Sudden Rough idle

[moclovflop]

Hey guys, you were very helpful with my previous question about air in the lines, that seems fixed, so time for round two.

Over the last couple days I've noticed that the car has a very rough idle when cold or warm. I know diesels rattle, but this isn't what it was doing only a week ago. This is very hash and dense. Not the typical clack clack clack of the normal idle. It seems like everything in the interior is about to shake a can of paint.

Performance doesn't seem to be affected, still revs and does highway speeds like normal. But at highway speeds, the pedal certainly is very foot-numbingly buzzy.

As Mentioned, this happens when cold or warm.  I've read a few things about a possible stuck injector or air in the injector that needs to be bled out. And I'll be cracking the nuts this weekend to see if it could be something like that, but the injectors were rebuilt less than 2000 miles ago. Doesn't look like injector pump mounts, and the motor mounts are also fairly new. It definitely seems mechanical.

 I would think a misfire would be pretty obvious based on what I've experienced with gas cars, so I don't think that's it, but I don't know.

I might grab some diesel purge for the tank and maybe change the fuel filter, but again, lots of previous Maintenance has been done (filter is less that 2000miles old, tank was dropped and cleaned, injector pump was cleaned), so I'm not sure if that's where I should be looking.

On another note, the cold start lever doesn't seem to do anything to help when cold other than reduce smoke. No idle change, no notice change in anything. Is this normal? Should there Be something that obviously changes when it's in use? It is connected and does move the arm on the pump.

Let me know your thoughts. Last time it was an easy fix, I hope it's the same this time.

Thanks again.

[vanbcguy]

Can't remember what year your car is...

The cold start handle starts having a noticeable impact on idle (as in it raises the idle speed) starting in the mid to late '80s.  Cars before that don't have the idle bump, the cold start handle just alters the timing slightly at idle.

What's your idle speed set to?

[moclovflop]

Sorry, 1981 Caddy.

I don't have a tach or a pulse adapter for my timing light, so I'm not sure what it's set to. Is there a way to check it without either of those?

Idle speed doesn't seem to have changed, it's just harsher.

I'm thinking a bubble might have made it's way to one of the injectors after my whole "air in the lines" ordeal.

I was thinking or raising the idle a bit before this all happened to try to take the edge off of the diesel rattle, now it may have to be mandatory until I figure this out.

[vanbcguy]

You can pick up a handheld photo tach fairly inexpensively but I wouldn't bother unless you have something else you'd find it useful for.

Good chance you've got an engine mount on its way out. But you can play with the idle speed a bit and see if you can find a happy spot - go for the lowest speed that doesn't shake too much.

[moclovflop]

Here's kind of a weird thought, is it possible for the throttle arm to slip on the shaft? As in, it slowly moves itself to a lower idle after a while?

I ask because I feel that my idle screw is adjusted a bit much. I still have normal throttle range, and can do highway speeds no problem and acceleration isn't bad. But does this look a bit over extended to anyone?

I adjusted it again to help with my rough idle issue but am not sure about when I should be thinking there may be other issues. Adjusting the idle is simply covering up something bad.

Note, however, that I don't have a high idle with how it's set, hence my question. And again, I don't seem to have any power issues or throttle response issues.

[moclovflop]

So, cracked the nuts on the injectors to bleed them to see if that has anything to do with the issues. Idle dropped on all cylinders so at least I can assume no dead injectors.

It seems to have helped a little bit with the idle, but I noted something that probably isn't helping my cause. On cylinder #1 (or #4... which ever is passenger side) I noticed bubbles coming out at the base of the injector near the head through the diesel that had ran down there when bleeding.

Obviously this needs to be addressed (I don't have a wrench that would work in the tight spot), but could this be a major player in the idle game? What issues would this create that are noticeable? black Smoking? Bad MPG? anything?

I ordered a Bentley manual that will be here Tuesday, so forgive my ignorance in the mean time. But what is associated with something like this?

Can I fix it with a new heat shield? Is there a copper washer or gasket that might be bad?

Please note, though, that the motor was bone dry before I cracked the nuts. No diesel has been seen in that area, so it doesn't seem like it was leaking out any fuel. Just air.

Additionally, there are air bubbles entering into the overflow lines between injectors. The bubbles seem to be coming from inside the overflow nipple, so I'm assuming they still have a good seal, but will be replacing them just in case. Is that normal to see air flowing into the lines? I know them being empty is normal, but not active bubble flow... Thoughts here?

ALSO: Please see the video below for what I'm talking about with all of this. I know it seems a bit like rambling. I'm still a novice.

http://youtu.be/KNdWF8lYPis

[EcoTX]

Using clear lines between the injectors is kind of silly, there is no point really. 
Air in those lines doesn't mean anything, completely disregard it.

The air bubbles at the base of the injector I wouldn't be super concerned with either.
Probably just isn't torqued down quite enough and with 400+ PSI pushing up, you will get tiny, tiny amounts of air and see a bubble if diesel has leaked there.

I've seen those tiny bubbles coincidentally on that cylinder too in my car, it doesn't effect anything.
You could try a new heat shield if you want and torque it down to 55 ft-lbs if it bothers you that much.
I usually go 5-10 over because I like things snug...I wouldn't worry about that tiny bit of air though, it is nothing.

There are no copper washers or gaskets, only a heat shield at the base of the injector.

Your car sounds great, sounds like a healthy diesel.
Drive it and enjoy it 

[TylerDurden]

I generally agree except for one thing: the leaking at the base of the injector is hot combustion gas, which will cook the injector nozzle and likely bugger the threads making the injector very difficult to remove. I'd put in a new or reformed heatshield.

[CODE4LS1]

I have also experienced the "buzzing" effect on the throttle pedal.  I found it to be a combination of failed motor mounts, and all the exhaust nuts were backing off the head, causing even more vibration.  Hope this helps.

[moclovflop]

Thanks guys, I'm still trying to hunt this down and it seems to be getting worse. Seems like everything inside the cab is going to dance out the windows when I start it up.

Motor mounts were done about 2000 miles ago, so they should still be good (hopefully). Fuel filter was done this weekend, along with a fresh oil change.

And it's developed a misfire on cold startups if the cold start knob isn't pulled out. It's not a constant miss, but every few seconds it'll do it. Pull out the knob and it stops.

Also, it is a lot more lumpy of an idle once warm, like I'm I've got a small block with cams (though obviously not as pronounced, it still has the whomp-whomp-whomp-whomp sound)

I haven't adjusted the idle since adjusting it about a month ago, so obviously something is slowly getting worse. And although bumping up the idle with the gas pedal smooths things out, it still doesn't sound clean, it isn't the smooth pitch that it was only weeks ago.

I'm leaning toward bad injectors even though the idle dropped on each one. Perhaps they are pumping, but very poorly?

Also thinking of rotating the pump a hair towards advanced to see if that helps.

Again, it's great on the highway with very decent power, only smokes with wide open throttle, and it's black, not white. And it's not a ton of smoke. No smoke at idle or partial throttle/cruising speed.

Always starts immediately on the first bump, cold start lever or not. So glow plugs and compression seem to be OK.

ONE MORE NOTE (sorry...) Exhaust seems to be getting louder?? But all clips and nuts seem tight.

Thoughts? What else would cause a degrading comfort level over the course of weeks.

Thanks in advance.