think it can be anything to bad since it started with 80K and now we are at 105K with great oil analysis results, great mileage, etc.

 

[PBrauer]

The idle probably isn't "sticking", the ECM is idling up for some reason. If it's not cold when it happens then you need to check your oil pressure... one of the things that can cause/trigger it.

Regardless of the oil analysis, I'd change the stock filter and see if it stops idling up.

 

[Cattletrkr]

Dad's '03 had similar issues that a new FCa helped out for a little while. He has a really rough idle when the high idle kicks in.

 

[daytripper63]

I have a little over 62k miles on my 03 and mine started doing this around 53k and after trying a bunch of different things and it continued to happen, then I was reading here on TDR about fuel additives in which I have used Stanadyne performance formula since day 1 but on the post here it rated down the list a ways for lubricity quality so I changed to Stanadyne straight Lubricity formula cause it came in at #4 on the list and was easy for me to get, thats when things got interesting... The stumble stopped happening!

So you can try this if you like since it seemed to work for me, But now my question is, DO I HAVE AN INJECTOR HANGING UP WHEN ITS COLD FROM LACK OF LUBRICATION OR ? and by changing to the lubricity formula I have bought some time?

 

[rbattelle]

The idle probably isn't "sticking", the ECM is idling up for some reason. If it's not cold when it happens then you need to check your oil pressure... one of the things that can cause/trigger it.

I don't think low oil pressure can cause an idle up. The ECM has no idea what the engine oil pressure is - only that it's greater or less than 6 psi. If it were <6 psi, the factory gauge would peg on "0" and there would be a "Check Gauges" light and all sorts of "dinging".

Here's a good "stumble" thread, although I'm not sure your stumble is related to JSteiger's.

JMan, is your fuel pump on the filter canister? I've had mine stumble very bad at idle only twice, and both times it was due to a lift pump issue (air in the system both times following lift pump maintenance).

I have a theory (emphasize theory) that some of these '03 and '04 trucks with idle stumble *might* be related to the fact that the lift pump shuts off after 2 seconds when the key is turned to "run". Then when you turn the key the rest of the way to "start", the pump turns on again. I've always thought that might cause minor starting issues, especially if there's a slight leak in the low pressure side somewhere. It could send a "slug" of air through the CP-3 which would cause a stumble. Or the low-side pressure could drop when the pump shuts off, and a weak factory lift pump has trouble pumping back up to full pressure when it comes back on. The effect *might* be exaggerated in cold weather.

I think it's rather telling that sometime later (2004. 5?) Cummins changed the ECM programming to keep the lift pump running for up to 30 seconds while the key is sitting in "run" before the engine is started. This guarantees maximum available pressure and flow at the CP-3 inlet when the engine starts - no delay while waiting for the lift pump to build up pressure and volume.

Ryan

 

[daytripper63]

I don't think low oil pressure can cause an idle up. The ECM has no idea what the engine oil pressure is - only that it's greater or less than 6 psi. If it were <6 psi, the factory gauge would peg on "0" and there would be a "Check Gauges" light and all sorts of "dinging".



Here's a good "stumble" thread, although I'm not sure your stumble is related to JSteiger's.



JMan, is your fuel pump on the filter canister? I've had mine stumble very bad at idle only twice, and both times it was due to a lift pump issue (air in the system both times following lift pump maintenance).



I have a theory (emphasize theory) that some of these '03 and '04 trucks with idle stumble *might* be related to the fact that the lift pump shuts off after 2 seconds when the key is turned to "run". Then when you turn the key the rest of the way to "start", the pump turns on again. I've always thought that might cause minor starting issues, especially if there's a slight leak in the low pressure side somewhere. It could send a "slug" of air through the CP-3 which would cause a stumble. Or the low-side pressure could drop when the pump shuts off, and a weak factory lift pump has trouble pumping back up to full pressure when it comes back on. The effect *might* be exaggerated in cold weather.



I think it's rather telling that sometime later (2004. 5?) Cummins changed the ECM programming to keep the lift pump running for up to 30 seconds while the key is sitting in "run" before the engine is started. This guarantees maximum available pressure and flow at the CP-3 inlet when the engine starts - no delay while waiting for the lift pump to build up pressure and volume.



Ryan

I doubt its the fuel pump or lift pump since I am running the FASS 150

 

[jman]

Well I changed the FCA and it did seem to smooth out the idle and quiet the acceleration noise. What I found though is I only get the stumble when I let the lift pump run for the 25-30 seconds. I ended up with the reflash that allows the lift pump to run the entire time and not run the 3 seconds and shut off. I did a couple of quick restarts and all was well, then I let the lift pump run until it cut out and then started it and it stumbles. My problem seems to be related to the length of time I let the lift pump run.



Anybody have any ideas. It may not be the cold to blame, but the fact the pump is running while I wait for the grids to cycle.



BTW-The FCA didn't help the sticky idle at all, so that is still a mystery, but I can live with that.