560 SEL Rough Idle (Another one!) - Page 2 - PeachParts Mercedes-Benz Forum

hbofinger · #16 06-13-2002, 07:15 PM

moedip - Turns out there are no screens inside the fuel destributor on my '89 560 SEL. Just went and checked - nothing. Maybe they changed them in '89, which would explain why Phil coud not find them.

I'm back to square one. I had really hoped that this would take me closer. I am beginning to worry its something more fundamental, like a stretched/worn chain or bad valves. Somehow I think my fuel lines are fine.

amg280 · #17 06-13-2002, 09:42 PM

If it was a bad valve, it would show up when you islolated each cylinder. Its unlikely that more than one went bad at once. Look at your vacuum lines real good with the air cleaner off. There is one in particular, near the intake, that is like a U shaped. This one is known for coming off, and it will make a rough idle and will make ur exhaust note seem like a muscle car at idle.

Im not sure at what it does but its worth looking at, even though im sure you probably did this already. Other than that, it may be a bad fuel distributer. Had one on mine, after weeks of trying to find the culprit. They are somewhat hard to diagnose. If you have any new developments let me know, Id be interested in hearing them. I feel your pain, trying to diagnose a bad idle on a mercedes is a difficult and expensive experience, as it is discouraging.

Gook luck!

-Andy

hbofinger · #18 06-14-2002, 08:04 AM

Andy -

How about a bad cold start injector? The idle is rougher when cold, then cleans up as the engine warms up, though it's still a touch rough then (as described in the beginning of this thread). If it's bad and leaky, it could still be making the fuel mixture too rich randomly as it shoots fuel into the manifold after the engine heated up. Does that scenario make any sense?

#19 06-14-2002, 09:19 AM

Henry - Since you have no screens - I'd still put a fuel filter in the line by the distributor to catch any contaminants from the fuel line - good insurance if there is rust that will also protect your fuel distributor. My car sat for four years before I got it - water could have been sitting in the lines to cause my problem. Was your car sitting for a long time? In trying to solve my problem - my change list included: both fuel pumps, fuel filter, accumulator, idle valve clean, new distributor cap and rotor, new wires, new plugs - make sure you use copper NOT platinum plugs - as they can cause rough running, vacuum lines checked for leaks, compression test, air pump replaced, egr valve changed and I can't remember what else! I had the timing chain changed on mine with no difference. I took it to Mercedes for a diagnostic and got a clean bill of health. Still had the miss - until the lines were changed.The only other thing - if it acts worse cold - is the idle valve - have you taken it out and cleaned it real good with brake cleaner? If not clean it with brake cleaner until there is no more crud coming out - make sure the piston moves freely - then spray the inside with a coating of spray silicone and let sit for an hour for silicone to dry then reinstall. Before I cleaned my idle valve - the car had a buzzing sound from the engine when it was left sitting for a month and then started - as the engine warmed up it went away - cleaning the valve stopped that.I know your injectors are new - but if you have a little dirt from the fuel line getting through to them - they may need to be cleaned. I'd put the fuel filter into the fuel line by the distributor and pour Techron or other strong injector cleaner into the tank and drive it looking for an improvement in a few hundred miles.Keep me posted - I REALLY do feel your pain and will try to help.

hbofinger · #20 06-14-2002, 10:52 AM

moedip -
So you just went to an auto supply store, got any old in-line fuel filter, cut the rubber part of the supply line, and just inserted the filter with some hose clamps? Sounds like a 10 minute job. And this won't reduce fuel pressure or bring anything out of spec? Could be an effort well spent.

I am still curious if a bad cold start injector could have anything to do with this. Also, since cleaning the idle air valve does not take buying any parts, that could also be an effort well spent. You said spray it with silicone - do you mean a silicone lubricant, such as silicone door spray?

