Diseasel question

[wuvvum]

The Rover of Doom has started misbehaving over the last couple of weeks, and I know naff all about diesels so not sure what is likely to be causing it.

 

Basically, when rolling along on a light throttle (at a steady 30 or 40 mph) the car will sometimes stutter and judder a bit, almost like a petrol engine feels when it has a bit of dirt in the carb or whatever. It's not enough to stop the car being useable but it's enough to be irritating in town, especially at the moment as the traffic is lighter due to the gobshites being off school so I spend more time sitting at a steady speed. It's getting gradually worse too. It still idles fine, and it runs perfectly well under acceleration and is just as quick as it always was. It gets better as speed rises and runs fine at anything above about 50. Fuel consumption doesn't seem to have changed and it isn't smoking any more than normal either.

 

I tried giving it an (extensive) Italian tune-up yesterday in case it was just getting coked up with all the pottering along in commuter traffic, but that hasn't done any good. Is there anything blindingly obvious that could be causing it? I don't want to take it to a garage if it's something that I could fix myself using a hammer.

[Rocket88]

Change the fuel filter?

[dollywobbler]

Fuel and air filters would be my first thought, but these are known for having MAF issues. If it can't accurately measure the air flow, it will not be able to supply the correct amount of fuel (if I understand these things correctly). Hasn't yours got one of those tune-up gubbins on it? As well as the performance hike, it's also meant to help get on top of this sort of issue.

 

This is a crap-looking website run by someone who understands these engines, so it contains good informations. http://tuning-diesels.com/

[wuvvum]

I did wonder about the filters, but if the fuel filter were getting clogged up then surely that would affect the performance (or at least make the engine splutter) under full throttle? How often does the filter need to be changed? It had just been done when I bought the car so has only done about 10,000 miles. Air filter is an aftermarket K&N which hasn't been on there that long, but I might take it off and clean it anyway just to be on the safe side.

 

That website looks like it could be useful, cheers for that - might be worth taking the MAF out and cleaning it to see if that makes a difference. Will try it at the weekend if it isn't pissing down.

[Albert Ross]

Fuel filters are susceptible to clogging if poor fuel has been run through them. All it takes is a tiny bit of water to expand the paper element to such a degree that diesel fuel won't flow through it. Replace it first, then report back.

[Cavcraft]

Another vote for the fuel filter. Had a couple of problems like this with diesels in the past and new filter sorted them. Worse one was a Transit with what looked like a near new filter on it, local garage told me to lob a genuine new one on and it cured it instantly.

[scooters]

The Mondeo that I've just fixed at Diamond Dikkies Diesel Diagnosis had a fuel filter full of slimy bacteria..it grows in diesel and shuts out hydrogen dioxide which causes all sorts of issues as above. Change the fuel filter and look at the crud in it. If it has gunk, either hard small spotty yellow lumps...not very many, doesn't take many or thin snit invite filter then bacteria. If it has steel filings then replace the fuel pump...it's borked.

[Danblez]

My focus had similar issues with the egr valve. Does the rover of doom have one?

[scooters]

Diesel specialist I spoke to recently suggested that after a tdci hits about 100k just to blank off the egr valve ...more hassle than its worth really.

[dieselnutjob]

I was thinking EGR as well. Part/light throttle is when the ECU will dial in the most EGR.

[Morgan84]

What model of Rover is it ? Yes,a fuel filter will be the first port of call,as may a fuel system conditioner

[wuvvum]

I bought a bottle of fuel system cleaner last night - I'll tip it in tonight when I top the tank up. I'll also nip into Halfords on the way home and see if they have a diesel filter in stock - hopefully that will cure it. The car was noticeably worse this morning - it was chugging quite badly at 50 in 5th - so I need to do something about it sooner rather than later. I'm just hoping it's not the tuning box starting to play up - although I think that's unlikely as when these things go they usually go completely. I think the SDi does have an EGR valve - I'll look into that further if the filter doesn't sort it.

[scooters]

,

Diesel, as I am sure you know is horrible, nasty, smelly disgusting stuff...trust a Frenchman to come up with the idea of using it to power motors!

