leviohanenye

Hi, I have a 94 C280. I cleaned the MAF sensor and the rough idle with and without the A/C on has gone away. The only thing that is still lingering is my misfire. What is going on and what could be causing it? I'm not that mechanically inclined and I don't have too many tools, but I'd like to get some type of idea.

leviohanenye

I noticed that the air intake (the small little hard plastic thingamabob that sucks in air) that connects to the bottom of the air filter box keeps coming off, and I think thats reducing the amount of air that goes into the engine. Do you think that that could be causing the MISS. I'm going to a shop hopefully today, but I don't want to get ripped off (College Student). We don't know much about the car. This is the only service history that we have (plus the maintenance booklet is stamped until 112,000 miles. My question is based on the previous service history, what do you think needs to be replaced now? The car is at 173,500 miles. 02/02/2009 148,966 Mercedes-Benz of South Atlanta
Recommended maintenance performed
Maintenance inspection completed
Valve cover gasket(s) replaced

10/30/2008 146,657 Georgia
Passed emissions inspection

10/18/2008 146,459 Mercedes-Benz of South Atlanta
Camshaft position sensor replaced

08/14/2008 144,313 Mercedes-Benz of South Atlanta
Maintenance inspection completed

06/19/2008 142,677 Mercedes-Benz of South Atlanta
Engine idle/timing adjusted
Oil and filter changed

03/20/2008 139,872 Mercedes-Benz of South Atlanta
Transmission oil pump seal replaced

ptcruiser

explain the misfire in the best way possible.

leviohanenye

Its like when i'm driving, and hit the gas suddenly, or need to pass someone itll start misfiring like back to back to back then itll smooth itself out, and itll do that for a while. I noticed today that the rough idle problem is back also .

leviohanenye

Also, I called the AutoShop, they said that since 2012, the rear brakes, one of the oxygen sensors, the fuel filter, the oil main sending unit, and the rear main oil seal have all been replaced. I know it is due for an oil change also.

ptcruiser

From what your saying, it could be the air/fuel mixture, and possibly the ignition plug coils breaking down and spark plugs. How did you clean the MAF? Did you use a specific product like CRC MAF cleaner? Did you take the MAF tube off to clean it?
The other thing is the throttle body may have some blockage at the side vent.
Easiest place to start is spark plugs, next is the throttle body, and the ignition coils would need a shop test to confirm. To do the plugs and throttle body is about an hours works for both. You will need some specific tools (sockets).
There are some youtube videos that will walk you through the plugs and the throttle body. Be sure to buy some Seafoam to clean the throttle body. Most places like NAPA etc have it but be sure to tell them what your using it for, as they have several products.
That should solve the problems I would think. Time to get your hands dirty and become a DIY kind of person. Every thing is easy with common sense and taking your time, and don't rip and tear. Be a gentle lover :-)

leviohanenye

Thanks, but I don't have many tools. I did use CRC Cleaner and where is the side vent located?

cm60k

Many things could cause this, but I prefer to diagnose the car to see if any code appears..!

ZAYED,,

ptcruiser

Well, as Zayed mentioned, a full diagnosis is always the best way to pinpoint a problem. An OBD 2 can work to get the codes, but the Mercedes Star system is the best. Is the check engine light on?
To get back to your question, look at the Youtube video about cleaning the throttle body,
You will see how it's removed, and there are 3 things to remove, before removing the throttle body from the manifold.
1. the air intake tube that runs from the air cleaner box to the throttle body.
2. the electrical connector on the left side (be gentle so you don't break the clips).
3. The small rubber tube on the right side of the throttle body.
If you don't have the tools, maybe take it to a shop that does, but maybe some friends will have what you need. A lot cheaper.
Note to Zayed: Got the mirror in, and it works just fine......

leviohanenye

Today has been crazy. The CEL went off, but not for the right reason. I washed the car but left the light on, so the battery died and the car reset, so theres no CEL. Does the lack of a CEL mean no codes when they're read, and how long will it take for the light to come back on? a link to the vid containing the miss, it happens around 2000 rpms.

ptcruiser

The check engine light comes on when something requires attention. If it is off, then there is nothing to be checked, but not necessarily.
Good idea to get a read out to see if anything is hiding in the woodwork.
How did you get to the battery if it was flat? I assume you have a Valet trunk key to do it?

ptcruiser

Your video is not overly clear in the sound department.
I did here what sounded like a popping noise.
You may want to get a compression test

leviohanenye

I thinks its a misfire and sorry, it was filmed from my phone. I'm saying if I take it to the mechanic since the battery was dead how can they tell whats wrong without me driving it. If I drive it im risking making it worse. And the key still worked manually, I just pushed it in.

leviohanenye

The misfire starts around 7 seconds. I dont want to drive the car with the misfire to try to get the code back because I dont want anything else to happen to my car.

