I own a '96 C280 with 120k miles and have recently been having a problem with the engine. Intermittently, the engine:
1) revs the RPM's while at a complete stop; or
2) cuts out momentarily during acceleration or at speed.
I've been searching the forum posts for the last several weeks and the general diagnosis for this type of problem is that it's the Engine Wiring Harness, Coil Packs, or MAF.
Since it appears to be the most common issue, I started with the Engine Wiring Harness. But, after checking the exposed sections of my harness it appears to be in pretty good shape (unlike the rotting/cracking pictures in other posts). I bought the car from a MB dealer in '98 with 30k miles on it, so the dealer may have already replaced the original faulty harness.
Second, I replaced the spark plugs and cleaned the coils and MAF. Although this gave the car more pep, it doesn't appear to have cured the problem. Plus, I don't think it's a shorted coil pack since the car has a pretty smooth idle generally (other than problem #1).
I haven't been able to run a OBDII diagnostic test yet (not that those codes ever do me much good), but the only visually obvious engine issue is a leaky head gasket (leaking in the very front of the engine). Is it possible that the oil from the leaky head gasket is interfering with an electrical sensor (injectors or air)? Before changing the spark plugs I cleaned and degreased the engine so its pretty clean now but still has the same issues.
Please help. I'm fairly new to the DIY game, but can't fathom taking the car to the dealer where they'll charge me more than the car is worth.
Vehicle: 1998 c230 non-compressor 98k at this time, a spring chicken :)
Location: central ohio
Posts: 186
Then engine is sucking outside air
Quote:
Originally Posted by sideshow76
I own a '96 C280 with 120k miles and have recently been having a problem with the engine. Intermittently, the engine:
1) revs the RPM's while at a complete stop; or
2) cuts out momentarily during acceleration or at speed.
I've been searching the forum posts for the last several weeks and the general diagnosis for this type of problem is that it's the Engine Wiring Harness, Coil Packs, or MAF.
Since it appears to be the most common issue, I started with the Engine Wiring Harness. But, after checking the exposed sections of my harness it appears to be in pretty good shape (unlike the rotting/cracking pictures in other posts). I bought the car from a MB dealer in '98 with 30k miles on it, so the dealer may have already replaced the original faulty harness.
Second, I replaced the spark plugs and cleaned the coils and MAF. Although this gave the car more pep, it doesn't appear to have cured the problem. Plus, I don't think it's a shorted coil pack since the car has a pretty smooth idle generally (other than problem #1).
I haven't been able to run a OBDII diagnostic test yet (not that those codes ever do me much good), but the only visually obvious engine issue is a leaky head gasket (leaking in the very front of the engine). Is it possible that the oil from the leaky head gasket is interfering with an electrical sensor (injectors or air)? Before changing the spark plugs I cleaned and degreased the engine so its pretty clean now but still has the same issues.
Please help. I'm fairly new to the DIY game, but can't fathom taking the car to the dealer where they'll charge me more than the car is worth.
Thanks!!
I think you answered your question in the second to last paragraph. The symptoms you described point to the head gasket failure. I doubt your sensors have anything to do with the issue. Your right about the obd for the most part although sometimes its a good starting point if there is a mil light on the dash.
Some people have tried a liquid head gasket seal with some luck but I am a bit skeptical myself of those products. If there is a head gasket failure it can cause several different problems. Have you had a chance to look at the radiator fluid for oil? If you have oil there then its time for a head gasket.
I would have a local mechanic do a compression test on the cylinders to verify before taking anymore action. B
Sounds like you've done some research, good man Sideshow! You need to know that most of the time cleaning the MAF does not work. MAF's also will cause false codes from other components while not showing a code when they are bad, like ours did... Ours was causing crazy symtoms making the car barlely run, stall, and then start working again. The MAF is one component that is a good investment if your car has over 100K and it has never been replaced. It's not a matter of will it fail it's when. This dude will leave you at the side of the road doing this
The MAF secret that periodically gets passed on here is to buy the insert only! You'll save big bucks and spend only a few (about 175.00) Some people have paid over $1,000.00 at the Stealer's. The Indy we took our car to wanted $750.00. We found one for about $285.00 (Whole Part) This was before I knew about the Insert or I'd have saved another C note.
