TD4 lumpy misfire

My 2004 td4 HSE auto 88k has developed a reet annoying misfire or summat and its doin mi head in.
After a 90mile motorway run during which it ran fine engine began to 'hunt' on tickover and had a misfire upto about 2500rpm. Changed all vacuum pipes to turbo etc as soon had chaffed through. Cleaned out inlet manifold and blanked off egr. However when I'd done had a blonde moment and put 30lts unleaded in(1st time in 33yrs) anyway drained all the lot out after driving the 2 miles home and refilled with diesel. Misfire, hunting and lumpiness gone, hardly any black smoke and better performance Result ? Well at first yeah but symptoms are creeping back.
Misfire I would describe as similar to a petrol with a weak spark on one of the plugs. Try and maintain 1200 - 1500 rpm rev counter falls away to less than 1000 and then returns . Idle seems steady. Any ideas without off to stealers to get fleeced ? Could fuel rail sensor cause this. No loss of power and runs sweet at motorway speeds. This is my second freelander and its doin mi ed in beginning to think should have stayed with mi v8 disco but 12 mpg wasn't good
Thanks

Had the same thing, the garage (DCV) said that they changed the crack position sensor that made no difference, but cleaning the crap out of the EGR cured it. Could have been a combination of the two I guess.

Hi
I had a similar problem on my 3.0d X5, turned out to be as simple as a dirty injector, problem solved by dumping a bottle of diesel injector cleaner into a quarter full tank of diesel and then ragged it for half an hour. Filled up the tank after and was like a new engine!
Hth
Gareth

Forgot to say doesn't do it when cold just when engine warms up and no warning lights on !
Tried the millers after the fuelling mishap.
Grrrrrrrrr
Sheriff

I've recently had similar problem, see thread 05 td4 irregular throttle response, idle lumpy and couldn't hold revs steady below 1800rpm but mine was worse when engine cold (very under powered)
was a faulty injector.

Cheers guys, ready for taking 14lb striking hammer to the flipping thing. Off to local independent this week for a twirl on test book. Other than this flipping low rpm misfire and chronic diesel knock at low revs she's flyin and no smoke too ! am betting defunct injector. German engineering ha sh*te. Don't know about FREElander more like skintsyalander !

Off to garage tomorrow, misfire gettin worse and now surging around 1500rpm. Grrrrrrrrrr

Back from garage weekend all sorted will be fitting a new No1 injector. It gave a reading of 4.98 which apparently is way off the mark and means it's all abouts fooked. Replacement injector on order will be avail tomorrow, so will let you know how the installation goes.
Fingers crossed. Sheriff