1984 300TD Turbo Euro, What To Do Next...Chasing a Rough/Smokey Idle Problem - PeachParts Mercedes-Benz Forum

hcubed · #1 10-12-2009, 12:03 AM

The car is an 84 300TD Turbo Euro. I'm the third owner and have had it for about 3 years. Odometer says around 190K, but it's slow, off by about 13% as checked with GPS, so the car might have closer to 200K+. It runs much, much better than when I first got it due to alot of work I've put into it, but it still has a smokey, rough idle that I haven't been able to get rid of. It also smokes at very low, constant speeds, other than that it runs great. The smokiness does not seem consistent either. It happens more often than not, but sometimes the idle seems just fine. Outside temperature doesn't seem to affect it. Normally it starts fine above, say, 25 degrees, but sometimes it stumbles a bit on the start. Again, not a consistent problem. It burns some oil, but it's not awful. Car runs at a consistent 80-85C.

What I've done that might aid in this discussion:
-air filter (this actually very recently and it made a huge difference in general running smokiness), fuel filters, diesel purge, fluids, belts, basics
-valve stem seals
-valves adjusted (again just yesterday, a couple tight ones, but nothing too bad)
-compression test (today, got 300-305psi on all cylinders in 8-10 cranks, not great, but not bad either)
-updated glow plug relay, new glow plugs, all tested and working fine
-cleaned glow plug holes of carbon with that special boring tool
-adjusted ALDA (I live in the Rockies at about 8,000ft - this was a must!)
-replaced leaky shutoff vacuum element on back of IP
-replaced all fuel lines (old ones were rusty and crumbling), checked fuel tank screen (it wasn't blocked with anything)

After much forum surfing, this is what I haven't done, but maybe should:
-I haven't ever removed or inspected the injectors/pre-chambers (I'm thinking I might do this next)
-have never messed with the injection pump (drip timing or rack damper or anything else besides the shutoff element)
-have not checked timing chain stretch or anything to do with timing (I think the chain is supposed to be changed around 200K so this might be an upcoming task)
-have not performed a leak down test
-still have the old fuel primer, but it doesn't appear to be leaking

So, my question is what should I do next to try and get to the bottom of this problem? It's kind of embarrassing when I'm at a stop light or idling somewhere and all of a sudden I'm surrounded by a big cloud of smoke. I'd really like to fix this issue, especially before the snow sets in...

Thanks in advance for your help and let me know if you need any more info.

Tripp

jkubica · #2 10-12-2009, 10:07 AM

Hi
I would lean toward pulling the injectors and having them pop tested and checked for spray pattern at an injector shop. Use new crush washers/heat shields when reinstalling.
Joseph

hcubed · #3 10-13-2009, 12:48 AM

Ok, so one vote for injectors. Thanks, Joseph.

Any other input? I know you master MB mechanics have lots of strong opinions

jt20 · #4 10-13-2009, 03:40 AM

besides the regular maintenance items that we all expect to be completed before you post a problem...

I would strongly suggest ruling out the Crankcase Ventilation System (CCV) as a source of oil burning or excess fuel.

Either vent the CCV to atmosphere for over 500 miles or install an oil/ air separator for 500 miles.

After either of these, the exhaust should smell more palatable and visibly less noticeable.

t walgamuth · #5 10-13-2009, 05:59 AM

Smoking what color? If its light blue that is fuel. Stumbling inconsistantly on start up sounds like a bad glow or two. I would revisit them and verify they are all working.

Injectors usually are not the culprit although often suspected.

I would pull the injectors one at a time and test them with a jumper cable to verify that they are glowing wihite hot. Be careful with them you could get hurt or start a fire easily. They cool of quickly though, fortunately.

#6 10-13-2009, 07:11 AM

T meant pull your glowplugs one at a time and test them. Not the injectors

dannym · #7 10-13-2009, 07:50 AM

I vote valve seals.

hcubed · #8 10-13-2009, 11:11 AM

Yeah, the smoke is light blue. The car normally runs fine on startup, although it does stumble some times. All the glow plugs are new and I just tested them this past weekend with a multimeter when I had them out to do the compression test.

The smoking normally occurs after the car is fully warmed up and is at idle or very, very low speed.

dannym, I've done the valve stem seals in the last 10K miles.

jt20, I have removed all the EGR stuff so the crankcase vents directly to the turbo intake on the air cleaner. Any ideas for an oil separator so I can try venting directly to the atmosphere?

Thanks.

jt20 · #9 10-13-2009, 11:57 AM

Here are some pics of mine. It was successful in relieving my smoke at idle and moderate throttle. It also sweetened-up the smell of the exhaust and its general opacity / color.

Some members that have done this are BGKast and ForcedInduction and their setups should still be posted together in a thread somewhere.

In these pictures you see an airplane grade air/ oil separator. The drain for the oil is on the bottom and is draining into a little plastic container. It looks like ***** but it really does what its supposed to.

Some units are Raycor and Mann-Hummell and can range from $150 to $400 new! This one cost me $20 shipped on E-bay and is not ideal, but sufficient.

You will want a unit that will not choke out your engine at higher speeds / loads so make sure to get the dimensions of the item before you buy, and make your judgements about the thing.

best of luck

jt20 · #10 10-13-2009, 12:01 PM

Quote:

Originally Posted by hcubed

Any ideas for an oil separator so I can try venting directly to the atmosphere?

Thanks.

You could vent directly to atm without the separator as a diagnostic test for a few hundred miles. Try to route it out of the engine bay, you will see it at stop lights and I personally find that embarrassing.

hcubed · #11 10-13-2009, 12:07 PM

Good idea. I'll just vent out without the oil separator for a bit and see if that helps things. If so, I'll use one of these:

http://cgi.ebay.com/ebaymotors/G-4023-AIR-OIL-SEPARATOR-NEW-SURPLUS_W0QQcmdZViewItemQQhashZitem2556c07ed1QQitemZ160369245905QQptZMotorsQ5fAviationQ5fPartsQ5fGea r

jt20 · #12 10-13-2009, 12:21 PM

did the fifth cylinder near the firewall have a weak compression reading?

I forgot this post was about a rough idle, forgive me.

hcubed · #13 10-13-2009, 12:23 PM

The compression readings were mediocre. 300-305psi across the board. Cylinders 1, 3, and 4 got there in 7-8 cranks and cylinders 2 and 5 took an extra crank or two.

jt20 · #14 10-13-2009, 12:28 PM

If you take a look at the rear end of the block, you might find a stream of oily goo dripping from the head down the block.

This is a headgasket issue. There is an oil channel there that leads to the head to feed the camshaft etc.. It leaks into the cylinder as well as leaking out of the block. This oil is burned and the compression on this cylinder is lower due to the poor sealing of the HG.

It is not critical, but it happens and burning oil on only cylinder will cause an imbalance in the engines running as will the lower compression number.

...just a thought

hcubed · #15 10-13-2009, 12:30 PM

There is definitely oily goo running down the back of the block. It's been that way since I've had it. I suppose this means a head gasket is in order?