Sudden idling issues and then stall :(

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TCubed

Active Member
Posts
991
Location
Surrey
Hi chaps,

DHSE: Driving home tonight, stopped at a light, and the engine wibbled around 800-1200rpm (normally absolutely steady on ~900). Started moving again as soon as it started and was fine for a few miles, then did it again (again at lights).
Fine fine fine fine, got to stopped to engage reverse to enter my driveway.. and it stalled! Moment of terror when it wouldn't crank... changed from D to N :p she started up, gave her a quick rev and rushed onto driveway.

Sooooo.... Thoughts? I've seen about MAF (forgive my ignorance but what is this?), air filter and fuel filter. Both filters have just been changed by me. Tank is about 90% full of diesel.

Thanks :)
 
MAF - Mass Air Flow meter, this device measures incoming air density....

There is usually a discussion about the function of the MAF on the diesel by the two diesel gurus on here, Wammers and Datatek, about what it is there to do, but lets try and not stir that up again as it can last for a few pages...but it. Was introduced along with the EGR (Exhaust Gas Recirculation) valve to help reduce emissions to meet the regulations.

The data from the MAF is used to determine how much recirculated exhaust gas is admitted into the intake to control emission output.

Wether or not the EDC (Electronic Diesel Control) system uses MAF data to adjust fuelling is the big discussion, as RAVE is not 100% clear on this, and the respective arguments from the two big hitters is compiling in both cases. I don't know the diesel system well enough to add further comment on this....

In your case, how are the gear changes? If it was sticky getting into reverse, it might be gearbox fluid related be it old oil or sticky valves...
 
ah ok, air sounds less scary than I thought it could be. Potentially could it be dumping exhaust gases in there then? does this just require cleaning (simple as that would be blessed!) or worse..?
gearbox oil has just been changed fully (2 changes) so it had better not be iffy... I'm not certain if it only did it while in D or in N as well. It engaged R fine. Changing up through gears was same as ever, and ever I think is ok :p
 
Nothing to do with MAF that is for controlling EGR. Engine should be idling at 750 RPM +- 50. Cause of stalling is fuel quantity servo fault or losing signal from CPS. I would suggest your car has been set at 900 RPM for a reason. Quite often fuel quantity servo problems can be masked by increasing the idle speed.
 
wammers said:
Nothing to do with MAF that is for controlling EGR. Engine should be idling at 750 RPM +- 50. Cause of stalling is fuel quantity servo fault or losing signal from CPS. I would suggest your car has been set at 900 RPM for a reason. Quite often fuel quantity servo problems can be masked by increasing the idle speed.
Click to expand...

OK, what could suddenly cause it to go like this? Does it explain the wibbles that occurred above idle rpm? Is there any point in putting some cleaner through the fuel system?
 
wammers said:
It has a pressure chamber, any water laying in that will be injected at some stage it cannot get out any other way.
Click to expand...

When I had my pump rebuilt it was so rusty in there where water had been sitting for long periods either the previous owner was lacking in fuel filter changes or it sat in it for a long time the worst they had seen for a long time so they must hold water :)
The wording was water contamination .
 
TCubed said:
but shouldn't any water be contained in the filter :/
Click to expand...

That depends on how much water has been pumped through. Under normal circumstances yes. If it's flood how much can the filter hold. Any water put in the tank will go to the bottom and be the first thing picked up by the lift pump.
 
Grit Valve said:
When I had my pump rebuilt it was so rusty in there where water had been sitting for long periods either the previous owner was lacking in fuel filter changes or it sat in it for a long time the worst they had seen for a long time so they must hold water :)
The wording was water contamination .
Click to expand...

The only way water can get into the injection pump is if it is pumped into it by the lift pump from the tank. You cannot get condensation unless the fuel contains moisture. Under normal conditions it doesn't.
 
wammers said:
That depends on how much water has been pumped through. Under normal circumstances yes. If it's flood how much can the filter hold. Any water put in the tank will go to the bottom and be the first thing picked up by the lift pump.
Click to expand...
ok, I'll drain the bottom bit and see if there is any water, if there is hopefully that'll sort itself in a few days once more fuel goes through. If there isn't.... What would be the next thing to check?
 
So I drained a little fuel from the filter - pure diesel and a bit of fluff (I think from the Tupperware), but no water. Then I screwed the filter on much tighter (by hand only) as there was a film of diesel around the top.

Started up and in the first couple of minutes there were major seeming misfires, erratic idling and finally stalling when I revved her.
However upon restart she ran smoothly (same as ever at 948rpm Wammers?). Engaged D and R in both high and low range, and the revs dropped a fraction as usual initially but then restored. Braved to drive off the driveway and do a lap of the block (engine warm by this point).. no mishaps :)

So.. do we think I just failed to properly tighten the filter and so air was getting in? Or has the problem just paused until I least expect it :p
It seems like I've driven a long way (~100 miles) with the new filter.. but maybe it was getting shaken looser and finally became loose enough to let air in...

Would be adorable if that was all it was.... :p Thanks for everyone's help if that's all that needs doing :)
 
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