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- - Rough Idle (https://www.dieseltruckresource.com/forums/help-97/rough-idle-22161/)

I tried this in another thread before but don't believe that I got an answer that worked for me. The truck runs great, good power, good mileage. Sparadically it will idle rough. Sometimes it is totally smooth, sometimes a little sparadic miss, sometimes real rough. Air and fuel filters are clean, could be the winter fuel at some truck stops but don't think so. Cold or warm does not seem to matter. I see some real good knowledge about sensors here, any ideas?

Does the check engine light come on before, during or after the truck runs rough?The first thing that I would do is remove and clean the IAT Intake air temp sensor, the tip gets full of soot, even more so with the use of an exhaust brake. the computer uses this sensor to adjust idle, pump timing.

HID, Don't know if you are using any additives or if you've ever replace injectors but you may have an injector that's sticking intemittently or has some carbon on the tip that is causing the fuel to drip a little instead of atomize. You may try some of the Cummins injector cleaner and see if that helps.

I second Smoke Dog, sounds like a lazy injector to me. The low pressures at idle tend to show up a leaking or clogged injector. Try some good cleaner by LUCAS or maybe LUBETECH for a couple of tankloads to see if it clears up. Do you notice any smoke puffs from the misfires?? J-eh

I have some of the same symptoms. However, Cummins diagnosed mine occasional rough idle as a leaky injector valve. It seems to come and go. Some days, its a pretty good miss. Other days, is a nice smooth idle. Im hoping to get a new pump in the next few months. Rich.

O.K I looked in my manual from cummins here is a short list of ideas. 1 dont know why but check your engine mounts 2. fuel drain line is restricted. 3. fuelpump overflow vavle is malfunctioning. 4. fuel connector is leaking. 5moisture in wire harness connectoers. 6. ESS is malfunstioning. 7. lift pump or injection pump malfunctioning.8. injector. 9. fuel inlet restriction or supply line between fuel pump and injectors. 10. ECM problems you need to check for codes. Hope this can help

First I want to thank the great replys. Smokedog hit it on the head. I had cleaned the sensor, used Power Service in it and the problem persisted. I felt secure that it was probably an injector and had watched for clues that might wash down a cylinder, but no smoke and no engine light. I put a heavy dose of cleaner in it and the thing has not run so smooth in months. I did not realize that it was not that smooth pulling but it is a different truck. Has a hum to it now. Of course this is on one tank so I don't know if it will stay clear, might have to change and injector or two :) or six ;D What a chance to go for bigger injectors... and no wifey to question it. The problem is definately fuel related though. Could be the winter fuel, when it started, or dirty injectors, or both probably. Thanks much guys...

Hmmmmmm. Maybe 275s in the future?

[quote author=Haulin in Dixie link=board=13;threadid=9129;start=0#88124 date=1041655249] First I want to thank the great replys. Smokedog hit it on the head. I had cleaned the sensor, used Power Service in it and the problem persisted. I felt secure that it was probably an injector and had watched for clues that might wash down a cylinder, but no smoke and no engine light. I put a heavy dose of cleaner in it and the thing has not run so smooth in months. I did not realize that it was not that smooth pulling but it is a different truck. Has a hum to it now. Of course this is on one tank so I don't know if it will stay clear, might have to change and injector or two :) or six ;D What a chance to go for bigger injectors... and no wifey to question it. The problem is definately fuel related though. Could be the winter fuel, when it started, or dirty injectors, or both probably. Thanks much guys... [/quote] Try some Howes Meaner Power Kleaner you can usally buy it at truck stops, my Uncle told me about it he has a 2000 car hauler with the cummins 24V & the engine has a miss between 600-1000 rpms & when he puts this stuff it it smoothes the engine out & he gets 3mpg better also, so i figured I would try it, now my truck has no miss at all but I was amazed it seemd smoother & more powerfull also, & my lift pump was sounding kinda wierd latley since I put the stuff in it never sounded so strong! anyways I highly reccommend it! ;) Still trying to figure out why my uncles truck stumbles like that though.. i'm thinking injectors or he needs a valve adjustment, his truck has 330K on it & it runs like new! oh original lift pump! & it's still good!! tank is closer to the engine though that's the trick! DRecu!

Dracu, you bet, that is what I put in it. Great stuff... Cummins was closed and that looked the best if expensive as hxxx. Looks like I have enough for about four tanks at $22.95

[quote author=Haulin in Dixie link=board=13;threadid=9129;start=0#88390 date=1041726962] Dracu, you bet, that is what I put in it. Great stuff... Cummins was closed and that looked the best if expensive as hxxx. Looks like I have enough for about four tanks at $22.95 [/quote] Sweet! Glad it worked have you tried without it now? I am just using the stuff every tank because it pretty much pays for itself for the fuel milage increase I get & it seems very good on the injection system! Glad it's working! DRecu!

I have a similar problem MAYBE. I have noticed lately that when I am cruising at 40-50 MPH and just barely putting my foot on the pedal that it feels like it is missing. If I step on it I don't get the same feeling though. The thing is that I have used VERY regularly Stanadyne (for the most part) or Power Service. I thought that this would take care of my injectors. So does this sound like an injector problem? So I should use Howes Meaner Power Kleaner, LUCAS or LUBETECH?

sounds almost like your TC is shuttering or slipping.... when you step on it it unlockes so you would not have the prob. Just a thought DRecu!

My dad's 98 6.5L Chevy has a bad miss or something all through out the RPM range. If you leave it sitting for anymore than a day, it will hardly start. We've tried cleaner but it doesn't help. It's acting like it is getting air in the line. It keeps stumbling. We took it in the shop. After reading this, I'm thinking it's a bad injector. I should find out today.

I have been using that Howes meaner power Kleener for about a month now and have to admit it really makes a difference,man does that motor purr now. Definitely recommend it. Also a good idea to make sure fuel is treated if you're going to drive from warm to colder climates.Most truck stops will treat their fuel based on daily temps.Well i should say most decent ones. I have also been adding anti-gel additive from FPPF and between the two,plus the winter front,mine starts like its summer out and i see no smoke,warms up quick too. TGCTD