W201 running rough at idle

[d_taddei2]

Hello looking for some help. The car seems run rough when at idle and wants to cut out and sometimes does, and gets worse when pressing accelerator, but once up at speed it's fine, could this be the OVP relay? (I have ordered one) however I was told it could be the idle control valve. However when I Google this I get two different images. Which one is it? And is it likely to be the control valve? Mechanic said he doesn't believe it's vacuum leak as it not always happening just sporadically Or is it something else?

 

[Uncle Benz]

The most common thing with these old girls is air being drawn in through the O rings that seal the injectors. They become as hard as rock and because air is getting in bypassing the injection flap the fuelling goes to cock. Spraying some brake cleaner over the injectors with the engine running will highlight it. If the revs pick up they are leaking. As you bring the revs higher it becomes less obvious because the amount of leaked air is much smaller compared to the incoming air.

 

[d_taddei2]

Update. Bought a new OVP relay from Germany. I have it to the mechanic who removed the fuel pump relay so he could get to the OVP relay. Fitted new OVP relay and now the car won't start it's worse then before it went in. Sometimes the fuel pump works sometimes it doesn't. Tried the old OVP relay and fuel pump relay still sane issue. So what can it be?

 

[rayhennig]

So what can it be?

There are some cheapo OVPs on the market that get a bas press.

FPRs are known to suffer too so maybe worth trying a replacement of dismantling and resoldering.

Resoldering old, MB quality OVPs has also been known to work.

RayH

 

[d_taddei2]

As mentioned the OVP relay was from a German manufacturer I avoided the cheap ones. And the fuel pump relay was replaced just over a year ago also from Germany and was original part. I would imagine that after the first fuel pump relay lasting 31yra that this original part would last more that 18 months. I don't do soldering and mechanics no longer do such and auto electricians are no longer