Engine surging

[Kameron1]

hi i have a problem with my ml270 w163 when I'm on the motorway at around 70ish the engine starts to surge and the revs are up and down it only does it on the motorway town driving is fine the gear box all works fine i have no smoke out of it at all the problem is driving me nutts please help

 

[alecmascot]

Sounds like fuel flow.
Fuel filter. fuel pump, injectors pressure sensor.
Get it on a scanner and see if there is anything logged, and read the fuel pressure when the fault occurs.

 

[Martyn_n]

Does it do it when it's on cruise control? If not it may be a faulty throttle position sensor. I would expect issues with fuel pressure to send it into limp mode.

 

[Kameron1]

Sounds like fuel flow.
Fuel filter. fuel pump, injectors pressure sensor.
Get it on a scanner and see if there is anything logged, and read the fuel pressure when the fault occurs.

Right ok thankbyou for your reply I can smell diesel when I've been on a run the car has recently had a fuel oil and air filters done but I could smell fuel before these were changed

 

[Kameron1]

Does it do it when it's on cruise control? If not it may be a faulty throttle position sensor. I would expect issues with fuel pressure to send it into limp mode.

Hi thank you for your reply yes the car does still do it when cruise control is on if i put my foot down it drives fine until its under load again

 

[horatio]

I would expect issues with fuel pressure to send it into limp mode.

Not necessarily. My CLK 270 had terrible surging at idle which was caused by the fuel pressure regulator at the end of the rail. No dash light or codes. £50 part, 5 mins to replace - annoying I only figured the cause after a garage needlessly replaced 2 injectors

This could be so many things, get the codes read no.1.