One thing I noticed is when the engine is cold, the idle speed fluctuates (I described this earlier), then settles down as it heats up. I can clearly hear a "clack-clack-clack" sound coming out of the front of the valve train in cycles - it comes and goes with. This sound continues in cycles even as the idle speed settles. Which is why I suspect a bad chain (It takes 8 revolutions of the chain to go through, so if a bad area of the chain passes It could be throwing the timing off, confusing all that lovely digital technology.) That's why I fear the whole thing may be out of whack.

It has plenty of power, it's only the idle stuff that drives me nuts!

#21 06-14-2002, 11:52 AM

Yeh - the clear silicone spray you would put on doors and rubber.I just used it as a dry lubricant for the piston. For the clacking sound - 2 things - how many miles on the car? Timing chains are usually good for 200,000 miles - the plastic chain guides and tensioner are the real problems to look for on this and the 420 engine. They should be done every 100,000 miles for peace of mind. The plastic guides and tensioner are cheap and if you do a search on this site Mike Tangas posted a real good article with step by step instructions on changing them. I think my tensioner and guides came to about $70. I changed my chain at about 160,000 miles and found I didn't have to - there was no stretch in it at all - when I held it by one end and lifted it it had the same amount of sag as the new chain. I don't think the clacking is chain though - more likely lifter sticking. Is it always there? always the same cycling? or does it clack in cycles and disappear and come back again randomly? I only drive my 560 occasionally for fun - not daily - if it sat for a month or so and I ran it - I had a little clacking sound on the passenger side bank from a lifter that went away after a 2 hour cruise. I used a can of Wynn's upper cylinder lubricant in the oil (says it quiets noisy lifters) and it slowly went away. - For a couple of bucks worth a try. If the noise stays there afterwards - then suspect chain or guides. From what I have read -normally chains make noise when cold and just starting up and tends to get less as the engine warms.Mike's article tells you what to look for on the plastic guides before changing - if I remember right - if they are the color of beer bottles - change them - new ones are white.
As for the filter - how can it change the fuel pressure? Once it is in the line nothing else is different. One suggestion though - I don't know the fuel pressure on this car - just check and make sure the new filter will operate at the pressures of this system whith the supply store you buy it from and you should be home free.

hbofinger · #22 06-14-2002, 12:12 PM

moedip - I really appreciate your advice.

the clacking sound goes in cycles - comes and goes. Warm or cold.

This car has 98k miles....

I've been reading Mike Tangas's adventures of rescuing a 560 from the junkyard. Quite amazing.

You think I'd be able to find an appropriate filter at TrakAuto?

One thing I know is if you've got one problem, you can usually get to it deductively. If you have two, you'll go crazy. My next steps will be:

1. check the wires at the idle control unit
2. install a clear fuel filter (also to monitor condition of the fuel line)
2. clean the idle air valve as you described

Any way I can test the cold start injector? In one post on this site a person pulled it, left it attached on the side, and then plugged the hole (of course with the car completely warmed up), and then started the engine.

#23 06-14-2002, 12:43 PM

Don't know on this car but on Vw gas jobs we pull the fifth (cold start) injector out of the manifold and crank the engine with the high voltage lead to the distributor removed with the engine warm and aim the injector into a glass jar and watch for leaking. With the electronics on this car I would be hesitant to do that as I have learned from experience that the spark generated can reach 1 1/2" in length (Mercedes always seems to overdo it!)So I would agree with plugging the manifold hole and seeing if the injector is leaking with the engine warm. If the injector was not supplying fuel - the car would have starting problems -which is not the case - so a cold check is not required.
Was you car sitting for a few years in the past?
I would go with your 1-3 ideas first and put in stong injector cleaner in your tank or that $20 stuff in a metal can by Duralube or others called fuel system cleaner and conditioner - That stuff is what I used when I got about 100 miles with no missing - now that I remember (Bear with me at times - as I get older I forget somethings until my memory gets tweaked!) and drive for a while. If there is any dirt in your fuel distributor - it will also clean it as well as your injectors. I have learned a long time ago -sometimes the solution is very simple - but you get too complicated and miss the simple things.
Check this site for what the fuel pressure is coming from the accumulator and ask the guy at the counter if the filter will work at that pressure.
I just finished putting in a rebuilt engine and tranny in my son's car and will be finishing it off this weekend - bet I know where you will be!!!

