Question about a vehicle with a hood...

I am using the off topic part to ask this question in this location. There are so many sharp people here, I am hoping someone will come up with something to help solve a problem that has stumped an experienced mechanic.

We have an '87 Mercedes 560sl with 110,000 miles. It had sat a year or more undriven after the previous owner had issues with it not wanting to get up to speed. It was very lightly driven before being parked with only a few thousand miles put on it in several years.

Before parking, previous owner replaced the fuel pump (Chinese, not Bosch) and lots of other stuff and nothing fixed it. We purchased it, towed it to Mercedes mechanic of over 20 years and he had it a long time before finally re-lining the tank. In the process, the fuel pressure regulator and fuel distributor? were also replaced. It was assumed that crap from the tank was getting into the fuel system and re-lining the tank fixed the two previous failed attempts at making it home with replacement fuel system parts.

The car ran well for a bit, but then started running poorly/sputtering a bit at idle. My wife described it as the car not going forward at times from a stop with your foot off the gas. Cars normally continue forward with no gas, but it was "heavy" and was taking more effort to go from a stop. The problem is/was sporadic. It was running fine at speed.

She took it in, two weeks later, they say nothing to worry about and that it's one of the best running 560's in town. Perhaps a vac leak which is hard to track down.

She drives it home and a day or two later it starts having problems at 65 going up a bridge. Won't go past 65. Below that, fine. Back at 65, hits the wall like a gust of wind. Shortly thereafter, the car won't go and she loses power where it's even hard to make the car steer (something we understand.) Towed to mechanic, can't find anything wrong other than the idle sputtering a bit. He's driven the car all over and I've run into him, so I know he isn't B.S.ing me.

They've had the car more time than we have. Great V-8, just can't get the kinks out.

Any wild guesses?

.

It might be the catalytic converter.

Another thing you might want to check is the coil. It may be breaking down when it gets hot.

Duane in Tennessee.

Should mention that the mechanic did notice a slight sulfur smell when running rough,leading him to believe it was running rich (I think.)

The Cat converter will have that smell and as it get stopped up worse the smell will intensify. It will eventually smell kinda like rotting eggs. Usually when the cat converter is bad though the engine will lose power & get worse as the cat continues getting more stopped up. I wouldn't rule out the cat being bad but if it still has good power & will still maintain a high rate of speed when driving it the cat is ok. I am pretty sure that a honest service center that does inspections can check the exaust discharge & tell you if the cat converter is bad.

Just from experience with some newer autos=?? Have the catalytic converter checked for blockage -even the entire exhaust system too. Ive seen exhausts systems have a partial blockage fron loose parts & even colapsed exhaust pipes- yes - those from some factotys have a second wall of pipe inside the outer pipe & can colapse & prevent exhaust flow.Remember =air in - air out- Have a muffler shop check it out= likely they have experienced this many times also. Happy Mercedesing

Guys, good info. I can tell you that the exhaust system was replaced and looks good and I can't imagine they didn't replace the cat along with the entire exhaust. P.O. did all scheduled maintainence and wouldn't have short cutted anything.

Mechanic indicated he thought the slight sulfur smell was possibly a running rich issue. Suprised he wouldn't think Cat converter because even my novice self knows about that. When it was running rich and blowing black smoke previously, it smelled like "beer" to me.

Could the cat converter go bad from sitting up? The car certainly wasn't driven enough over the past few years and sat at least a year in a garage, and I don't think he ran the car during that time.

I should mention also that the mechanic has been driving the car and he had it up to 100 with no problems, so it will get up and go. Just can't figure out the intermittent issues.


My wife says that she had not gone through an entire tank of gas since first taking it in and getting it back for the idle problems. It has 1/8 of a tank remaining when it broke down. Of course, it ran when the mechanic tried it at whatever point after towing it (probably the next day.)

Also, when it was idling rough, the car's fuel efficiency gauge would indicate worsening efficiency the worse the car idled. Not sure what that tells us.

