98 C180 Small problems (I hope) that need advice.

[hobnob]

Hi, I've just got my first Mercedes and so I wasn't sure what to look out for when I got it. My previous car was a Mazda 121, so the sheer size difference took some getting used to alone. After a few weeks I've identified two, or maybe 3 problems and I'd love some advice.

1. Engine sometimes hesitates when accelerating. It also feels like it's lacking in power going up hills. I'm assuming this is an MAF sensor problem. I read that disconnecting it and driving would let me ascertain that for sure (will drive properly with it disconnected if it's got problems). The question: Is it ok to just disconnect the wire with the key out of the ignition, drive it and then reconnect it with the key out of the ignition again. There are no warning lights at present and it's not a particularly bad problem, but I'd like to get to the bottom of it before it gets bad.

2. Slightly noisy fan belt. It's a squeaky sound as though It needs oiling. I think this may be connected with a loud squeaking/squealing noise when I have the steering wheel fully locked (particularly in reverse). Maybe not. I'd appreciate any insight into this.

Thanks in advance.

P.s. I really wanted a Subaru, but now I don't think I'll be able to drive anything else. Just have to get used to other road users thinking I'm a ***** now! <grin>

 

[MercMania]

i had a similar proplem i just changed maf sensor and was fine since

 

[Stratman]

Number two sounds like the belt has stretched and is slipping or the automatic tensioner isn't doing its job.
The loud squealing is the belt slipping on the power steering pump drive pulley. It does it when it's being held on full lock because you're asking the pump to turn the wheels further against a hard stop and the pump is applying maximum power trying to do this, more power than the loose belt can apply via its friction drive on the pulley.

 

[hobnob]

Thanks to both of you. Going to unplug the MAF sensor tomorrow and go for a little spin to see if that sorts it, and if it does I'll clean it, and if that doesn't work I'll replace it.

How should I go about checking if the belt tensioner is working properly? And is it something that I'll be able to do myself?

 

[grober]

The belt sometimes stretches as been said-- they are a cheap replacement from EUROCARPARTS normally Contitech [OEM for Merc] Note there are usually 2 sizes one with air con [ longer] one without. The tensioners don't often go wrong [ internal spring] but the pulley bearings go or the small anti vibration damper bushes wear out.There is no real effective "test" other than substitution or trying the belt tension manually. this post might give you idea of the layout of the belt How to do a water pump - 1 Hour on W202 C180 - Mercedes-Benz Owners' Forums

 

[renault12ts]

You could try oiling the belt...




























































...but don't.

 

[hobnob]

thanks Grober for the advice and Renault for the smile!

 

[hobnob]

I unplugged the MAF sensor today. The result..... nothing discernable really (although I suspect it was slightly worse with it disconnected). This is leading me to think that I may be barking up the wrong tree.

Haynes says:
1. Vacuum leak. But the rubbers all look good to me
2. Spark plugs. Would this not be a more consistent problem?
3. Injector problem/blockage. How would I diagnose that further?

More details on the hesitating. It seems to happen most at lower revs (sub 3k). It happens most when accelerating harder (eg when going through second and third gears joining motorway traffic). The hesitating lasts between half a second and 2 seconds. It feels like I touched the brakes. There is no change in revs.

With clutch slippage there would be an increase in revs wouldn't there?

I'm sold on changing my belt for the other problem. I'll take it off tomorrow and check the pulleys for movement just to rule bearing failure out.

 

[NW_Merc]

With regards to your acceleration and hesitation, if you've checked the spark plugs, have you checked the ignition coils and packs?

You really need to get the car to someone who has Star or other diagnostic equipment rather than buying and changing things ad hoc.

 

[grober]

Is it misfiring? These cars have a reputation for problems with their high tension systems. Hidden under that nice plate on top of the cam cover are a set of plug leads/extenders , 2 ignition coils and some low tension wiring from the ECU. This tends to "cook" nicely being close the engine and leads to misfiring problems.

 

[NW_Merc]

grober is it possible to replace the standard plug leads with aftermarket ones from say Magnecor? Would this give less misfiring and a better spark?

 

[hobnob]

Ok, looks like I'm going into the spark plugs tomorrow then. I don't know if it's misfiring because I don't know what that sounds like (other symptoms?). The engine sounds smooth at idle and at idle the revs are reasonably steady and about 800rpm (or is it 8,000), anyway it sounds ok to my untrained ear.

Diagnostic equipment sounds like a good idea!

 

[grober]

grober is it possible to replace the standard plug leads with aftermarket ones from say Magnecor? Would this give less misfiring and a better spark?

They don't really have conventional plug leads as such. Each coil sits on top of a spark plug which its connected to via a solid extender. The coil also has an "extension" plug lead which goes to a long plug connector. Each coil fires 2 plugs simultaneously altho only one is on its power stroke. there may be aftermarket parts but probably best sticking to MB

IGNITION SYSTEM ELECTRICAL EQUIPMENT

 

[hobnob]

I think I may have found an alternate cause for the hesitation. I have a bought in a service station type fuel cap on the car. Since it just sits in place It certainly doesn't have any vacuum properties. Could this be the problem. Have also been told that it could be a clutch problem because of the lack of power uphill.

It does feel like not enough fuel is reaching the engine, but I'm not sure if a dodgy fuel cap is enough to make it sooooo bad.

 

[NW_Merc]

Throttle body could need cleaning

 

[hobnob]

Probably.