Slugish and cutting out.

[Chris m]

2010 ST, 237,000km, auto. Cuts out sometimes if revs get below 2k, no power sometimes from standing start for about ten seconds then jumps into gear. Idle good some days terrible others. Thoughts? Just did timing chain, dpf, ecg pipe. Been on and off for over two years.

 

[kernels]

Suction control valve ? Probably the single most common problem on yd25s

 

[Chris m]

Cheers. Its been the most frustrating period of my life, yet rather rewarding for my mechanic.

 

[kernels]

lol, no worries, have a browse and search for SCV (suction control valve), it's the part the engine uses to control the pressure of the common rail. Not too expensive to replace and can often be cleaned instead of replacing. About half the threads in this section describe various symptoms of a dodgy SCV

 

[Chris m]

Fingers crossed its that simple. Thanks again

 

[Old.Tony]

Yeah I'd wonder about the SCV as well, especially with the rough idle.

If it were just down on power you'd probably look more towards turbo/actuator/vac hose/solenoid/brake booster but the poor idle aims this one squarely at fuel/timing.

There's a small chance that it could be a stalled turbo impeller which will block the air intake rather thoroughly, but that's easy to check. First, with clean hands, remove the hose from the front of the turbo and spin the impeller (cold engine). It should be a little resistive but not rough to turn over. All good? Reconnect the hose, do up the clamp, start the engine and take a look at the little gold arm that's underneath the actuator. It should be moving in and out about 3-5mm in total. If these are ok, your turbo (and hoses, solenoid etc) are likely to be in good order so you're looking back at the SCV.

Clean the SCV first just in case you can save some $ there. Rinse it well in fresh diesel before reinstallation.