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I was checking out my air filter in my new car which is running bad. It starts but often not easily and it drives fine although not much power. It runs best at higher rpms and interstate speed but pickup is awful. I will likely be taking it to a professional for diagnosis but wanted to try a few things myself. In reading all day online I saw the suggestion make sure the air flow is good and filter is clean.

I checked the air filter and it looks pretty new. There was junk in there on the outside of the filter which I vacuumed out but it was not much. In taking it apart I am taking a look at what I suppose is the air flow unit and beginning of the fuel injection system. Part number is Bosch 0438120115

See picks below- Can I clean this? If so with what and how? Can I spray something in directly to clean things downstream?
I obviously am new to this car and just a good learner, not a mechanic. Is this normal for the valve to push down and stay down on this? Every picture I see online of these has the valve up. Mine is too but when I push it down to take it look it stays down.

Also - any other DIY things to check with slow starting and sluggish driving? I hope I did not buy a lemon here, it looks beautiful and was pretty regularly maintained but I am afraid I overlooked more than I intended in my buying decision...

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Congrats on your purchase scb71, and I'm sure the car will be running fine soon - that said the current challenge may be caused be any number of things and there are / aren't easy fixes.

The round plate you're pressing down should come back to the top on its own. Please don't spray anything into the chamber below as that's where air meets fuel. You could spray EZ starter or ether etc. if you had issues starting up to help troubleshoot, but that's not the problem here so don't be tempted. I see the fuel distributor (the round silver device in your first pic with 6 fuel lines coming out on top of it) looks fairly new, do you know if the previous owner had it replaced / refurbished?
 

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Discussion Starter #3
I don't know if it was replaced but don't have any records as such. I do have some other records but not that.

You suggest not spraying anything int here - oops. I sprayed some carb cleaner and then some seafood spray in there and wiped out some gunk with a shop towel. I did spray some in there while it was running but there was no smoke or anything like those crazy seafood videos you see with smoke blowing out the exhaust. I didn't spray much but the round plate does move freely now and returns when pressed down.

The car runs ok but starts slowly, not all of the time but often. I also think it may start slower after driving it as opposed to hone cold but I would need more data points to verify that. It just seems like it has no life. I get that this is the inline 6 and not the larger 560 V8 but I cannot imagine it is supposed to be this slow. I hope not anyhow. There simply isn;t any pickup. It almost feels like it just isn't getting enough juice when the pedal is full down.
 

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I don't know if it was replaced but don't have any records as such. I do have some other records but not that.
That's a pity. Is it possible to check with the PO? Was the car running rough all along or is it an issue that's surfaced recently?

You suggest not spraying anything int here - oops. I sprayed some carb cleaner and then some seafood spray in there and wiped out some gunk with a shop towel. I did spray some in there while it was running but there was no smoke or anything like those crazy seafood videos you see with smoke blowing out the exhaust. I didn't spray much but the round plate does move freely now and returns when pressed down.

The car runs ok but starts slowly, not all of the time but often. I also think it may start slower after driving it as opposed to hone cold but I would need more data points to verify that. It just seems like it has no life. I get that this is the inline 6 and not the larger 560 V8 but I cannot imagine it is supposed to be this slow. I hope not anyhow. There simply isn;t any pickup. It almost feels like it just isn't getting enough juice when the pedal is full down.
Be EXTREMELY careful spraying anything into plenum as it may quite literally explode, especially when the engine is running. All the stuff you sprayed by now is either evaporated or burnt off, but going forward please be mindful.

The car runs ok but starts slowly, not all of the time but often. I also think it may start slower after driving it as opposed to hone cold but I would need more data points to verify that. It just seems like it has no life. I get that this is the inline 6 and not the larger 560 V8 but I cannot imagine it is supposed to be this slow. I hope not anyhow. There simply isn;t any pickup. It almost feels like it just isn't getting enough juice when the pedal is full down.
It would be useful if you could record a clip, post on YouTube and share a link - it's easier to review such issues remotely. What happens when you press the accelerator, do revs go up but no pick up in speed? Or is the car stumbling as it was about to die? Have you done any other checks (ignition leads, spark plugs, vacuum) already?