amg280 · #24 06-14-2002, 08:45 PM

On the drivers side inner fender wall, down above the AC receiver drier, there is an ignition control unit. It has a vacuum line going to it. MAke sure that line is still there. It will be near the ABS motor. Worth a shot, since we are covering every avenue. I know it will idle weird with that hose detached.

As for the cold start valve, hmm, honestly not sure, but If it still does it when warm, maybe not. Another thing I was thinking of, since you said the engine flucuates...is a bad intake gasket.

Since you said the idle gets better when warm, maybe the engine expands, and thus sealing most of the leak, which would explain why it idles rough when cold. Although I never seen one go bad on these cars before. Oh well, worth a shot. Try spraying some carb cleaner around the intake when its cold and idling funky. If the idle jumps, you have a leak.

Keep me informed,

-Andy

hbofinger · #25 06-17-2002, 10:58 AM

moedip - I could not find a clear gas filter that would be up to spec with the fuel pressure. I checked several stores - one flatly said they're not aware of any clear ones that are up to spec. Which one did you put in yours?

Andy - I checked that vacuum line - it's connected. Bought some carb cleaner to check for other vac leaks and try out your theory of a bad intake gasket.

On a speperate note and off - topic, I can't find any of the approved oils (basivcally avaiation hydraulic fluids) for lubricating the throttle linkage. Has anyone substituted any of these, or know where to get them in the states (or where to order some on the web)?

#26 06-17-2002, 11:40 AM

Hi Henry - If you read my post - I JUST thought of it - putting the filter in - I didn't put one in mine as I changed the fuel lines. Even if you can't see though a metal one - it will still filter out any dirt from your lines. Then, once in, if you use the fuel system cleaner in your gas tank and drive a couple of hundred miles - it will clean out your fuel delivery system and anything cleaned prior to the fuel distributor will be trapped by the new filter and the filter in the back of the car. Also any dirt in your injectors will be cleaned by this stuff and you should be OK. Very inexpensive to try compared to some of the things you can do and might solve your problem. Also -has you car been sitting for a long time(year or two or three) or has it been in continuous use for years. You must remember that at higher engine revs minor things will not show up as much as the more critical levels for a maintained slow speed idle. As I said before - don't start getting complicated until all SIMPLE things are tried. I do remember that when I put the fuel system cleaner stuff into the tank with my old lines - smoother idle did not occur until I had used about 1/2 a tank and after about 100 miles the missing returned. If you want a stonger solution for more cleaning power - add the stuff when you have about half a tank and drive it until near empty. The worst that could happen is nothing - the best is - the idle problem will be solved and with the added filter may not return - even if you leave the old lines in. What have you got to lose??

hbofinger · #27 06-17-2002, 05:11 PM

moedip -

Well, I did the first part of your recommendation at this point - cleaned out the idle air valve. It's drying right now. A ton of crud in it. Fairly easy job, though. Only takes a few mintues to pull it.

Next I will go (again!) and look for a fuel filter I can put in. Running cleaner through the system now.

I have no idea how long this car has been sitting. All I do know is that right after I bough the car I found a mouse nest on the left hand side of the air intake - nestled between the air cleaner cover and the intake manifold. No fried mice, however...

#28 06-18-2002, 08:38 AM

Mice don't build in a moving car! - You confirm my suspicions - the car sat for a long time - you probably DO have rust in your lines. Once you have the filter in - then run the car with cleaner - so any crud it breaks loose will be caught by the filter not the fuel distributor. Keep me posted.OH - make sure the piston in the idle valve moves freely before re-installing it.
thanks
Maurice

hbofinger · #29 06-18-2002, 10:34 AM

Maurice -

I don't know what happened, but the car is smooth as glass at this point, both warm and cold. Not even a hint of roughness when warmed up - symptoms are ALL gone. RPM's are a touch higher.

