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Fuel Air mixture getting worse?

3K views 40 replies 8 participants last post by  Weather Man 
#1 ·
I am starting a new thread because the old one is beat to death and I wasn't getting a response.. New parts have been added so I'm starting fresh with this one.

Fuel tank was rebuilt, fuel pumps are new, filters are new, lines are clear, Fuel Dist is used and from running wreck car, Injectors all removed and cleaned and plugs are new.
Just removed all exhaust and welded up the holes and put in a new O2 sensor.. OEM cheap from Ebay. Since then, tests aren't doing the same thing, so I want to know if these results indicate the O2 sensor. I did Volt meter test to the O2 sensor and it seemed functioning fine.

On my previous tests however, I was getting correct fluctuation in volts in Pins 3 and 2 from idle to 2,500rpm:
(Old Test) Engine at Idle = 6.67 - 6.89 range and engine at 2,500 = 13.36
(New Test) Engine at Idle = 6.3 - 6.9 range and at 2,500rpm = volts drop to .29v

I performed the "Static" test on Pins 2/3 with engine off and results are:
Key on engine off = 3.5v
Plunger down throttle at idle = 10.42v
plunger return to idle = 6.99v
plunger slightly depressed = 3.55v
plunger return to rest = 6.99v
full throttle w/ plunger at rest = 9.1v

What has caused my Pins 2 and 3 Lambda reading to drop to near zero at 2,500 RPMs???
Is this signs of the O2 sensor or something else??
The vacuum guage will not peg left at idle..

Attached video shows the current symptoms... Thanks for any help...

 
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#3 ·
"The vacuum gauge will not peg left at idle" .

That's your issue right there. You have a vacuum leak somewhere in your engine. Someone else said it but vacuum leaks on these engines are the cause of some of these problems you're facing.

Get a mityvac and start testing the lines.

There is a somewhat risky suggestion out there of using an UNLIT propane torch (gas) and letting it letting it puff out the gas around the engine bay. The theory being, any vacuum leak will pull in the gas and cause the engine to accelerate. Do this at your own risk!
 
#6 ·
From my understanding of how the system works (and someone else can chime in and correct me) the economy gauge is connected to the intake manifold where it measures the suction. At idle, you may have a vacuum leak which is being resealed at higher RPMs (more rpms = more suck) probably sealing an otherwise worn rubber bit.

At idle, your economy gauge should always peg to the left and not fluctuate. I would check along the back of the engine towards the large vacuum line going to the brake booster first.
 
#9 · (Edited)
Yes it is extra work, but with the money you've spent on this car and my own experience with vacuum my thought is why not invest the little bit in putting new vacuum lines and ends on the engine? Age and heat cycles take their toll on the ends and lines. Ends become hard, brittle and can have leaks. Lines can crack and break easily.

Think Nobby had a post where vacuum diagrams for various models were posted. Follow that for routing and the EPC for numbers needed to get the pieces you need to do the job. Most of it is sold by the metre and you cut to length. Some of the lines have been replaced by just an opaque plastic line instead of colour coded. BUT, overall, cost is cheap, takes just a little work and diagram reading and the benefit of having the vacuum working as it should be is worth it.

In my particular instance the lines were as I described above. Then, upon looking at the diagrams and finding where things were supposed to hook I found that a PO had rerouted things non factory. Car ran okay when I purchased it, but ran much better once I fixed the bad and incorrectly routed lines.


EDIT: Never mind. See your post heading on overhauling the vacuum system so guess you've been there done that
 
#11 ·
So I guess my concern is the 2 recent changes I made to the car between it running somewhat ok and now losing vacuum and not running ok...

I took the exhaust system down from manifold flange back and repaired all holes. The cats sounded like they were full of kitty litter so I know they are basically gutted. BUT, I still haven't put a muffler on the rear of the pipes yet. so the exhuast pipes go all the way to where a new exhuast would connect, just before rear tires...

Would this cause a problem with back pressure?

While I had the pipes down, I could not get the damned O2 sensor out and ended up drilling the thing out of there... I reinstalled a new OEM from Ebay O2 sensor. I tested the wires on the O2 and it seemed to check out..

Would a defective O2 sensor cause a reverse in Lambda reading??

Something since I made these 2 changes has started caused this change in Vacuum and Lambda cycle...
 