All that wind to say you've probably just got a bad MAF.
Update: Following some advice, I changed the fuel pump relay ($25 @ autohausaz.com). This appears to have solved my initial two problems mentioned above (i.e. revs the RPM's while at a complete stop; or cuts out during acceleration or at speed), but now the car is suffering from two new issues:
1) Immediately after starting car RPM's fluctuate up and down (is "hunting" the correct term?). No roughness to it, just constant fluctuation between 500 and 1,500 RPM. Upon shifting out of "Park" this goes away, but returns upon next ignition start.
2) Upon heavy acceleration (usually from a complete stop) the engine will hesitate (maybe rumble a little) then kick in. No hesitation at normal throttle while moving.
I researched these issues and thought it may be the Overload Protection Relay so I replaced it ($58 @ autohausaz), which doesn't appear to have helped. I finally pulled the codes which revealed P0301 (misfire cyl. 1) and P0101 (MAF discrepancy). I'm hesitant to include the codes on this posting because I don't know how old they may be and I'd prefer advice based primarily off of the symptoms rather than codes (FYI... per previous post I did clean the MAF and cjshade is probably right that replacement may be needed. I just want the big bucks repair to be my last resort).
Thanks again for your help! All of your advice is very much appreciated and I feel that I've already learned a ton from y'all about DYI car repair. Please let me know if you have any ideas on the new issues.
Have you tried moving the coil on plug one to another position and seeing if the trouble code moves to that cylinder? How are your sparkplug wires? If they are original, they could be going bad from age.
You may be chasing multiple issues. Make sure your EGR valve/system plus its tubing isn't clogged up with gunk from age.
Listen to your car on this one, your lucky to get a MAF code! MAF's will go in and out and drive you as crazy as Bart Simpson on a bad day. I'll bet your money that most of your problems go away if you change the MAF for a new one. MAF's are Blameshifters and they often cause OTHER codes that are FALSE.
AutohausAZ.com seems to have the best prices for a quality part. Some people have had problems with the e-bays sellers units.
IF your problems are VERY consistant you might try driving the car with the MAF unplugged. The car will run in default mode. If it runs better without than with, then you KNOW the MAF is bad. Not a for sure test in some instances.
sideshow76 ...........got the same car as yours...........had the same "cuts out momentarily during acceleration or at speed"........in my car, flooring it would cause a compression from accelerator actuator against the L5 wire.......detuning different sequence pistons the way it was suppose to be........this was a tiny piece of wire that you got to consider reviewing it, even going through the computer to check it, or get someone with patience to go section by section until you got the problem down, it could take weeks of work, mine was the L5 piece.
I had this issue with my car. After many hours of trouble shooting, I discovered a current leak from one of the coils. How to check for this:
1) Leave the coil/spark cover off
2) Start the car
3) Remove one plug wire at a time and observe any difference in the engines behaviour
4) If you notice no change in the engines behaviour with plug wire removed, shut off engine and remove respective coil.
5) Under VERY good lighting, inspect coil to see if there are any "white/grey" spot or spots. If so, your problem has been found.
BTW, this fault didn't register on my Snap-on scanner, so it's a tricky one!
Thanks for the advice. I don't have a lot of experience diagnosing wires and voltage. What is he L5 wire, is it part of the wiring harness or throttle actuator? Were is it located and what is the best method of checking it and replacing it?
Remedy: After changing the fuel pump relay, overload protection relay, and fuel filter, to no avail, I finally got a new MAF. Replacing my MAF fixed the "hunting" idle and delayed acceleration issues. Work Time: 5 minutes; Cost: $184.37... Yippee!!
Special Thanks to all who contributed to help me diagnose the problem!
'96 C280 Engine Issues (idle,throttle,acceleration). Help!! 
I'll bet your money that most of your problems go away if you change the MAF for a new one. MAF's are Blameshifters and they often cause OTHER codes that are FALSE.
Linear Mode
