I have apparently identified a problem with the engine of my 1994 Mercedes Benz C-280: the fuel injection control. (This has caused the engine to die shortly after starting, and lack pep when I accelerate around a turn from a complete stop.) On the advice of a mechanic I know, I removed the paper filter from the air cleaner; the engine runs better.) I want to know: Is this adjustment complicated or expensive (or both)?
What exactly do you mean by “fuel injection control?”
Does it die shortly after starting with a cold engine, a warm engine, or both?
Does it really lack pep accelerating from a stop around a turn but not going straight?
Normally it’s not possible to discern a performance difference between having a non-clogged air filter installed and having no air filter. Was the old air filter quite dirty? In what way does it run better without the filter?
Just what adjustment are you talking about? (And don’t say “fuel injection control adjustment” – that’s meaningless to me.)
You don’t have a maintenance free late model Japanese car, you have an old German car. It needs special attention.
Find another 20+ year old Mercedes and ask its owner where they take it. You’re probably looking for an independent shop owned by a former Mercedes dealership technician. The hourly rate will be fairly high but they’ll actually know how to fix your car instead of giving you bad advice to get rid of you.
To clarify: There is a large rubber tube that runs across the engine block–the block’s top is even indented to accommodate it. Its right-hand end connects with a vertical piece just to the right of the block (as seen from your point of view when viewing the engine when standing in front of the car with the hood up); its left end joins with another piece at top left, just to the left of the engine block. The entire tube sequence ends at lower left, where the air cleaner is. Also at the right-hand end is a sensor, attached much like a bottle top to the tube and connected with a wire to an engine part I can’t see. The piece of tubing is called “Motronic air mass sensor intake pipe.” The connections at both ends are circular metal bands, tightened or loosened with a screw fitting.
I figured there is apparently some central gadget that controls the fuel intake to each of the six cylinders (which use fuel injectors), and apparently this is what needs adjustment.
Apparently you are describing the mass airflow sensor and the air intake tube between it and the throttle body. This sensor is a key component in the fuel injection system. If there are any air leaks in the tubing between the sensor and the throttle body then engine performance will suffer.
These are hose clamps. They should be tight enough to hold the rubber duct securely to the metal ductwork.
Said “gadget” is the engine control module (ECM), commonly called the computer. It is not adjustable. Problems in this area are commonly caused by faulty sensors, air/vacuum leaks, or poor electrical connections. There are many other components that can give trouble: the fuel pump, fuel filter, fuel injectors, various ignition items, etc. It’s pretty hard to sort these out over the internet. What’s going to fix it is not some adjustment, but proper testing to identify the cause(s) of poor performance.
And to answer this: the testing and repair (not adjustment, which does not apply) isn’t always difficult or expensive, but it certainly can be. It depends on what in particular is causing the problem.
It’s easy to go through a lot of money guessing wrong about what repair is needed. As Emtar suggests, the most efficient path is to engage a competent mechanic experienced in Mercedes repair.
Ay, there’s the rub.
I’m getting a clue here on “I removed the paper filter from the air cleaner; the engine runs better.”
This suggests to me a major tune-up is in order; replace everything that needs to be replaced regularly; filters, plug wires, PCV valve, coolant, everything the owner’s manual says to do. Hire a competent mechanic and just pay the price, count it as the price you’re willing to pay to drive a 1994 C-280. In return everyone will think you a person with excessive disposable income because C-280’s are great places to dispose of your income. Jaguar XJ12’s are and even better place to dispose of your income.
It might be cheaper to make monthly payments on a new Ford Focus or something …
If it looks to you like you could access the air intake (the tube with the hose clamps) on your own and take it off or just apart and get to the place where the MAF sensor plugs in, then you can try to clean the MAF sensor. The hose system probably separates near the MAF allowing access.
The MAF will be a couple of wires with maybe a screen in front inside the tube where the sensor plugs in. If there is a screen it may be plugged with debris like leaves or something. Something that may have bypassed your air filter. This is why you do not want to keep driving with your air filter removed.