 

When it combusts it gives off thick nasty horrible oily smoke, now the big problem with older 'modern' diesels is they have to be clean to work, these can get covered in horrible carbon crap...think mixing syrup with tar, oil diesel and ash and the consistency of this gunk. Waving some Miller's at this is a bit like trying to wash a pikeys transit with some head and shoulders It's even worse with a turbo because you always get a bit of oil entering the intake system, engine breather doesn't help and the egr taps it all off by dumping sooty smoke into the combustion...this creates a vicious circle as the shit going in makes more shit going out and that goes back into the engine again.

 

Before you spend any money on bits you should clean the whole inlet system.

 

So, get an old washing up bowl that you don't want to use again, a selection of scrapers , ideally plastic an wire brushes, kitchen towels old newspaper and about 6 cans of carb cleaner.

 

Order a new inlet manifold gasket and get on eBay and order a blanking plate for a fiver egr valve, cost you sa couple of quid and list of folk make them or you could make one yourself. Get a tube of blue gaseal.

 

Take the egr valve assembly and the inlet manifold off the car, they will be caked with the disgusting sooty mixture I have described, clean the whole lit out best you can, dry it off and put it back together using gaskets, blanking plate and gaseal

 

Then take the car for a 100 mile Italian tune up do the efi learns the new air flow .

 

Only after this do you need to start looking at other areas.

 

But change that fuel filter as well..

 

You see, we spend money on air filters but older diesel engines caked with exhaust soot deposits, and you will he horrified at the amount of soot...the Mondeo I just fixed had a centimeter of the stuff, make the inlet air filthy..

 

If you get stuck or need more advice call me on 07950399564

 

Rich

[The Moog]

If it is gunked would something like seafoam help?

[wuvvum]

Right, I changed the diesel filter this morning. Nice easy job, took about 5 minutes, but it's made feck all difference. So that wasn't the problem. I tried running it with the air filter off and that didn't help either.

 

So it looks like I might have to embark on open heart surgery as Scoots has described. There's a couple of other things that might be worth checking before I do - the MAF sensor has already been mentioned, and I don't know if muck in the throttle potentiometer might cause the same symptoms? I have no idea how potentiometers work.

 

The thing that puzzles me is that it only has a problem on light throttle settings. It's fine with the throttle at idle, and it's fine from about 1/3 to full throttle, it's just the bit in between. If something were badly clogged up I'd expect it to affect the engine all the time - and possibly even getting worse under full throttle. Like I say though, I don't know a great deal about these things...

[scooters]

It can take a while for the fuel filter change to make a difference - because the arteries will still be a bit clogged especially if bacteria bloom was evident. Also with some cars the ECU needs to 'learn' the new conditions so you can't really make the call for 100 miles or so.

 

Before addressing any of the sensors etc I do recommend the procedure above - unless the system is in good cleanish condition especially air and fuel flow then these diesels can behave in very weird ways. If you start addressing it in an un-methodical way, you can get lucky but more often than not it costs time and money.

 

If after following the procedure you still have the issues - again you won't know for a bit, then you will need to read the error codes from the engine to help narrow down the fault. Replacing the cheap sensors is a good idea - and cleaning the expensive ones.

[4x4xfaz]

MY 2 CENTS WORTH....

 

It is quite likely to be fuel related.

Dirty diesel filter - dirty fuel lines.

Split or cracked fuel lines - air leak (or suction)

Bad fuel pump seals - can result in erratic behavior at certain revs.

 

Might be .... Vaccuum pipe ... pcv valve ... egr valve ....

 

And surely it could be NONE OF THE ABOVE!

[myglaren]

The thing that puzzles me is that it only has a problem on light throttle settings. It's fine with the throttle at idle, and it's fine from about 1/3 to full throttle, it's just the bit in between. If something were badly clogged up I'd expect it to affect the engine all the time - and possibly even getting worse under full throttle. Like I say though, I don't know a great deal about these things...

 

Not to discount any of the other advice offered but you may have hit it right there - dirty or worn throttle pot tracks at the point the throttle most often sits at.

[wuvvum]

On closer inspection, the EGR valve has already been bypassed.

 

Time to start taking things apart then...

[wuvvum]

Typing this with one hand as the other is firmly touching wood, but it appears the Rover is sorted - it seems the problem was a broken wire from the throttle potentiometer. Was a bit dubious at first as it looked like it had been cut rather than snapping of its own accord (although it's hard to tell for sure with a wire that thin), but joined it back together anyway and so far the car's been behaving a lot better. Which is good.