Hi All

My 2010 TDV8 4.4 is now suffering from a bad misfire/stumble...

At idle approximately every second it 'stumbles'/drops revs a little. This pattern is the same when driving - every second it drops power.

History: Battery was flat - recharged overnight - drove it a few hundred yards and the misfire started. It may have run fuel tank empty (the gauge when faulty last week). As soon as it misfired I immediately returned home and put some diesel in. The misfire was still there ... I tried removing battery for 30 mins to 'reset' and a cheap amazon OBB shows no codes

Any ideas?

Thanks, All

Use a diagnostic tool to monitor engine revs. If the revs momentarily drop to zero then most likely the crankshaft position sensor is failing and if so then it will eventually fail totally. Early engine's sensors are known to fail.

GraemeS

Thanks - for the tip - I'll try - can I do this with a cheap OBD monitorr? Mine has a graphing function I think....

It only has to graph engine speed at idle to do the job. Others with the same issue have immediately spotted the short-term zero rpm bursts.

Nice - I see my device has a RPM graphing option - I'll try that next!

Would it also be worth fuelling with a good diesel like V power and trying something like Dipetane?

I use this every few fills to keep injectors clean as its not a corrosive or harsh like an additive. its a hydrocarbon liquid fuel treatment.

https://dipetane.com/how-dipetane-works/

Hope you get to the bottom of it, best of luck Current yokes
2012 4.4 TDV8 Westminster
2006 Disco 3
Scoobie GT wagon
Mx5 G Ltd
TT S Line
Pajero JDM Exceed

Interesting point about using good diesel and an additive.

At the moment I'm wary of driving the car to fill up in case there's something bad happening - my googling quickly found stories of stuck valves, bent con-rods etc when I googled 'mis-fire'

Any got thoughts about how wise driving as she is?

Ya Im paranoid about bad fuel, Ive said this in a previous post but I've never filled up from a small mom and pop type no name garage or the supermarkets. I have always used Maxol, Texaco and Circle K here. If there was a post fuel up incident you at least know they have insurance to cover it.

Years ago a shell garage here got water in their main diesel tank. It took out 11 cars if my memory serves me. They closed not long after.

Now someone may pop in and say they only use Tesco fuel and never have an issue and that's great, its just a person choice for me to limit the risk as I aint rich and cant afford a major engine issue in any car.

Oh and you are dead right not to drive the car at the moment. I really hope someone with more experience with the issue can help you out here. Current yokes
2012 4.4 TDV8 Westminster
2006 Disco 3
Scoobie GT wagon
Mx5 G Ltd
TT S Line
Pajero JDM Exceed

I took a trace using the OBD tool and I never see the rpm going to 0.

So I guess it’s not the CPS failed.

Maybe a blocked injector due to running the tank empty?

Click image to enlarge

The graph doesn't have enough scale to know if rpm does or doesn't drop to zero. The dots along the bottom indicate that revs are sometimes less but you can't tell if it is zero. Can you adjust the display so that idle revs are at least 1/3rd of the way up the screen? It's also possible that your tool isn't capable of showing values for the necessary very short time intervals. If it's showing 1 spot per second that that is inadequate.
IIRC idle revs are 650, so 639 could be the average, reduced by moments of zero.

You probably need a graph from a better tool.

Thanks, GraemeS..

Good points. Sampling seems to be around 10Hz and you're right the device isn't giving me enough x or y resolution.

Is there a well known failure mode here ? ie 900, 900, 0, 900, at some higher sampling rate (900 is just an example of course)?

Cheers
Andy

I don't know the sampling rate but the IIDtool does a good job of showing the dropping to zero.
Mine hasn't had the problem which seems to be more of an issue with earlier engines prior to the sensor part number change.

Is it this?
IIDTool BT G3 for 514 euro ?

That's the latest version of that tool. They're rather expensive if bought for just one use but I find my earlier BT version invaluable for all that it can do.