disco 1 3.9 running problems

hi guys, first post on here so here it goes!!! right my disco started to lose a bit of power and vibrate when accelerating.the vibration stops when you lift off the throttle. it does it on petrol and lpg. have put on new plugs, rotor arm, dizzy cap, leads,coil and cleaned the air flow meter with some carb cleaner. but none of this seems to make a difference!! help please

anyone have any ideas?

Hi Robbie, Sounds to me like you,v done all the easy, on the engine.
Have you looked at your propshaft joints? they will surely wear with v8 powering through em, i know its a long shot but look anyway.

robbie rotten said:

hi guys, first post on here so here it goes!!! right my disco started to lose a bit of power and vibrate when accelerating.the vibration stops when you lift off the throttle. it does it on petrol and lpg. have put on new plugs, rotor arm, dizzy cap, leads,coil and cleaned the air flow meter with some carb cleaner. but none of this seems to make a difference!! help please

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I know how you feel chap. my 3.9 can also be a bastard to get consistent running and performance.
You've done the right thing in making sure the ignition system is tip top, remember that for LPG you ideally need to have a slightly smaller spark plug gap and advance the timing a smidge.
Are there any noises to accompany the vibration? (steady!!! )
If so, where from?
Are you sure it's running on all 8 cylinders?
Are you getting a misfire when on LPG?
When was the last time the UJs and propshaft joints had any grease?
I recently fitted a new vacuum advance unit to mine and it made a huge difference to the performance, so check the vacuum advance on your distributor is working/no leaks and the small pipe is connected to it from the plenum chamber.

thanks for your replys,will try what you recomend and see how it goes..

thanks tony and boomer turns out the uj's on the front prop were on the way out.all sorted and as smooth as silk, well as smooth as its gonna get anyway..thanks again guys