Here are all the things I did since I started this thread:

1. Checked all vac lines - nothing
2. Added oil additive to clean out valve train
3. Added injector cleaner to the fuel
4. Went to the idle control unit. Removed it. Sprayed the bottom contacts and the plug with Radio Shack TV tuner cleaner
5. Thoroughly cleaned out idle air valve with brake cleaner, and lubed it with silicone spray. It needed it.
6. Re-checked plug wires for the umpteenth time. Found one not 100% pushed in (oops!)

Well - live and learn. I know it could not have been in the plug wires originally, because the problem existed when I bought the car, and I then replaced the plugs and wires. But still, it COULD have been No. 6 above as a new cause. Again, as we say in IT, one problem - you'll figure it out, two problems - you'll go crazy.

Still, I am going to look for a fuel filter. Sounds like a good piece of preventative maintenance, and that fuel distributor is expensive.

Anyhow, this car runs like a true charm. You can hardly tell the engine is running.

Maurice - thanks for all your help. I don't think I would have tackled the idle air valve without you telling me how to do it, and it was a simple thing to do.

Another resolved issue on the mercedes shop forum!!!

#30 06-18-2002, 11:04 AM

You are welcome Henry! BUT -T-T-T-T -- don't rest easy yet! I was fooled on mine. Wait a week or two and I will bet my bottom dollar that it will start to miss again - in say about 100 - 200 miles. The injector cleaner cleaned the injectors and the idle is good - unless you replace the fuel lines or put in that second filter - the dirt will again build up in the injectors and you will be cursing - wondering what went wrong! If you put the filter in NOW and add a little more injector cleaner to the gas when you have the filter installed - then I will agree that you have the problem licked! Look at the bright side - It cost me over a $1000 dollars and two years of trying things to get rid of that gremlin! - You got it resolved in less than two weeks!!! CONGRATULATIONS!!!
Maurice
PS - by the way - I have a new gremlin on mine - thought I had it fixed but I don't. Last year I drove my car to my mechanic friend's house and shut it off and was talking to him beside the car when this big plume of white smoke came pouring out from under the hood. The smoke came from the rear of the passenger side of the engine. When we had the hood up - we saw oil was dripping onto the back of the exhaust manifold. Looked like a valve cover gasket leaking. Ordered a new valve cover gasket and put it in - only AFTER the engine reaches operating temperature does the smoking start again but not as bad and gets worse when you make a left hand turn. Just looked at it again last month - took the valve cover off and cleaned the sealing surface of the head - checked the valve cover for warping and replaced the gasket again - I wiped off the residual oil from the manifold and started the car up - when the rest of the oil had burned off I shut the engine off. I started it the next day and brought it to operating temperature - no leak! Success - NOT. Everytime I take a left turn the smell of burning oil permeates the inside of the car - straight driving - nothing. I looked at the rear of the valve cover and again it was wet with a little oil. Frustrated - I loosened the valve cover and pushed up towards the fuel distributor on it and pushed it towards the front of the car - then tightened it. Thinking that I would get a better seal at the rear. No Luck. Right now I am down to only one thing. The valve cover gasket that was on the car and worked for 2 years before the smoke and the replacement one my mechanic friend got me were aftermarket. I notice that on the sealing edge of the gasket that it flat and about 3/8" wide and near the outer edge there is a slight raised round bead on the gasket that looks like it squashes down as you tighten the valve cover to give an extra secure seal. I am trying to find out if the Mercedes orginal gasket has two raised beads - one near the outside and one near the inside which should give a better seal. When I get to the bottom of it I will let you know. When it happens - the white smoke scares the devil out of you! Keep an eye out for this one. The smiling faces are for the top part of this post - could not figure out how to put them there so they are here!!