Hi folks, looking for any help or suggestions on what's causing the following issue.
My 4.0 XJ has recently started to run really rough and clunky between about 1400-1800 revs (usually seems to be around 40-50mph), when going up any sort of hill (even a small incline) and especially if I've had to slow down for a junction etc at the bottom. Once it gets past this and up to 2000+ rpm it runs sweetly and will happily cruise along the motorway at 70 without any complaints.
I was also having an occasional little judder when sitting idling, so initially suspected it was just a missfire causing the problems so I've given it a full service, new plugs & leads etc but while the idling judder has cleared, the revs issue is still there. Noticed on some other posts here that the O2 sensor has been a culprit for some similar issues people have had, but they all seem to have been at higher rpm (3500+), whereas I'm having no problem at all at higher revs.
I've had a lesser version of this issue before, where if I'd been driving for a few hours straight, I'd start to get a bit of a juddering feeling (at any speed/revs, not just in the 1400-1800 window I'm experiencing now). It felt like there was maybe an issue with the fuel line somewhere, however I found that a bottle of Redex once a month has kept this issue at bay.
Any ideas?
