Cold high idle rough

[Lil' Dog]

Now that its getting cold in the mornings I've noticed a rough running condition above idle speed. Basically the truck fires on the first turn and idles without even a rumble. Smooth as silk with very little smoke. But, if after a minute or 2 I bring it up to 1100 or 1200 RPM, it starts buckin and coughing with plumes of white smoke. Sounds like its missing. If I drop it back to idle it purrs. My 89 never did such things so its got me a tad concerned.



What could be the cause???





J-eh

 

[Case500D]

I have experienced the same thing

Lil'Dog,



I have experienced the same thing with my '92 before. Mine will do what you are describing, but then after a 20-60 seconds at a higher idle it will smooth out. And if I put it in gear it isn't as rough when the rpms come up. I am sure interested to find out what it is.



Jeremy

 

[EOliver]

Mine does this exact same thing... . Guessing combustion temps are too low to burn fuel any faster than idle... ?

 

[Lil' Dog]

Hmmph... Sort of glad to hear...



But, my 89 never did this. I could start it, wait for the oil pressure to stablize and then pull the throttle to 1100 and go in and make my lunch in the morning. I haven't got the throttle idea totally developed for this one yet, but I would like to do the same... Thinking of getting a high idle solenoid for a carb and installing a bracket/switch.



Any others????



J-eh

 

[R.E. Miller]

Thinking.

If I were you guys, I would check out your KSB soleniod and make sure that your grid heaters are cycling according to the manual. I know that on my 92 the KSB worked, but the sensor in the intake manifold was shot. When I fired it up like that and it was chilly out... look out white smoke and missing like it was a piece of junk... . it wasn't the sensors were

 

[Lil' Dog]

Everything seems normal to me. The heaters drain the batteries before startup, and cycle on the same sort of time as the ol 89. And when starting warm, it runs at around 700 then after a minute it pops up to 750-800 so the KSB is working.



It idles just fine, smooth as silk, hot or cold. Its just when you want to rev it up cold.



J-eh

 

[jakestrailer]

What is the KSB and what does it do?

 

[R.E. Miller]

The KSB solenoid increases the pressure inside the injection pump which advances the timing when activated. This helps lessen the white smoke and rough running associated with cold temps and start-up.



This thing looks like a brake light switch that kind of hangs off the pump.

 

[GOODE11]

Air

Hey guys had the exact thing going on w/ my 1 ton. It was air in the fuel filter. For some reason it wouldn't affect start up, but off idle it sounded terrible. Then it would take awhile for it to clear up.

On mine I replaced the fuel filter drain orafice, the fuel heater, and all the o-rings involved. Also tightened all fuel lines around the pump (hight pressure and supply).



The problem hasn't occurred since w/ about one year and 30,000 miles. With lots of idle time.



Don't know if this is your solution but it sure did help mine. It doesn't sound like an old 80's chevy 350 start'in in cold weather any more.

 

[andyr]

My 93 has done this since I've owned it in 97. Only does it between temps of 51* to 60*; below 50* heater grid comes on and I don't have any problems. I think the ksb valve is changing the timing for cold weather but the engine does not need it so it runs that way. The engine is quieter during this time also. Mine clears up after about ten seconds of driving and as soon as it comes out of it the diesel knock comes back to normal levels of loudness.

 

[Lil' Dog]

Well its time for an LOF before winter really sets in, so I have to pull the fuel filter anyway. I'll be sure to check for all the appropriate gaskets make sure its all clean.



Thanks guys.



J-eh

 

[CToney]

Rough Idle

Howdy Jason



I hope everything with your 93 is going good.



I had the same problem with my truck after I got the HO injectors. I lived with it for a week and then complained to DSG. They said that it was improper timing or improper washers installed with the injectors. I am pretty sure that the timing was advanced too much. My truck would idle terrible with lots of white smoke (unburned fuel)and would run fine once warmed up. I would get your timing checked out my guess is that it is the problem.



I hope this helps you out. Let me know what happens.



CR Toney

 

[Lil' Dog]

CR

Idling isn't the problem... It idles just fine. Very light blue haze for the first 2 min, then its clear until I put er into gear.



Just if I try to increase the speed to 1000 or 1200 Rpm in that first 2-3 min. then it starts buckin and coughin with white and blue smoke.



It really doesn't make any sense to me. Like I say, my 89 never did that even with 1 stuck injector LOL...



J-eh

 

[CToney]

More Info

Sorry Jason I guess I should have provided you with more info. It was about -20 C and I had my truck plugged in and just like you say it would start fine and then when I would idle it up to 1200 rpm it would be quite rough with lots of white smoke. After it had warmed up it would be fine. Took my truck into DSG and they adjusted the timing and it would not run rough or smoke as bad when cold. Replacing the block heater from one that was supposed to be 750w to one that actually was also helped the white smoke when -40 C. The yard would no longer get filled with a haze when my truck was warming up. It looked like the ole 4010 was running in the yard.



I hope this explains things better.



TTFN

CR Toney

 

[Lil' Dog]

4010 LOL... . My buddy had a 4020 that could fog the back 40 LOL.



Sounds like what I've got. I have been putting off getting the timing done until I get the injectors I want. The timing has never been adjusted so I'm sure its off by a few degrees if the valve set was any indication.



Thanks for the info...

 

[ERMiles]

Guys - reading your comments makes me wonder if changing injectors knocks your timing off. I got new ones this fall and I notice some of the same cold launching roughness you mention, which I never had before. Is this something I can do myself by rotating the pump - if so, what, exactly do I rotate and which way??

 

[Lil' Dog]

I'll tweek the pump, but timing I'm not comfortable with... I let the shops do it as they have the tools and the knowhow...



If you get a Cummins service manual, it should have all the right info. .



J-eh

 

[Lil' Dog]

UPDATE......

Well I finally got the timing checked out on this thing.



It was at 1° BTDC!!! . So they (GCL) set it up to the 10° spec and now I have No smoke at all cold!!!! at idle or at 1500 rpm. . WOW!!!Oo.



I suggest to all that if you have a the same symptoms I had, get your timing checked out. Worth every penny.



However my boost all across the board has dropped 2 #'s. At full load and on the highway. I hope this means same power, better MPG... . We'll see.



J-eh

 

[BushWakr - RIP]

Ok Lil Dog, make me ask... . what is your boost now

Hmmmm, wonder what would happen if you injected pure Oxy

Smiles, if you put in new injectors you should have timing checked properly anyway. I don't know the physics of this but it seems that they can theoretically effect timing "needs", but not change current setting. I think I can explain my irrationality if you like but thats a technical subject best left to the knowledgable.

My . 02



Regards, Bob

 

[Lil' Dog]

Bush



What used to be around 21-22 #s at full load (2300 - 2800) is now just touching 18 -19 #'s. Also where it was about 15 #'s at WOT 1500 Rpm, is now around 11-12.



Cruising at 115 KPH flat ground, little head wind is now 4-5#'s, was around 6-7#'s. Subsequently the EGT's have dropped as well.



I am concerned that the RWHP has dropped, but the accell and boost rise rate is improved, ie the boost comes on much quicker.



I really need to get some injectors... This stock setup stuff is still depressing LOL. . Is Piers's deal in CAD??? That price on the site is pretty impressive... Hmmm I have a gift cert to spend there that I won at the ABC Dyno day. .



Bush, I would like to just cut and paste the mods on your truck to mine... LOL.



J-eh