OM642 High Tickover

[PaulMason]

Evening all, my 2008 ML320 CDi (coming up to 126k) has a bit of an oddity. It seems to have a bit of a variable tickover. Sometimes it's 1,100, sometimes 1,000, sometimes it settles at about 750rpm. I initially thought it was the Pro Diesel Chip that it came with (which I removed and surprisingly lost about 2mpg having thought there was no chance it actually did anything) but that didn't change the tickover variability. I am wondering whether the battery is beefy enough/unhealthy (is the ECU making the car tickover a little higher to get some more current into it?) Anyone got any ideas/guidance at what to look at first. It's no real biggie, just a slight annoyance and bugs me and makes it creep a bit harder than it should when queuing. Thanks in advance as always!

 

[TeddyRuxpin]

When the car is cold (under 12 degs outside) or doing a DPF regen, the car will idle higher

However 1100 is very high.

On an OM642 the idle is usually 750-800 when cold/regen, and 550rpm when warm

 

[Jobsworth]

Try lifting the throttle pedal. They can stick a bit when they age.

 

[TeddyRuxpin]

Good point @Jobsworth, the creeping thing seems to suggest that throttle is actually being applied vs it actually being at idle

 

[PaulMason]

Thanks both, looking at some Google results there is some comment about a throttle pedal issue causing similar symptoms so I'll lift the pedal to see if that solves anything and also do a TPS reset (which I assume is the same one a ML as my S)

 

[Smart320]

My first ML had a similar problem, eventually needed a new accelerator pedal , just changed the complete unit, disconnected the old and plugged in the new one , everything was immediately back to normal.

 

[PaulMason]

So, lifting the throttle pedal does definitely drop the RPM at tickover, last night from 1,000 to about 820 so still a little high. I suspect it's both a little sticky and also the potentiometer is a bit duff. Next step is to buy a replacement from eBay and see how that goes.