#13 ·
If your new spliced wire is good, then check to make sure the sensor is actually plugged into the fuel injection brain correctly. The plug on my 380 lives under the passenger kick panel. It's the green wire.

I'm going to bet the wire is attached correctly.

You probably just developed a new vacuum problem by jostling around the hard plastic vacuum line towards the rear of the engine. Get a mity vac and check!
 
#12 ·
At this point, age and heat wise, I have the view it is part of basic maintenance on these. Might be a minority on that, but there you go. At the very least, has been my limited experience that it is worth checking and doing.

Any rubber ends that are hard as a rock are a good indicator. Don't know how your system is on the 560, but on the 450 I have a couple of larger air hoses on the engine too and they were hard as well. Took one off and it came off in little chunks. Replacement with new AND the verification of where the hoses are going in relation to the correct vacuum diagram for your car is worth it. Really is a pretty small investment to do so.

May or may not help anything you are having an issue with now, but at least you will have piece of mind all is correct on the engine and that you don't have any seeping vacuum lines waiting to bite you later.

After I did the vacuum on my car I saw a interesting video on MB vacuum lines by Mercedes Source. Talked about all the vacuum and air hoses on MB engines and how they get brittle and how the ends stop fitting correctly. Could not find it at a glance, but this one covers the topic although for diesel, but same principals apply.



What I did when I did mine was print out the vacuum diagram info and then go to the EPC. Got the number for each hose (many are the same number) and marked the part numbers on the print out. I simply wrote the part number down on the bottom of the sheet and put a letter by the part number. Then on the actual picture on the print out I put the corresponding letter next to each hose I found was the same. I then estimated lengths for each hose with a bit extra. You'll find a number of the ends are actually bulk hose as well that you just cut a piece and place it on the end of the hard line. There are also a number of preformed curved hose ends that go on. I marked all of these and counted up how many I needed.

Once all arrived it was just a matter of working on one line at a time. Once I had a line replaced I took a highlighter and highlighted that line all the way on my vacuum diagram. That way I could keep track of what had been done and ensure that lines were run where they were supposed to be.
 
#14 ·
I've searched the car over... Engine bay, underneath around engine and trans, under the dash..

All vacuum lines look good. Boots are not rotting. I see no loose lines or connections missing a line...

I have a mitty vac, so do I check each and every line?
Or is there a central line that should hold pressure that i check??

Thanks
 
#15 ·
I gave you your first place to investigate in my previous post!

You probably just developed a new vacuum problem by jostling around the hard plastic vacuum line towards the rear of the engine. Get a mity vac and check!

Standing directly in front of your engine in the upper right hand corner of the engine bay is the brake booster and brake fluid reservoir.

Directly to the left of it is a long pipe with a plastic check valve on it. That is the pipe you need to check.



This is a picture of a random r107 engine bay. You can see the plastic check valve I am talking about peaking up behind the air filter housing.

Make sure that pipe is holding vacuum both near the manifold where you were playing around at and towards the end holds a vacuum. Your symptoms sound like there's a slight leak somewhere that seals up when significant vacuum is applied.
 
#16 ·
Once you've taken a look at that line. I would say, yes you need to check every line to ensure where this hair pin leak is forming.

Get some golf ball teas, go to this site https://www.startekinfo.com/StarTek/outside/11883/?requestedDocId=11883 , find your vehicle and its appropriate vacuum guide, and start.

Go towards the top of the system and bypass the HVAC and door lock systems. Seal off the main vacuum line. Start the car. Does the idle peg sit all the way to the left ? Yes or No? If yes, then you have a leak in either the HVAC or door lock systems, if no then the leak is somewhere up stream.

Use the instructions in the manual and go from there.

I just did some vacuum troubleshooting of my hvac system recently and believe me this is a pain to do but it's the only way to get the system functioning. Visual inspections mean jack diddly. Get in their with some tools and start troubleshooting!
 
#17 ·
Ok, I'm getting plenty of vacuum at the brake booster... But I'm getting zero vacuum on the ports I've circled in red... I sprayed some ether near them with the plugs off, and nothing reved up or changed... basically I can unplug any vacuum line and the idle isnt changing..

I will seal off the HVAC to start process of elimination..

Also in the picture, the Greena and Blue line I painted are switched at the #80 port.. that shouldnt matter should it??
 

