jonUF02

I replaced the rubber seal from the air intake elbow to the throttle body. I thought I ordered the one from the MAF to the elbow, but it does not quite fit, that one seems to be just slightly larger than the one to the TB. I also replaced the o-ring behind the TB when replacing. Of all rubber pieces I have inspected and replaced, this one does not seem bad or brittle.

I am very confident that the trouble is not the motor mounts. I checked them thoroughly, and I'm pretty sure previous owner replaced them. I also tried the test with the jack supporting the engine. I know what broken motor mounts feel like, I have experienced it before. At some point I will try anything though. I have probably read every thread on the internet concerning these issues and the go-to argument is always motor mounts or MAF.

I will be doing the compression test soon, hoping results are positive, and replacing all the plugs at the same time. The coils have been ruled out and confirmed by fancy MB computer.

If anyone has a diagram of vacuum systems for this engine (from WIS?) please let me know. I want to make sure I have checked all of them.

jonUF02

Yesterday I found that one of my new crankcase breather hoses was cut, I must have damaged it during other work, and making a sucking noise, possibly throwing off idle with unmetered air. I fixed this up and then found that the water pump was making a noise and wobbling. Now replacing water pump.

This is strange because I checked this before. The idle shake started when my radiator started leaking and giving coolant low warning. I replaced the radiator, but did not see the wobble in the pump as I saw in a Youtube video / forum post. Now it is happening. I also replaced the belt, idler pulley, and tensioner recently, but did not feel anything wrong with the pump while I had it apart. Took the pump off and the bearing is obviously bad and loose.

Maybe this is the original problem, maybe just one more thing to fix... we will find out.

jonUF02

Water Pump is installed, along with a couple new vac lines and temp sender that I broke in the process. Still have the shakes.

Compression test and spark plug swap tomorrow.

I'm considering changing the motor mounts just because they are cheap compared to everything else I have replaced.

jonUF02

I did the compression test, engine completely cold, I removed one plug from each cyl. and disconnected the injectors and fuel pump fuse. I ran the test a couple of times on each cylinder, cranking about 5-6 times, lowest reading was 163, highest was 178. I believe this is a very good report. I also changed all 16 plugs and used a fuel pressure tester to verify fuel pressure on the rail is at 60 psi when running. Fired it up and no change, still shaking.

My "new" used exhaust had one of the secondary cats start to rattle, so I had them both deleted. I like the new sound.

I replaced the motor mounts yesterday. The old ones were not bad, just a little dry, still shaking on idle.

At this point, I am totally out of ideas. I have checked everything: fuel, air, spark, compression, exhaust. It runs smoother than ever, except when at idle.

GatorMB

Hey Jon,
The compression test results sound real good considering the engine age.
I didn't review the entire post since you are pretty good at covering the bases but,
a vacuum gage teed into one of the main manifold vacuum ports will give an engine health status as well.
A healthy engine will have 18-21 inches. The needle should not fluctuate or surge.
If your readings are below 18 inches then spray some carb spray around the intake manifold mounting area. Might be a small intake runner leak.
Note: use caution around the coils while performing this test, a leaking plug wire will start a fire!!! keep an extinguisher handy if there is doubt.

Gator

jonUF02

I just read through this blog from MarcusF regarding the intake manifold being dirty.

http://www.marcusfitzhugh.com/CLK/DIY/intakerepair.html

I had to remove the very top portion of mine when doing the fuel injectors because one of the o-ring retainers dropped down into the top of the valves. i saw that the intake channel was very dirty like this. Not sand, but quite a bit of general dirty oily burnt stuff. I assume this is normal for an engine with high mileage, but maybe worth taking apart the intake and cleaning thoroughly. I'm not having the extreme issues, codes, stalling, or acceleration trouble as described in this page, but maybe worth an afternoon to clean this out properly.


Gator - can you get me a diagram of vacuum lines from the WIS? I plan on testing as you suggested.

CurYousGee

Good work Jon been reading your tread, not sure if my shake is like yours at idle, but mine went away a few weeks after my spark plug change which you are doing next, but it did not go away right after, I also replaced my MAF, all O2 sensors, new fuel filter, and cleaned out the airfilter.

