Rough idle

[Cincinnati Guy]

What can cause rough idle? I went through all my injectors and changed out just one that didnt make a sound difference when loose. Can my pump timing make it have a rough idle?

 

[HammerDown]

Ya know, I too sometimes get a not so smooth idle...and other times it's smooth as silk > and the reason I feel my MPG kinda sucks.
New BB's and Baby Moose ='s runs down the road great.

I would think (if) it was valve/lifter related/mechanical, it would do it all the time. I'm not buying a 'lazy' lifter as they usually get worse when the oil's hot and thinned.
I'm thinking it's one of Pensacola's 'new' BB's that need some work Almost feels like a loose belt vibrating...but it's not

 

[Cincinnati Guy]

I keep thinking its air intrusion, but wouldnt it be a bear to start then?

 

[HammerDown]

I keep thinking its air intrusion, but wouldnt it be a bear to start then?

When I lost my prime (when sitting over night) it was a bear to start...but ran great once it got the fuel.
I would think (if) you had a slow leak before the IP it would show a leak. If it was in the return side (as mine was) the caps were damp > and it only takes one bad cap/return o-ring to lose prime over time.
But then again, it could suck air too, as air is thinner than fuel.

 

[Cincinnati Guy]

Here is a little video. Sometimes it seems to have a rough idle then other times it dont.

http://youtu.be/eWY3CEIkjOA

Sound good to you?

 

[91dirtydiesel]

Ya know, I too sometimes get a not so smooth idle...and other times it's smooth as silk > and the reason I feel my MPG kinda sucks.
New BB's and Baby Moose ='s runs down the road great.

I would think (if) it was valve/lifter related/mechanical, it would do it all the time. I'm not buying a 'lazy' lifter as they usually get worse when the oil's hot and thinned.
I'm thinking it's one of Pensacola's 'new' BB's that need some work Almost feels like a loose belt vibrating...but it's not

X2, Pensacola "new" bbs ran so s***y at a warm idle for me, but anything other then warm idle it was good

 

[Trying my best]

Here is how to check for air intrusion

http://s1132.photobucket.com/albums...e Test/?action=view&current=101006_093531.jpg

Good luck

 

[LSOSGT1109]

I can't tell you by listening if you're timing is good or not but I do know that timing can cause a rough idle.

 

[Cincinnati Guy]

Now im starting to get a slight haze of smoke at idle. I just cantwin!

 

[vegas39]

X2, Pensacola "new" bbs ran so s***y at a warm idle for me, but anything other then warm idle it was good

Same way for mine, drives me nuts sometimes. My truck runs smooth and great in the mornings when the engines below 180 degrees.

I still have my old original stanadyne injectors, wonder if there is someone that might be able to do a better rebuild on them, as opposed to these POS Delphis.

 

[Trex]

I've got the same problem, was idleing rough when first stated till it warmed up ( maybe till it got all the air out of the system ) then it smoothed out. Now it's getting worse, when i first start her up she will run for about 30 seconds then die out on me, i guess the fuel filter run emptey. Have to really crank her to get started again. I'am assuming i am getting air from somewhere, havent had the time to check yet. I've read on here somewhere that if you take your fuel filter off ( before you try to start the truck ) and it's only half full then you have a air leak somewhere. At least that might narrow it down for you, then you would have some idea what to look for

 

[Dsl_Dog_Treat]

What color is the haze? Blue will get ya raw fuel and retarded timing which could give you a rough idle especially if the injectors are popping off at different pressures.

 

[LSOSGT1109]

Now im starting to get a slight haze of smoke at idle. I just cantwin!

Definitely starting to sound like a retarted timing issue.

 

[Agnem]

Na. Here's the deal. What is most likely happening is you have some leakers. When your idling, the fuel pulses are moving more slowly, and the pintle is being lifted off its seat slower, and not going up as far, so the spring doesn't slam it down into the seat as hard. Here is what happens... for the sake of discussion, lets assume the first injection sequence goes ok. Fuel gets injected at the right time and you get a smooth cylinder fire. As the ignition occurs, the cylinder presures go way up and the pintle lifts slightly off its seat due to a weaker spring. A little bit of carbon slips in and holds the pintle up ever so slightly. There is a slight amount of fuel presure still in the injection line, so as the power stroke ends and the exhaust stroke begins fuel is starting to bead in the seat. A droplet forms and falls into the cylinder. Now you have insufficient heat to ignite it completely, so it burns off as low temp smoke (blue haze). Now the intake stroke completes and the compression stroke begins. At the appropriate moment, the injection pump sends fuel under presure down the line to the injector. BUT... some of the fuel is missing. The presure needed to pop the pintle off its seat is missing, so the pump injection sequence ends before the presure needed to lift the pintle has been achieved. Or if it was achieved at all, it was achieved late, and a smaller fuel delivery occurs resulting in a weak firing cylinder. Now you have a bump in your idle. The cylinder strokes continue, and maybe the pintle is leaking again like before, or maybe not. Maybe the next ignition occurs and the stars are aligned and you get a valid properly balanced ignition, and then maybe you don't. So you can see with a leaker you get uneven unballanced power strokes. As fuel delivery and engine speed increases, the sealing characteristics of the pintle start to change, and you can end up with an injector that is working fine producing a smooth running engine. But when things drop down to idle again, the bad injector characteristics re-emerge, and drive you crazy.

 

[Cincinnati Guy]

Mel you described it perfectly! Im sure injectors are the problem, I need to hurry and send them to Russ...