Part of classic car experience is getting intimate with your car, especially if you plan long term ownership - old school mechanics retire and in 10-20 years' time there will be even fewer available who will be able to navigate those cars. Where you are today is where I was a few years ago, too - so fear not as stuff can be learnt and this forum is a great knowledge sharing forum. With that being said I'd encourage you to start reviewing the Encyclopaedia Germanica here https://www.benzworld.org/threads/the-encyclopaedia-germanica-volume-107-aka-egv107.1450550/ .
 

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What year is it. Are you in the US? If so how was it Federalized? O2 Sensor, Cat, Frequency valve?
 

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Discussion Starter #6
1985. It does have a cat and a A.I.R. pump installed. Not sure what a frequency valve is. This is all new to me!
 

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What Rowdie said.

Once we know the federalization "level" the next thing I would look at are fuel pressure levels. Our lovely forum Canadian nobby has a 280sl andI know he mentioned his had issues with the warm up regulator.

In short , the warm up regulator is an automatic choke that gradually leans as the engine warms up.

On your car, he lives in a really inconvenient spot that I think is only accessible underneath the engine.

Paging Dr. @nobby
 

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If it runs reasonably well but is very low on power, you may have a plugged catalytic converter.
My shop inherited a basket case M110 engine job because another shop said it needed an overhaul because of low power. The owner of the car and the shop owner had a falling out so she towed it to us and we began work. Once we assembled the engine with new rings, bearings, etc. it started and ran smoothly but still had no power. We dropped the exhaust and it went like a Euro M110 should go. A new catalytic converter solved the issue.
The most expensive case of misdiagnosis I ever saw!


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Frequency/timing valve is part of the emissions system. I looked at your first pic and I don't see one. This is one on a federalized '84 280SL
100_1624 1.jpg
 

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Discussion Starter #10
I don鈥檛 see that but it does have what appears to be an A.I.R. Pump next to the compressor.
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Discussion Starter #11
What happens when you press the accelerator, do revs go up but no pick up in speed? Or is the car stumbling as it was about to die? Have you done any other checks (ignition leads, spark plugs, vacuum) already?
[/QUOTE]

Nothing really happens when you floor it. Rpms rise but not fast. If it鈥檚 in neutral the engine revs higher and easier but still probably not as high as I鈥檇 guess it would.

I鈥檓 thinking of running by a muffler shop and having them poke around to see if the catalytic converter may be bad.

Unfortunately I think I鈥檓 capable but don鈥檛 know how to check the ignition leads or the vacuum. I鈥檓 reading all I can and have tackled all sorts of things before but I haven鈥檛 had the need in the past to dig into even basic engine functionality. I鈥檝e fixed things, replaced things, re-wired things but not a lot in cars other than mechanical items. I can follow instructions well though and love learning...
 

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What happens when you press the accelerator, do revs go up but no pick up in speed? Or is the car stumbling as it was about to die? Have you done any other checks (ignition leads, spark plugs, vacuum) already?
Nothing really happens when you floor it. Rpms rise but not fast. If it鈥檚 in neutral the engine revs higher and easier but still probably not as high as I鈥檇 guess it would.

I鈥檓 thinking of running by a muffler shop and having them poke around to see if the catalytic converter may be bad.

Unfortunately I think I鈥檓 capable but don鈥檛 know how to check the ignition leads or the vacuum. I鈥檓 reading all I can and have tackled all sorts of things before but I haven鈥檛 had the need in the past to dig into even basic engine functionality. I鈥檝e fixed things, replaced things, re-wired things but not a lot in cars other than mechanical items. I can follow instructions well though and love learning...
[/QUOTE]
What state do you live in? Do you NEED all that federalization garbage?
If not...take it ALL off. AIR pump, Cat, frequency valve....probably some sort of mickey mouse fuel management box under the dash somewhere.
See what's what after that.
THEN.....standard mechanical check up.
Sparkplugs...good? The correct ones?? Wires...good? Correct?
Cap, rotor, FUEL FILTER, tank strainer....and that stock air filter....look at it. LOOK AT IT!
It's the dumbest design. I put a K&N filter on the intake snorkel....did away with the OEM air filter box. In fact I sold it to someone for $150.
 

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Discussion Starter #13
I鈥檓 hoping for decent news after taking it to an Indy I trust. Will see what he says tomorrow.

Really regretting this purchase at the moment but I suppose all I can do is move forward. I posted some pics asking what that AIR pump was and now wish I knew more about what that actually meant. Was not aware that it included anything more than that pump but it appears from searching 鈥渇ederalization鈥 that it was a pretty big deal. So some more questions-

The car is emissions exempt based on age. What all can be removed and what would need to be fixed or adjusted after? I imagine you can鈥檛 just yank things out.

