berettagtz

I just came back from a long trip and my C240 started acting up. The check engine light came on and when the car is stopped there is some slight shaking. It accelerates really slow, not like before... I was thinking it might be the spark plugs or the wires maybe?? If anyone has any ideas, please help!! My nearest dealer is about 200 miles away, so I kinda need to see if it is something simple or if I should take it to the dealer.
Has anyone here had the same problem??

Thanks in advance!
ps.
I have a confession: Prior to the trip I didn't put the premium fuel in my benz! Could this be the problem??

berettagtz

I put some techron and filled it up with premium today. How long does it take for techron to take affect?

LuxuryC240

It could be the fuel, as long as you have normally used the premium, hopefully that was it..but from what I've read using the regular fuel by accident does not damage the car, but on your long trip the effects may have heightened or whatever, im not sure what techron is so im not sure on that...good luck, and let us know if all turns out ok

Mu9enx

putting less than premium fuel into my car caused it to sputter when i hit high rpms and it accellerated pretty slow also. that just might be your problem

e1000

if the engine light is on, it's more than just using non-premium gas, take her in

KIRA

try add some Octane boaster

spyderpig

Or you can give me that money insted... the car's gonna end up at the stealer anyways. lol.

berettagtz

I checked the codes and it has missfire on 4 cylinders!! It almost seems as if the car works on fewer than six cylinders! It sputters a lot, and it is really slow to start! I bought some spark plugs. I'll see if that will help any! But I am afraid that this is more than just the sparks! I hope it's not!

caliboi1234

My C240 started doing the same thing went to the dealer....

had the fuel pump replace....

about an 1 1/2 and $300 later

she was as good as new

berettagtz

Caliboi!!!,

did yours have the same codes (missfire)??

bensitto

Mass Airflow Sensor! Unplug the MAF then drive it, if it runs okay with it off that's your prob. If so you can disconnect the MAF and clean it using CRC MAF Cleaner. I had the exact same symptoms you desribed on my ML. This fixed the problem. You need to use a torx security bit to remove it.

Good luck!

berettagtz

thanks bensitto and all!!

I will try to clean the MAF.
How hard is it to get to it? Anyone know?

bensitto

first disconnect the plug going to the MAF and try driving it. If it's driving good again that's your prob. Not hard to disconnect at all. But like I said you need to get a security torx set. Forgot what size exactly but do a search for MAF removal and you'll find details.

Good luck!

eddymoussi

Do you know any good site that sell MAFs?

I have a C230 03 coupe.

damaged

Your problem sounds more like a plugged cat or a sticking EGR valve.
The EGR valve only opens on decel, and if it does not snap shut it will cause the engine to idle very rough, you should not loose that much power though.
A plugged cat will cause all your symptoms, both will cause PO300-O306 missfire codes.
Airmass faults can also cause misfire codes, but be careful in your diagnosis.
Cleaning it can cause more damage. Rebuild units are now available for about $200.00

berettagtz

I tried unplugging the connector, but had no luck. It's hard to get my fingers in and pull on it at the same time.
I bought a set of torx security bits but they are the wrong ones. I think the ones I need are 5 stars, and the one I bought were 6, so that didn't work.
Is it possible to unplug the connector without having to take the two torx screws out??

I will try to eliminate possible solutions one by one, so right now I am going to stick to checking the MAF. If that doesn't fix it, I will consider one of your others suggested solutions!
This seems like a common problem in C class, so I will keep everybody posted on my progress!
Thanks for all your responses!

eddymoussi

I have unplugged the MAF in my car, and it seems that the car is behaving better. Except that CEL came on, but that's not an issue it will go away in a day or two.

I am searching now for the best price of a MAF.

berettagtz

I unplugged the MAF and had no luck!!! I really hoped that this would be the MAF, but I guess not!

When I unplugged it, it almost seemed as if the problem got worse... Maybe it was just me, but it sure didn't help it.

Any other possible causes for this problem?

damaged

See my earlier post !

berettagtz

so how do I deal with a plugged cat? Do I replace it?
It's gonna cost a lot of money if it's the cat!

damaged

Yes it has to be replaced, but it is covered by emission warrenty in the US until 80k miles or 8 years.
But you need to get it diagnosed correctly first.

C230 Sport Coup

If you buy one from the dealer.
I got a Magnaflow cat recently for 300 installled.
MBZ price for the part was 1500.

But like someone said, maybe a warranty item.
Look around the exhaust pipe.
See any grey dust?

Mine was spewing it in the end....

How many miles on your car?

As far as premium goes, I've had many loaners, and the normally aspirated engines run fine on lower octane.
My car only had 87 octane once, and it ran with the timing very retarded, but no CEL's.

berettagtz

My car has 96,000 miles on it.
Will the cat be covered under warranty even though it has over 80,000 miles on it and is under 8 years old??
BTW, I think the regular MB warranty expired!!

The symptoms of the car are: when at idle the car vibrates, and when I step on the gas pedal, the engine sounds like it's "choking", and my biggest problem is that it lost power - probably by half as much.

The codes read missfire on cylinders 1,2,5, and 6.

thanks for all your replies!

berettagtz

I just talked to stealership, and they said that the cat would cost me 900-1100 dollars!!

berettagtz

just replaced the spark plugs on cylinders 1, and 2... spark plugs looked pretty bad, but it didn't seem to fix anything!!
I am taking the benz to one of the local shops, and I will see what they tell me tomorrow... I am keeping my fingers crossed, but at this time I don't think it will be anything cheap!