I have 90k on my car currently

jonUF02

Yep, I've done all of that. Can't figure it out.

After reading some more about the intake manifold design on this M113 engine, I think my next step will be to grab the entire manifold from the junk car I have been using, then clean it up and rebuild it thoroughly before installing to my car. I want to minimize any down time from road bumps that might be encountered in taking mine apart. I think I can pick up the spare intake manifold for about $50.

Andy11UK

Just read through the post while its slightly different to my issue on mine 320 always had a slight shake then one day out of the blue starting shaking itself apart couldn't drive it, leave it and it would be OK drive for a bit and it started again, made worse if you gave it some right foot, same codes, misfire and bad cats,

Fix was new plugs and leads, it had happened before and Merc replaced 2 leads, I know you said leads looked new but I'd look at a cheap set and swap them to test, they are "really" hard to get them seated corrected need to click on both plugs and coils, and very easy to be damaged on installation,

jonUF02

I have no codes. The engine is running very sweet now, except when it drops to idle.

I considered replacing the wires, but that is another $160 with no guaranteed fix. I'm satisfied with the condition of the wires, just as I was with the motor mounts that I ended up replacing to no avail. I have removed and replaced them from the coils and plugs multiple times in the process, so I'm sure the seating of them is not the problem.

This nagging problem is really driving me crazy. There is no concrete evidence of the problem, no codes, nothing to go on.

jonUF02

Over the past couple of weeks the shaking at idle has slowly subsided to a barely noticeable state, but still there. I am moving forward with my plan to clean a spare intake manifold. I am posting a pic of the spare I picked up from a donor car. You can see it is completely BLACK inside, and the flaps were totally stuck, I'm sure that mine looks similar inside. Cleaning off the carbon deposits is a time-consuming battle. So far I soaked it with engine degreaser, washed it off, then started with the top half and a few cans of carb cleaner. It is mostly clean now. The bottom half has a lot more odd surfaces and those flaps. I decided not to disassemble the internal parts because they are glued together, and I don't want to compromise that. I am going to scrub and soak as best I can. I started using a brass wire brush on the bottom half. It would be nice if I had access to media blasting equipment, would make the process much faster with some soda blasting. I'm afraid to take it to a machine shop for soaking because of the plastic parts and sensors that are permanently attached.

I think this will definitely wake up some lost power due to all the deposits, and it's likely that my flaps are not closing at high RPM as they should. I think the core issue may be one of the small vacuum hose passages through the manifold that could be clogged with these deposits. I haven't been able to get a vacuum tester and test the lines on the car yet. I will continue with the refurbish of the spare intake manifold and see the difference when I'm done.

If I valued my time a little more and my money a little less, it might be worth buying a whole new assembly for just over $1000. The one vacuum line at the front that is not replaceable is really a design flaw and small point of failure for the whole assembly. You can read about that on some other forum postings for the M113 engine. I decided to snip the end of the hose and splice in mostly fresh hose, then plasti-dip the remaining hose that can't be replaced for safe measure. Some have ported and polished the entire assembly, but I don't have the time or patience to go that far.

jonUF02

Here are the after pics of cleaning the intake:






Notice I had to use a bead of RTV to put it back together, Mercedes does not sell the gasket, this is supposed to be one complete part. I used about 10 cans of carb cleaner and rags, then gave a final bath in a plastic bin with dishwasher detergent and mixed in a large pot of boiled water to get it hot. Some residual carbon came out with the bath. I used some all-purpose oil on the butterfly valves and linkage so they move freely now, and a pipe cleaner to make sure the vacuum ports were clean. I also took apart the spare EGR and cleaned it thoroughly. It looks really clean now. I can't wait until I get the time to swap it out and see the difference.

jonUF02

PROBLEM SOLVED!

I installed the refurbished intake / egr / TB combo that I cleaned up and now she is purring again. No idle problems.

My best guess is that one of the vacuum passages was clogged up and causing the issue.

I have a spare intake manifold if anyone wants to buy it. I'm not cleaning it up because it was pretty time-consuming. I also have the egr attached and 2 more spare throttle bodies.