The cat converter has charcoal inside it and over time it will get stopped up from the exaust that it is supposed to clean. I am not a mechanic but would think that if the engine has been running rich it could cause the cat to get stopped up sooner than it should. They all have a life span & eventually need replaced & with a vehicle running to rich it will cause one to get stopped up a lot sooner. I don't think that with one sitting that it would go bad. If the the car is running rich there's a small chance that the cat could be the problem but like I said if it does not seem to be losing power and feel like it is holding back the problem is not the cat. T.P. is right the exaust has to breath & if it's stopped up one of the big signs of it would be it losing power. I have experienced bad cat converters before & when they was bad the car would not hardly run & when it's completely stopped up you will know it cause your car will just not go. The cat for that car cost big money so there could be a chance that the guy that owned it was a tight wad like me and refused to pay the money to replace it but if you have plenty of power & can get in the car & cruise highway speeds it probaly ain't the cat converter. I don't know if you are in a state that requires a vehicle emissions sticker or not but of you are a service center can check the cat converter or even a muffler shop as T.P. said.

It's is against federal law to remove the cat completely off of a car that has one & I know people not me:-(Lol) that have removed a lot of them & I mean quite a few of them over the years. Somehow they found a guy at a muffler shop that they got to cut them off & put a pipe where it used to be. The cat converters costed a lot back then so not knowing for sure that it was the cat converter they would have them cut off and put a pipe in their place. Sometimes the guy new for sure that it was the problem & sometimes he was not for sure. A lot of times it was the problem. It has been over 7 years ago.

As for a vehicle setting up a few years gaskets can go bad in the fuel system if it sits for a extended amount of time. Most all gas these days contain 10% ethanol & it causes gaskets & seals in the fuel system to go bad especially if the vehicle sits for a while so there is a good possibility that something with your fuel system has gone bad. The newer engines with throttle body & fuel injection systems has a fuel pressure regulator that when it goes bad it will cause the engine to run rich. I don't know much about the Mercedes but I would think that they have a fuel pressure regulator in them so it could be it. There are also map sensors, & the oxigen sensors that I previously mentioned that can also cause them to run rich. With all of the crap that engines has on them these days it could be anyone of them or even the fuel injectors. I am pretty sure that there are Mercedes clubs that have forums & I don't know if you have thought about it but maybe you can check some of them out & maybe someone might of had the same problem that you are having & can tell you what their problem was. Like I said I am not a mechanic and never claim to be I just try to give suggestions & info on some experiences that I have had with vehicles that I have owned & I have owned a lot of them. My uncle owned a car lot & I worked for him many years & later on in the late 80's I bought & resold vehicles for a living. I had many experiences with bad cat converters & most of the time when they was shot the car had no power. I am not gonna say its this or that cause I don't know but I will try to help in anyway that I can & share my experiences that I have had over the years with vehicles cause I think that that is what this club should be all about. Help, Advise & Infomation

HVM, thanks for all the input. The fuel pressure regulator was replaced as was the fuel distributor.

I actually posted on the MB forum earlier today and it's everything from cat converter, vac leak and still getting trash out of the system. The 560's really don't like to sit and that is the consensus. Someone also recommended a tune up, which I don't recall doing. Will let you know if we ever get a definite. Right now, it runs fine. It only breaks down on us...

Is your exhaust set up with an o2 sensor before and aft of the cat? if so it should throw a code out that will tell you that it's flooding (check engine light on). I am not sure if all catalytic converters are the same, mine has cadnium and one other type of mettle in it. I just replaced my entire system from the manifold to the tailpipe. Mine has 3 o2 sensors in the system. One on each manifold side and one after the cat. My cat melted and all the guts went into the muffler. Sounded like a potatoe in the tail pipe. But the worst of it was the cat melting inside do to a flooding engine caused by an o2 sensor not working, causing the computer to default to a 50/50 fuel air mix. I didn't realize that the cat was toast and I replaced just the muffler to fix the problem. BAD MISTAKE...the muffler exploded comeing home one nightwhile driving down the highway. Flooding engine aloowed unspent fumes to go through to the muffler and it eventially lit it on fire...KABOOOM. If it's flooding an o2 sensor could be bad causing the computer to default if that's possable on your vehicle.

Big W wrote:Is your exhaust set up with an o2 sensor before and aft of the cat? if so it should throw a code out that will tell you that it's flooding (check engine light on). I am not sure if all catalytic converters are the same, mine has cadnium and one other type of mettle in it. I just replaced my entire system from the manifold to the tailpipe. Mine has 3 o2 sensors in the system. One on each manifold side and one after the cat. My cat melted and all the guts went into the muffler. Sounded like a potatoe in the tail pipe. But the worst of it was the cat melting inside do to a flooding engine caused by an o2 sensor not working, causing the computer to default to a 50/50 fuel air mix. I didn't realize that the cat was toast and I replaced just the muffler to fix the problem. BAD MISTAKE...the muffler exploded comeing home one nightwhile driving down the highway. Flooding engine aloowed unspent fumes to go through to the muffler and it eventially lit it on fire...KABOOOM. If it's flooding an o2 sensor could be bad causing the computer to default if that's possable on your vehicle.