leviohanenye

I do have the tools that came with the car if that helps lol

ptcruiser

Your not going to hurt anything. Do you have jumper cables?
If you do, just jump it and charge it up. These cars do not explode :-)
Be sure it's positive to positive and negative to negative.
I believe the positive is the battery post closest to the back seat area.
FYI, on batteries, the biggest diameter post is always positive.
The lol is understood... No, the tools that came with the car won't work.
If you watch this video, the guy tell you what you tools you need for the throttle body.

leviohanenye

No no no ive already jumped started the car but that reset the CEL. Thats why im wondering if they can still look up the code.

ptcruiser

Yes, they certainly can.
The engine scanner will pick up any and all codes, even though they don't show on the check engine light.
If you want, here is the link to what the engine codes mean. A lot of it won't make sense to the layman, but it's worth having.
All the codes mean the same for all vehicles on the road in the US.
This includes imports that have to meet US safety and emission standards, and Mercedes is one of them.
This is just a write up explaining the CEL
http://www.samarins.com/diagnose/checkengine.html
These are the codes you may find with a proper scan. Scroll down to see them all.
http://www.obd-codes.com/trouble_codes/
As you may note, some outlets like Auto Zone will do the scan for nothing.
It's a sales tool, but it's free and no obligation.
The absolute best scanning device is the Mercedes Star system.
If you can find a shop that does Mercedes work, and has this scanner, I would recommend using them if the price is reasonable. It takes about 15 to 20 minutes to go over everything.
You are safe to drive the car.

leviohanenye

I just didnt want to drive all the way to a shop, and find out that the light not come on and the mechanics not be able to do a full diagnosis. Also, the local shops that I've called are quoting 5-600 dollars to do a full tune up (plugs, coils, wires). Is that reasonable? How much will i save by doing it myself?

ptcruiser

As I said, don't worry if the CEL is not on. A scan will tell you what's up.
Plugs on Ebay are $22.00 for 4. I got 4 for about $5.50 each which is equal. Bosch plugs FR8KTC. Clean throttle body with Seafoam about $12.00 a spray can.
Diagnostic if you use Auto Zone for example FREE. Plug wires on Ebay about $60.00
Total $94.00. You will need a few tools, but you should be able to borrow a ratchet (3/8 drive is best) and an extension. Flat head screw driver, a spark plug socket, and 2 sockets which are available at any parts store. You need them to remove the panel covering the plugs to get access, and to remove the throttle body. Total cost for those should be $8.00 to $12.00. Now you have about $106.00 invested, and about 2 hours work. You do the math and the answer is obvious.......

leviohanenye

Spark Plug




Spark Plug




Dirty Wire




Spark Plug




Coil




Coil




Coil

I have a question though. Does the oil on the plug mean something bad? Also, do i need a special tool to take off the plug? I read somewhere that some type of grease has to be applied to the spark plug before it is reinstalled is that true? How do I get the igniton coil off? In addition, people have said something about having the correct amount of torque on the spark plug. How do I do this? Does the ignition wire need replacing? Finnaly, how do I remove that stupid ignition coil? Thanks

ptcruiser

First question...The oil on the plug. Do you mean on the outside of the plug before it is removed, looking down the tube where the plug is? If that is what you mean, no big deal.
As far as torque is concerned, without a torque wrench, you do the following. With the plug socket (preferably a plug socket with a rubber ring inside so it holds the plug in the socket), you screw in the new plug gently until it hits bottom. One it has bottomed out, tighten no more than 45 to 60 degrees with the ratchet. Over tightening is a no no, but some people want to torque to until their wrists break. It can strip the plug threads. and then your screwed, literally. Don't apply anything to the plug threads.
The ignition coils are (2 of them) as shown in your attached coil photos, are removed by undoing 2 screws each that hold them in place. They sit right over 2 of the plugs (a black square thing as in the photos) Once that is done, you simply pull up gently, and the plug wires will pull off the plugs. The rear plug closest car has a small rubber that guides a cable to the area where the plugs are located. Just pull this up so the wires are loose and easier to remove. When I say remove, i mean remove from the plugs, not the car. You will see it as you proceed. Sometimes they seem hard to pull off, so gently twist them left and right about 20 degrees each way, and pull straight up.
Once removed. you will see the plugs in the tube. Then use the plug socket and remove them. Do you need new wires? That all depends. If the old ones are hard and brittle and possibly have some fine cracks in the black rubber, then replace them. If not, then don't. FYI, the ignition coils (the 2 of them are quite intelligent, and don't say much, but you can carry on a good conversation with them if you want :-)

rick hesek

Have you performed a compression check? Do this before you start spending money on parts.
All the cylinders should all be within 5% and up to factory spec.

Rick H

leviohanenye

Okay lol and what is the dielectic grease? Do I really need this?

ptcruiser

No, you don't need it. It is a grease designed for electrical connections. I use it on things like electrical plug connectors that may be prone to moisture, like my motorcycle.
As mentioned by Rick, a compression check can tell you a lot. As I mentioned earlier, if the valves are bad, it will show, but it will also show if you find a Mercedes Star diagnostic machine without using a dealer.