Hi all new to this page, 

i have a issue with my 2001 x5 4.4 v8 on cold starting in a morning it runs rough but still revs fine and once warms up is fine after using the car for a while it develops a misfire like it’s dropped on 1 cylinder but when you turn the engine off then back on is fine for a bit then does it again, I’ve changed the plugs and all where fine with just a slight tan colour on the ends so all firing fine I have a set of coils on order so I will be changing those, it’s worth mentioning the car is also gas converted, when it’s not missing it drive beautiful with bags of power so I know it’s something stupid so any ideas????? 

Thanks in advance 

 

 

Hi Ian...welcome to the Club

It does sound like the LPG system is playing up as once it is past the startup phase then the LPG kicks in I would suggest checking that for a defective injector.

As for running rough on startup....that could be a completely different issue but not related to misfiring....check all vacuum hoses for leaks which may cause those symptoms.

Hi cheers for that it also misses on petrol too so I’m not sure if it would be the lpg system, it’s just the weird thing that when it’s misfiring you switch off the ignition and back on and it’s fine I’m going to be removing and cleaning the throttle body too

was thinking that when it starts up it would be on petrol and not LPG so there may be underlying issues on both systems....definitely worth checking codes and data from the ECU to determine what is causing it

So I got home and it started to develop a slight misfire so I disconnected the maf and the engine started to run smoother, would this point to a bad maf?

Usually when you disconnect the MAF the system goes into a default running mode and substitutes the sensor reading with a static value which in fact most of the time allows the car to run smoother than if connected...which is also a good diagnosis to prove that the sensor is defective.

You could try cleaning it and see how that works (carb cleaner and Q-Tips tends to work)

Thanks all for the replies the problem is fixed fingers crossed it stays that way the problem was one of the lpg injectors has failed which was causing the engine management system to cut out that coil on that cylinder which meant when I was running on petrol it was the same 

 

thanks again 

Glad you're getting to the bottom of the problem and sorting the issues

Glad you found the issue.

When was the LPG system last serviced do you know? There are a couple of filters in there that need checking/changing as well (well mine did) I used to have it serviced once a year cost about £90

When I brought the 4.4 it had LPG installed great but when I gave it the beans it would misfire then go back to petrol, I found a local LPG specialist who turned out to be the original installer (how lucky was that) he serviced it and upgraded the software then it ran like a dream.