W, I believe there are at least two. My wife indicated as much earlier. The mechanic suggested checking that again since he replaced it initially, but it then again ran rich. He also suggested a sticking EGR valve. It won't breakdown on him..Not sure how rich, if at all, it's currently running. When it broke down the first two times before re-ling the gas tank, it puffed black smoke on hard accelertion and then lots....I witnessed it from behind the first time. Then it just loses power and doesn't go or have any power assisted steering.

Guys on MB forum said that a vac leak would make the fuel economy gauge go way over to the poor side, and it wasn't doing that when idling rough. This kind of stuff is the reason I never wanted a German car, but it's a beautiful ride, the wife loves it, and it was a great deal if we get it running consistently. If...

Well I no you probably don't want to here this but after my van sat for 2 years fighting over a claim to get the $9000.00 worth of hail damage fixed,(they refused to wright it off) it cost me another $3000.00 to replace all parts fuel related in order to get it to run right. injectors screwed, EGR sticking and worn out, pressure regulator, o2 sensors and complete exhaust, fuel filter, and just recently fuel pump. I owe my soul to this POS, I hope it is a better deal for you and you can get this figured out.

For those who are interested...

Guys on Mercedes forum suggested an "Italian tuneup" which means putting the car in 3rd (it's an auto) and letting the revs run high for an extended period of time. The car really can't blow things out because in order to rev high enough to do so, you would have to be hauling tail. I'm sure the car shifts before it ever is able to run the RPM's up high enough.

They also suggest a heavy dose of quality premium (it takes premium anyhow) and a couple of bottles of Techron concentrate with a bottle added each fill up for a year or so. This is the combined advice of several folks, including two whose same cars had sat up for longer than ours.

I may be way off but it sounds like a vapor lock. My 76 ford van would act the same way sometimes when it was hot. The good news is that the fix is cheeeeeeep. Put a wooden clothes line clip on the fuel line near the carburator. It absorbes the moisture.

Thanks, Dan. Not sure if this is relevant, but it's fuel injected. Vapor lock was not suggested prior but someone did suggest moisture getting in they system if removing the fuel cap caused air to rush in vs. out.

After reading the last post - the light went on - have you tried replacing the gas cap?? If its not doing its job- venting / non- venting that will also cause fuel delievery problems.

Twinpilot001 wrote:After reading the last post - the light went on - have you tried replacing the gas cap?? If its not doing its job- venting / non- venting that will also cause fuel delievery problems.

No, sir. But that's what is on the easy list and was suggested on the MB forum One for a Mercedes is probably $100..

before spending $100.00 for a gas cap, I would drive around without the cap to test it.

NOW YOURE =THINKING!! Good Boy!

Laz,
If you run the engine for a while & then shut the car off then remove the gas cap if it is bad there should be a lot of pressure in the tank. I kinda think that the gas cap is not your problem cause when the pressure builds up it will run bad all of the time. If there was any possibility that dirt dobbers could of got in the previous owners garage they could have also stopped something up with their dirt. The little turds are getting in my garage and have stopped the key hole up on the switch to my riding mower 3 times. Not to happy about it either they are around $30 a pop. They also stopped up the gas cap on my chain saw & I couldn't get it to crank after putting it up for winter. I don't know why they do it but the will stop up any little damn hole they can find. I don't know why but wasp's & dirt dobbers love getting in vehicles when they set a while.

Heres another thought to throw into the mix.
You think it runs rich when it acts up?????
When you open the fuel cap it is under a vacuum????

I am not a German car tech, But.... I am a German and I am a tech (sorry been a long day)

Anyway, Does the Benz have a vapor canister?
A common domestic problem is the cannister fills with fuel and the fuel gets pulled through the vacuum line into the intake = overfuel/rich condition.

That can happen two ways "topping-off" or a bad gas cap vent.

Brain fart......
An 87 should have a NON vented cap. Just as all new cars, Leave the cap loose on your OBD2 car, Get a check light.

None the less fuel in your vapor canister blocks the tank from venting back into the engine to reburn and puts raw fuel vs vapor into your intake......
Thats more like it.

try sea foam i love the stuff,dave