After all this work she should be good for another 100K+ Almost everything peripheral to the main block has been checked, cleaned, or replaced.

jonUF02

Another quick tip I learned -

If you change your throttle body, you will need to reset engine adaptations.

At the end of this work above, I used the TB that came with the spare intake and noticed that my acceleration was not as sharp as before. I just swapped back to the previous TB and it feels stronger again. It seems each TB is a little different, and the computer is adapted to it.

f250

How much for your Spare intake Manifold? Or were can I reach you at?




Notice I had to use a bead of RTV to put it back together, Mercedes does not sell the gasket, this is supposed to be one complete part. I used about 10 cans of carb cleaner and rags, then gave a final bath in a plastic bin with dishwasher detergent and mixed in a large pot of boiled water to get it hot. Some residual carbon came out with the bath. I used some all-purpose oil on the butterfly valves and linkage so they move freely now, and a pipe cleaner to make sure the vacuum ports were clean. I also took apart the spare EGR and cleaned it thoroughly. It looks really clean now. I can't wait until I get the time to swap it out and see the difference.[/QUOTE]

johnnr

Nice work!

Not surprised the dealer's diagnosis was incorrect either. They are rarely accurate on things like this, especially when you don't have codes for them to look up. The techs are not analytically inclined...they rely on their darn computers.

Seems like you still dropped a big dime into this though. But great you got all working good now!

jonUF02

Mostly this cost me labor and frustration that I could not find the problem. I started with the cheapest things first, other than the exhaust. I paid $500 for the second-hand exhaust, and then another $100 for someone to cut out the secondary cats later. The rest of the parts were probably another $500, but I was not keeping track. This is far less than the dealer's $3200 bill to replace the exhaust and O2 sensors, which would not have even come close to fixing the problem. If I paid someone for all the time I spent, It would not even be worth fixing, probably more than half the value of the car, or the whole car when you add up all new parts from the stealership.

Pagz

well done sorting your idle problem!

I have your exact symtoms on my c43 and have checked over the entire system to no avail.

fortunatley I have a spare manifold from my 5.4 , I think I will open it up.

in the end which part of the manifold do you think was causing the vaccum leak?

cheers,,

jonUF02

I really have no idea what was causing this, I can only assume that one of the 5 or 6 small vacuum connection passages was clogged, or possibly something with the EGR system. I cleaned it all. I also swapped the manifold from the junk yard complete with the EGR and front pressure valves and switch attached, so it could be one of those things which were also thoroughly cleaned.

I'm getting an extremely slight burble again, but nothing like it was before. I plan to pressure test all these vacuum lines and connections to the manifold some day, but not really bothering me at this point.

The one very stupid design flaw is that the vacuum hose coming from the bottom front of the manifold cannot be replaced although it gets just as brittle as the other hoses. I coated it with liquid plasti-dip and cut it down to about 1/2 then spliced in some new hose.

Pagz

Hmmm, is there an internal chamber which links all the runners together for vaccum accumulation? If so would the glue sealing the runner joints effect the amount of vaccum the chamber recieves?

The manifold off my 5.4 has the brittle hose as you describe, but my 4.3 is still really soft with no cracks. So I will definitley pull apart the 5.4 one for a play and see if I can design a better vaccum hose.

Also, Just a note on Marca's page, the sand he found in the intake is probably carbon bits from EGR(looks like dust and sand coated in oil)...the small amount of actual sand will be what has dropped in when he removed the manifold.

brauhaus313

For posterity's sake, after the rough idle disappeared, did the engine seem to perform better overall? Now that it's been several months since you did all the work, has the rough idle returned?

jonUF02

The engine did not perform any differently during the problem, only the idle. When you hit the gas it ran just fine. I think the intake cleaning might have made performance just a hair better.

After some months, I still notice a tiny shake in the idle most times, I have tried everything I can think of to get rid of it, but it is not very noticeable as it was before, feeling like the car was going to stall out or something; intermediate violent vibrations. I still get no codes or lights, I'm just living with it until some problem indicator appears, which may never happen, it might just be like that forever, it seems to be common with these V8's. No other problems with the car at this time, she runs great.

gregory13lil

Damn good job finding the issue and reporting back. I will be doing the same soon.