98 clk230 komp down on power.knocking in engine

[brickie]

hi lads, my merc is down in power, when you rev her out she only goes to 4000rpm, the wife was driving it today and she said the car was down on power and heard a knocking sound from the engine, i asked a mate to take a look he reckons the exhaust could be stuffed, when you rev her out the exhaust is red hot at the back,i drove the car there half hour ago and she was driving fine then, no knocks r bangs, anyone any ideas of what it could be,the car has 150k miles on her and drives great until this. thanks lads

 

[Uncle Benz]

Sounds like blocked cat or blockage in the exhaust to me.

 

[brickie]

would that cause the knocking in the engine?

 

[Uncle Benz]

In my experience, yes. As back pressure builds up it will become more difficult to expel all the hot exhaust gas from the cylinder on the exhaust stroke. Some hot gas will remain, and it lights the fresh charge too early. That is exactly what pinking is - pre ignition.

 

[brickie]

cheers uncle benz, is this an easy fix do you know? would it do the car any harm if i drive it, ive to take it to my mechanic in the morning which is 10 mile away, he,s going to put it on the computer, i have no warning lights on with this problem, cheers

 

[brickie]

drove my clk yesterday before bringing it to the mechanic, the car was driving fine again,i drove about 40 mile without any problems weird, it has to get sorted anyway