valve clearances?? LPG??

[k9]

Okay, I can change a few bit's like air flow meteres and pads, shocks etc.. and service a car but thats about it. My 325i tourer runs on LPG, it runs rough at idle, 400rpm, and uses twice as much fuel as it should, running really rich (had 2 E30 325i b4). Also down on power by 30%, seems to be holding back.

I have changed the air flow meter twice (no difference), cleared out the idel control valve, no difference, changed thermostat, no diffence?

Had a diagnostics test, no fault codes up on it.

Now here is the question, a mechanic I took it too said that running a car on LPG tightens up the 'valve clearances', due to gas not having the lubrication qualities of petrol.

I have booked the car in for this to be done, does this sound right?

Apparently the valves on M20's can be adjusted to give more movement. Is this the same thing as a tappet adjustment?

Would the valves not moving as much as they should cause fuel overload, and 30% engine restricition?

Would be happy to hear anyones opinions.

K

[gcorky]

valve clearances are adjustable but doesnt seem right what youve been told .lpg will make run hotter than petrol aswell.different type of spark plug required aswell.i.e heat range your local parts shop will advise.also sounds like an lpg limitation/setup problem.

[TOURINGDADDY]

that is cod shiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiite mate valve clearences should b .25 no matter wot

[TOURINGDADDY]

has the sys been set up on a gas annlyser or not

[Brianmoooore]

LPG can cause valve recession on cars with soft valve seats or valves made out of something slightly harder than plastercine (like Zetecs), but the problem wont happen on cars suitable for unleaded petrol, except in the case of a few Jap engines where petrol sprays directly on to the inlet valves to cool them.
I've done about 40,000 -50,000 LPG miles on my touring and haven't found them closing up yet.
We need a few more details on the LPG set up. Things like type of reducer (big round thing with water pipes attached to it amongst others), and whether it is open loop or closed loop.

[k9]

Just had my valves adjusted and it is a big imporvment, so a happy chappy at the mo, just need to sort out the noisey diff now

K

[Brianmoooore]

Whatever is (was?) causing your excessive gas consumption is nothing to do with your valve clearances. If they were far enough out to cause problems on gas, they would cause problems on petrol as well.
assuming your LPG set up is first or second generation, it probably just needs a tune up.
The air flow meter plays no part in the operation of the car on gas (1st or 2nd generation). The car would run better (on petrol) without it.