Unsporty C280 Sport!!!

[Gee82]

Hi all from a Mercedes newbie.

I recently bought a 1995 manual C280 Sport with FSH and 80,000 miles as a daily work horse.

Ever since I got it the performance has been far from impressive At first I found the intake hose from the MAF to the throttle body was loose so unmetered air would have been entering the system. I tightened this and it made a big difference but there is still something wrong.

The engine seems very sluggish and slow to rev and it hessitates and misses slightly at very low revs and between 3000 and 4000rpm but the idle is fine.

The fuel consumption is also very poor, I only got 103 miles from 5 gallons of unleaded from mainly A-road driving at between 50-60mph which is roughly 19mpg. To compare I averaged 28mpg doing the same journey last week in my 350bhp Toyota Supra 3ltr Twin Turbo!

I have changed the spark plugs and air filter and carried out a oil and filter change on the C280 but it has made no difference.

Does anyone know what could be wrong as I'm sure a 2.8ltr straight six Merc engine should be more lively than what I am experiencing at the moment.

 

[kth286]

Gee82

One of the coils may be failing.

It is a waste spark system with 3 coils feeding 6 cylinders and when one goes down it affects 2 cylinders.

Coils cost about £45 ish.

You need to get the codes read by a Merc specialist that has the appropriate reader, and go from there.

This engine does have a history of failing engine harnesses and the coils shorting out is often the first sign.

Get the codes read by an independent specialist.

Regards

 

[big x]

Disconnect the MAF connection.The car should run in the default mode.If this turns out to be better than when it's connected your MAF is KO.
These are quick cars when everything is working.

adam

 

[television]

I do not think that there is anything else other than the two faults answered.

With the coil packs the engine would run lumpy and viabrate, with the MAF the performance would be flat.

Malcolm

 

[Ian B Walker]

If one coil pack is iffy then best change all three as it wont be long before the other two start to show symptoms.

 

[Myros]

I just did all three on our C280

they only cost 66 + Vat for all three from GSF. Beware though, as there are two types and GSF managed to get me the wrong one first. Go armed with your chassis number, or better still order both types on a sale-return basis.

 

[Gee82]

Thanks for all the helpful comments people

I've just been out for a drive with the MAF disconnected and after the idle hunted around for a while the car ran a lot better and pulled smoothly through to the redline and even pulled 90mph at the top of 3rd gear!

So it looks like the MAF is fubard Is there anypoint in trying to clean it or should I just order a replacement asap?

Will there be any difference in fuel economy driving with the MAF disconnected till I fit the replacement?

Thanks again

 

[Blobcat]

You could try cleaning it first as that is a cheap option, Parrot of Doom has an excellent guide on the forum. However I think it is probably dead.

 

[kiwi_bloke]

wiring loom

Forgive me for stating the obvious.

These cars had a wiring loom fault which will give all sorts problems. I would suggest checking the state of this.

 

[Gee82]

After driving about with the faulty MAS disconnected for a week and the car running better I have just fitted a brand new replacement MAS.

The car now runs smoother but idles very lumpy as if its missing and backfiring and the car cuts out when I stop at junctions. The car will also only rev to 5000rpm and then stops as if it's hit the rev limiter.

I've checked the wiring loom and it looks fine and in original condition.

Does anyone have any suggextions as to what could be my problem now?

 

[jberks]

As the replacement MAS has made some difference, it's reasonable to assume the MAS had gone. As I understand it, it's quite common for a duff MAS to take out the O2 (Lamda)sensors if left for long enough.
However, the fault you describe could also be the cat breaking up.
Best get it looked at and checked out on a diagnostic or you could be chasing possible causes forever.