Any auto parts store will sell you a spray can of MAF cleaner and you blow any debris away from the screen with the spray and spray the wires to clean. Of course you will leave the power off and disconnect the MAF plug in. Oh, and DO NOT TOUCH the MAF wires with anything other than the spray.
If you do not feel very confidant in doing this, then follow the other instructions above to see a qualified mechanic. Your initial description in the OP leads me to **strongly recommend the mechanic. **
A dirty MAF sensor or plugged screen may or may not be your problem but it is the place I would look first since your performance improved when you removed the air filter, that says restricted air flow to me.
For me personally I consider cleaning the MAF sensor to be routine maintenance, but my car has it’s own man cave. You will have to determine if your own time, place and skill set makes DIY a good idea.
And it may not be the problem at all. But it is a good first place to look.
Just want to endorse Dallas Jones post which is exactly (and more comprehensively) what I would suggest.
I have gingerly cleaned a Mass Air Sensor using spray carb cleaner and a cotton bud. It worked but only briefly. We’d been told the car needed a new ECM and so it proved to be.
You can also spray carb cleaner into the throttle body to clean out fuel deposits. Simple enough and worth trying.
It is probably not a hot wire type sensor found on modern engines. Bosch fuel injections from that era had an actual moving vane type sensor. On the mechanical fuel injections (Jetronic, I had a Jetta with a K Jetronic)) , it directly opened the fuel metering valves. On the electronic system (Motronic) it sends a varying signal to the metering valves. It is adjustable, under the cover. You need to know what you are doing however.
There are some YouTube videos addressing the issues, but I haven’t viewed them to see how easy this is to do for an amateur.
Dennis
You’re a little off on your timeframe. This vehicle has a hot film type sensor, not a moving vane type. There is no adjustment.
If it’s a 1994 model then any of the sensors such as an oxygen sensor could fail. Those sensors are 22 years old.
If a computer doesn’t receive all the normal inputs then it has to either shut down completely or calculate fuel flow based on the remaining sensors. The result is going to be a richer mixture to accommodate the unknown so the engine can keep running.
Thanks. I was a BMW driver back then. Looks like the E34 (5 series) had the true mass flow sensor up to 1993 and the hot wire starting in 1994 also.
Dennis
The friend (a former neighbor who had sold us the car I drove before the Mercedes) and I apparently discovered the problem. The crosswise air tube does figure in it, however obliquely.
I had mentioned a vertical tube rising from the port side (though on one’s right if one is viewing the engine from in front of the car) to which the crosswise tube is connected with a hose clamp. I had noticed that the hose did not “seat” very well on this vertical connection, regardless of how we were tightening the hose clamp.
The vertical tube, it turned out, had a flange that the hose clamp was to fit over; the crosswise tube was not the culprit at all. The flange had broken altogether from the end of the vertical tube, as I confirmed by matching the broken surfaces. (It was hardened rubber.) We got one of those high-powered glues, glued the broken surfaces together, waited 30 minutes, and retightened the hose clamp, refastening the vertical and crosswise tubes together. When we were satisfied that everything was reconnected, I started the engine–and it roared into power. I test-drove it, running it back and forth twice through the mobile-home park (202 spaces) where I live. So far, so good.
That sounds like the intake air heater… it takes air off the exhaust manifold to warm up the intake air.
This might be the only fix required if the problem is only ever in the first minute while the engine is cold.
I think the removal of the air filter was simply testing to see if it needed a clean air filter… You seem to suggest it ran better without a filter, which obviously means it needs a new filter.
No, not on this particular car. Best I can tell, it was part of the ducting between the airflow sensor and the throttle body.
Just how much of the engine volume (size) is taken up by the throttle body?
This will give you an idea.
That’s it?? Is that part deep in the innards of the engine? From what some people have told me, the throttle body is a critical engine component and repairs can cost around $500.00! :eek: