Blue smoke at idle, but with a twist!? - PeachParts Mercedes-Benz Forum

Goldenvoice · #1 10-21-2010, 02:39 AM

Ava is our beloved 1982 300TD - 617, with 345,000 miles - my main PA hauler for over 3 years. Yearly, I adjust the valves, diesel purge, change filters regularly - and oil, etc. She's always been a very sluggish driver, nominated the "Worlds most gutless car".

Long story short, last year restored compression to the 360 range in all cylinders, (thank you Andrew) then recently had the injectors rebuilt, then finally found the lack of power to be a bad ALDA.

So, I was hoping solving the ALDA issue may also take care my next biggest concern - terrible blue smoke at idle, and often beyond (no, really, blue smoke means oil, and she uses plenty, so I knew the ALDA wouldn't have any effect, but still I hoped

Anyhow, tonight, while driving the stoplights in town, and watching the huge embarrassing cloud of smoke behind me, I made some interesting notes.

Ava "tends" to idle rough. But not always. But often, a steady lope-lope-lope-lope, and blow clouds of smoke. I noted today, if I increase the idle (with my foot) from 750 to 900 or 1000, the lope goes away, and often the smoke does too.

At the first stoplight (smoke is real obvious with headlights behind me), I let Ava idle and smoke, then watched as she blew a gawd-awful smoke screen behind me through 1st and 2nd gear, then quit smoking almost entirely as I leveled out in 3rd at 35mph...

The next stoplight, I held the idle up to 1000rpm = no smoke, then pulled away when the light turned green, and observed little or no smoke...

Very strange. I'm wondering if anyone else has noted similar issues with smoke.

Myself, I'm thinking it's time for Turbo work. I gave it a feel the other morning, cold, and can wiggle the shaft side to side enough to get a little audible 'clunk' out of it...

Thoughts?

mach0415 · #2 10-21-2010, 03:51 AM

Mine is doing the same thing. I was starting to think turbo seals, although loping will probably not be cause by that. I am leaning toward injector issues on mine, as mine does smoke at idle until warmed up and both irregular skip and smoke goes away. If I were you, I would consider a possible injector issue as well. Which injectors did you go with? There is plenty about Bosch quality issues here on the forum. I would have them tested to be sure.

layback40 · #3 10-21-2010, 04:26 AM

Maybe valve guide seals ?

47dodge · #4 10-21-2010, 06:30 AM

At a higher idle you are keeping the combustion temps up a little higher and burning the oil better. Same thing happens on my tractor, just set the hand throttle up a little and it will clean up the exhaust.

How did you get the compression up? If you honed and put new rings in, I would not expect the oil to be coming from bad rings, so valve guides, or turbo seals. If you did not hone and put new rings in but just soaked them, and they loosened up enough to get good compression, then I would say the oil ring may be rather weak.

W124 E300D · #5 10-21-2010, 06:50 AM

if you've done compression etc then rough idle is injectors, injection timing or injection pump

toomany MBZ · #6 10-21-2010, 10:08 AM

Quote:

Originally Posted by layback40

Maybe valve guide seals ?

I'll agree, perform a leak down test, this will let you know if that or the rings are the issue.

gastropodus · #7 10-21-2010, 11:09 AM

What did you do that restored the compression? Marvel Mystery Oil soak?

Kurt

barry123400 · #8 10-21-2010, 12:41 PM

First I would loosen one fuel injector line at a time to establish if the smoking is one cylinder specific. Just let it idle for enough time with each cylinder disabled to see if there is a difference.

Next if the condition seems to not be an individual cylinder remove the boot from the turbo and idle again. This just establishes it is not some odd turbo seal problem. I know it does not sound like the turbo. Except for the large cloud of smoke on acceleration. That may be an indicator of picking up from the pooled accumulation of oil . If it is also wet with oil in the boot is of course another indicator. It should be dry.

I am also not an expert.In fact very far from one. Still I would think on a serious leaking injector issue the smoke would be black rather than blue. On that basis I would put off an injector checking again at least until the two tests where done.

Posting the oil consumption rate of this engine could also be an aid to figuring what may be the possible cause.

kerry · #9 10-21-2010, 12:57 PM

Does your vacuum pump vent into the air cleaner?

znuh · #10 10-25-2010, 04:36 AM

Totally having the same issue here, so any light on this would be fantastic.

Smoke is blue/white and reeks of unburnt diesel. Car just crossed 369,768 miles (1982 300SD). Started to stumble and run rough at idle; what used to be a barely glow car to start has turned into something that does not want to start in 50 deg. weather.

Symptoms are the same, huge cloud of smoke at idle, and part throttle. Get on the highway, all smoke stops. Go back to idle, and whammo, fog machine.

Mileage has also suffered; I think I managed to barely get 20mpg at the last fill up. No access to a compression tester, but the car's power is just like it always is on the highway, and she takes off quite smartly.

I'd be very, very curious to see if this boils down to an injector issue, valve stem seals, or what have you.

Please keep us posted!

-James

t walgamuth · #11 10-25-2010, 05:29 AM

Unburnt diesel will smoke light blue.

Never look at your smoke in the rear view mirror at night. Even a good running diesel will look smokey under those conditions! Look in the daytime.

Of course smoke looks worse in the lower gears, your engine is turning (pick a number...) four times for a given distance compared to what it does on the highway, it does not have a chance to dissapate as fast.

And a miss from lack of compression whether it is from ring seal or valves will always be most prevelant when idling, as the rpm picks up the seal will be better as the leak does not have as much time to dissapate your compression, plus at higher rpm it is just harder to feel a slight miss.

And yes, I too am interested in what was done to improve compression.

And I would ask what oil you are running?

Just some general thoughts....

Ether · #12 10-25-2010, 10:09 AM

I had very similar symptoms with my SD. Installed new valve guide seals and the problem went away.

Goldenvoice · #13 10-30-2010, 02:51 PM

Sorry for the delay - way busy week with the wife opening a new store, etc + I wanted to observe Ava a bit more.

OK, I run Delo 400, usually 30wt. I've been a bad shade-tree-mechanic, and have not logged oil consumption, but will start in earnest with the next oil change.

A year and a half ago, we thought we'd start at the top, and checked compression - it was all across the board, something like 240-360. A valve adjust, and running the main fuel filter full of AT fluid brought 4 cylinders into the 360 range, but #1 dropped to 150psi!

Biodiesel300 had me soak #1 for a few days with a couple ounces of brake fluid, and that brought all cylinders within the 345-360 range. This may be a key.

I also know she's in need of a set of glow plugs, and have the plugs and reamer on order.

Wondering: could the rack dampener being faulty or out of adjustment create a smoking issue?

***So, for example: last evening, after a gig, we started her up, and drove about 6 blocks to the grocery store. I waited with the car - running, while my wife shopped. Sat in the lot for 10 minutes - temp gauge at 60 (half warmed up) Idling beautifully, and not a puff - absolutely NO smoke, or anything - I couldn't see any exhaust at all - very well lit lot - smooth idle - wonderful.

Then out on the highway 14 miles and stopped at her store - Ava sat chugging and smoking.

Keep in mind there seems no consistency to the issue. Sometimes she smokes cold...

I have a hard time believing that bad rings come and go, but maybe they do. I have new glows coming, and also plan the valve adjust and purge, although the latter 2 have not affected this issue much in the past...

?