You note the air filter. I agree it looks like a horrible design. How do you get a K&N on there and ditch the original cage? This will be down the road as I have to get the car running better before doing any more to it.
 

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Everybody who owns a 280SL loves it. So will you once you get it sorted. On my 380, if it started hard, it was the fuel accumulator. Your low power could be a lot of things such as have been mentioned. Just think: air, fuel, spark and attack each in turn. And don't forget timing. Good luck!
 

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I鈥檓 hoping for decent news after taking it to an Indy I trust. Will see what he says tomorrow.

Really regretting this purchase at the moment but I suppose all I can do is move forward. I posted some pics asking what that AIR pump was and now wish I knew more about what that actually meant. Was not aware that it included anything more than that pump but it appears from searching 鈥渇ederalization鈥 that it was a pretty big deal. So some more questions-

The car is emissions exempt based on age. What all can be removed and what would need to be fixed or adjusted after? I imagine you can鈥檛 just yank things out.

You note the air filter. I agree it looks like a horrible design. How do you get a K&N on there and ditch the original cage? This will be down the road as I have to get the car running better before doing any more to it.
 

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The engine runs fine but just no power... there aren't that many things that can cause those symptoms. It would be hard to believe (but not impossible) for spark or fuel delivery problems to cause those symptoms, so I'd look for post ignition problems. The kind that occur after the air fuel mixture explodes and the expanding gas forces the piston back down from wence it came. (Quite poetic don't you think) :)

Things I would check....
With the engine idling, pull each plug wire one at a time and check for reduced rpm. If you find any plugs that don't cause a noticeable drop in rpm there is a problem with that cylinder. It might not be your problem but it's definitely a problem. Note: This diagnostic check is not connected with your symptoms, but it is such an easy check to do that it's well worth the few minutes it will take. And a word of caution... remove the plug wire on the distributor side not the plug side, unless you like holding onto pulses of several thousand volts.

Ignition timing. A badly retarded ignition problem will cause loss of power (also can cause overheating but you made no mention of overheating).

Valve timing. Even more critical than ignition timing.

Blockage in the exhaust system. If the exhaust gas flow is badly restricted it can/will rob your engine of some or most of it's power. Ridiculously easy to check... disconnect the engine pipe and go for a ride. It will be very loud but if your low power problem is gone you have your answer.

Long shot. Transmission starting out in high gear.

And one more thing... not that I think it's your problem (because I don't), but if you have concerns that the air filter is possibly causing your problem... remove it and take a ride. You'll know right away if that was your problem.

Good luck.
 

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Hi
When I first got my car the ignition timing was way out. Meant the car really struggled to climb hills, I could not go over 40mph in 4th gear up any sort of gradient. I think this could be your problem.

If you don't have a timing light you can try and adjust it the old school way of going up a hill in third and waiting for pinging.

Also the bad timing nuked my mpg, I was getting around 10mpg (UK mpg, so about 8 US mpg) fixed that and now I get around 25 on a good run.
 

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Discussion Starter #19
Ok friends - an update.

Things are much better although probably not perfect. Believe it or not the throttle linkage was entirely jacked up. The white bushing apparently degraded like I read happens and instead of replacing correct they put a couple of pieces of fuel line on there to try and fill the gap. Sort of silly considering the proper part is not expensive. That alone would't do it but it contributed. On top of that the car simply wasn't getting full throttle when the pedal was depressed. It was probably about half throttle at max. Tony at Today's European in Houston replaced the bushing and adjusted the linkage and things are dramatically better.

I cannot believe how often it ends up being the basics. The car hasn't been run a ton in recent years so Tony suggested I fuel it up with high quality gas which I did and run it through to flush out the lines. I also put in some Techron and will see if flushing out the fuel system with some cleaner will improve even further.

Many thanks for the input. Since the car is new to me I have lots of little things I am working on or noticing so will try to keep clean threads in case the trouble shooting helps others.
 

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Ok friends - an update.

Many thanks for the input. Since the car is new to me I have lots of little things I am working on or noticing so will try to keep clean threads in case the trouble shooting helps others.
Glad to see you got it sorted out. I guess I'll have to add "disintegrated plastic throttle linkage ball" to my list of things that can cause an engine to run fine but have low power. :D
 
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