Im Back! w202 hesitating sometimes

[JimC200]

ok I've posted here before about my w202 c200 hesitating when accelerating not all time but sometimes, its worse when cold, this morning i was in second going along and it felt like it was stalling but then a massive surge of power to bring it back to normal happened after a second or two, I've ruled out MAF and coils and fuel filter they've all been replaced and no joy, I'm wondering now if its fuel pump or injectors? the fuel filter was not changed previously for years and was very choked up changing this made a huge difference but problem remains any ideas welcome, If all else fails I'm ready to bite the bullet and send it into my local mechanic to get sorted, that and the bizarre intermittent extremely high pitched whine/squeal from front at 30-40kmh then disappears completely above this speed is also doing my nut in!!

 

[martyz]

Bosch Maf ?

 

[JimC200]

bosch maf from a working w202 donor car which has no issues so it definitely isn't that

 

[martyz]

Have you checked fuel rail pressure?

 

[JimC200]

Have you checked fuel rail pressure?

nope how would one do such a thing?

 

[martyz]

on the fuel rail pointing towards the block is a long brass nut, this is the cap for the valve,screw a fuel pressure gauge on to this and read off pressures.

 

[JimC200]

ill leave that to a mechanic i don't have a gauge

 

[NW_Merc]

Has the timing chain been replaced?

 

[grober]

If your engine has the adjustable inlet camshaft unit it might be that? There's a small spring in there that can break--- or it could just need cleaning up.[history of missed oil changes perhaps?] PS that's another mechanic job if its that.

 

[JimC200]

Has the timing chain been replaced?

Not to my knowledge there's only 110k on it so I'd have thought it be ok for a while yet, it's odd because it's only sometimes it happens and is worse when cold