Attachments

#36 ·
I'm not getting any vacuum at all to any of the 4 lines going in and out of those valves 79 and 80 on that diagram..

Shouldn't 2 of them have vacuum at all times? When the engine temp hits 50degC on Thermovalve 80 and 70degCelcius on Thermovalve 79 they should open up to allow the vacuum to pull through correct?
 
#32 ·
The post 17 circled item is a thermal vacuum switch. At a certain temperature value the switch is open to allow vacuum to proceed through to whatever is connected on the other end. In your circled illustration this would be vacuum from the engine through the thermal switch to the EGR valve. Conversely, the valve is also used, to close off vacuum by temperature.

You indicated that the lines were swapped at this switch. Would not think that would be an issue as the switch is basically an open and close type valve. You may as well swap them to be correct though.

On the engine side hose connection (not egr valve side), go to the actual point at which the engine side hose connects to the engine. Remove the hose from the port at the engine. Now see if you have vacuum at that port. If you do have vacuum at the port, but none at the hose end by the switch (of course when hose reconnected) then you have a faulty line to that switch leaking off your vacuum.
 
#33 ·
The post 17 circled item is a thermal vacuum switch. At a certain temperature value the switch is open to allow vacuum to proceed through to whatever is connected on the other end. In your circled illustration this would be vacuum from the engine through the thermal switch to the EGR valve. Conversely, the valve is also used, to close off vacuum by temperature.
Is there a known temperature that these ports should start drawing vacuum?? Operating Temperature?

I could use that info to check to see if they are getting vacuum... process of elimination..
 
#35 ·
Ok that makes since... so now I'm going to use the mittyvac to start testing lines...

Are there any lines that won't hold a vacuum becuase they are not supposed to? If I use the mitty vac and start pulling on all lines going away from the motor, which ones should I test and which ones should I not test??

Can I test the HVAC lines going into the cab? should those HVAC lines hold a vacuum??
 
#37 ·
Twist in the plot with FD...

Ok, so my vacuum gauge on the dash was not pegging left and the car runs but sputters when warm and revving up to higher RPMs...

So i decided to try switching out my old FD to see what would happen.. When I did, the vacuum gauge is now pegged left! The car won't rev and I know the FD is not good, but I now seem to have vacuum at idle which I did not have with my newest FD...

Is that an indication that the new/used FD I bought is the problem?? Can the FD itself cause a vacuum loss??

Thanks for any ideas...
 
#38 ·
Ok, so my vacuum gauge on the dash was not pegging left and the car runs but sputters when warm and revving up to higher RPMs...

So i decided to try switching out my old FD to see what would happen.. When I did, the vacuum gauge is now pegged left! The car won't rev and I know the FD is not good, but I now seem to have vacuum at idle which I did not have with my newest FD...

Is that an indication that the new/used FD I bought is the problem?? Can the FD itself cause a vacuum loss??

Thanks for any ideas...
Swap in a new fuel distributor and see if it solves it. Claim the new one was faulty.

Wouldn't be the first time a brand new part was faulty.
 
#40 ·
Found one major problem!

OK, so I took the FD off and found that there was no O-ring at the base, so I had an obviously massive vacuum leak. I found an O-ring that fits it nicely and replaced it. It immediately ran like a brand new car! Reved up perfect, idled perfect... Then once it warmed up after about 2mins.. It runs like crap..

As soon as the temp needle starts to move, the car starts idleing rough and spits and sputters when I rev it up... I can get it up to about 4k RPMs, but it does not like doing it...

Shall I try an Italian tune-up?? The highway is 15mins from me, but I do have a long by-pass where I could low gear it around 45mph for a while....

I soaked and cleaned all injectors and replaced all rubber boots.. New plugs are in, but I can pull them again to check.. The Fuel pumps and filter are new, but I just now changed the filter again just as a precaution. Fuel tank is refubished. My vacuum guage pegs left like it should, but it does pull right on acceleration..

My Question is, if any of these were at fault, then why aren't they at fault all the time?? What could cause this cart to go bad when warm???
 
#41 ·
When my breather system was plugged, the car would buck and balk then die. After I pulled over and released the gas cap, it would go another bound., then repeat. Get the check-valve and the 3-way at the canister. Also there is a color-coded thermo-switch beneath the air cleaner that controls the system.
 
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