hi all - i know this is a 'how longs a piece of string' question but what are common causes of a rough idle in these... its used to purr like a cheshire cat on startup but now its a little rough - fine when driving. any ideas?

I've dealt with it 3 times since January.. 1st was the rubber seal from the air inlet to the throttle body.. heat had shrivelled it letting in unmonitored air. 2nd was a bad coil pack. Lastly was an injector playing up . Hit that one with some bg44k and it shifted luckily for me..

Meant to say two things - i run a cone filter and have done for a year and hasn't caused me issues. Also it is mildly better on lpg.

How did you identify your issues with diagnostics or just looking around?

if it's dual fuel does it happen on both ?

start the car from cold listen to engine see if you can hear sucking

throw it on a diagnostic machine see if live data helps to show missfire ect

failing all that, may be a good service, and change plugs, if you are LPG what plugs are you running?

how often do you do plugs on these they've bene in about 20k tbh use either NGK-R or Bosch normally can't remember what i went with last time... Oil service was only at xmas but didn't check plugs. it happens less on lpg but it takes a while to warm up to switch over so it may just be because its warmer. also i am convinced sometimes on startup theres a feint smell of petrol under the bonnet...

Dan.. nothing showed on the iid tool.. all I did with the coils was pull them one at a time with the engine running and when I got to the bad pack the engine rpm never changed when i unplugged it..the other issues where trial and error

I'm guessing the dead cool made it run rough on driving too which mine doesn't?

Danwilderspin wrote:

how often do you do plugs on these they've bene in about 20k tbh use either NGK-R or Bosch normally can't remember what i went with last time... Oil service was only at xmas but didn't check plugs. it happens less on lpg but it takes a while to warm up to switch over so it may just be because its warmer. also i am convinced sometimes on startup theres a feint smell of petrol under the bonnet...

Just ran for 100 miles yesterday on petrol still lumpy on petrol idle fine on gas even after that.

Also not sure if it's related but after driving whether on petrol or gas you can smell petrol from the side of the car near the filler. I put a new seal on the cap but not done anything....

so other possibility is a fuel leak somewhere, check all lines from tank upto front of the car, what LPG system do you have installed? some can be forced to start on gas so you could rule out a cold start problem or a petrol start problem

Yea I have a zavoli system so I could try a cold start by holding it on a warmer day - also had the tank covers off no obvious leaks didn't go all the way to the front as ran out of time but there were no stains or anything

you may not get a stain, if the leak is slight dropping the pressure on the rail you pipe would get wet but would soon evaporate leaving no signs, next job check fuel pipe and return pipes tank to fuel rail and back,

could also be an o ring on petrol injector sucking in air instead of leaking fuel

Hi all thought I'd better reply - it ended up being the purge valve. Got a quote from lr £105 plus vat ... then gave my part number to bmw £55 all in! That one hell of a markup lr must make...

Anyway I changed it you don't even need tools the pipes are push fit and now I have a nice idle and no horrible stink