Would this cause running problems?

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Aquiesce

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Manchester
On my V8 the previous owner who did a bit of off roading put a ziplock freezer bag over the MAF and one over the coil, and cable tied the top and bottom. Presumably for a bit of waterproofing, I have had them off but put them back on as I thought they must be OK. However im now having a problem where it will stall when hot coming up to the lights or anytime that I take my foot off the accelerator and coast really. I have a brand new plenum chamber on, new plugs leads,dizzy/cap timing done correctly have cleaned stepper til its gleaming and have substituted it. There are no air leaks or blockages whatsoever and i have just done all diff oils and today the T-Box oil as I thought clutch might be dragging. It will tick over fine in Neutral and park and also when gear engaged it drops a bit too low but will still just tick over its just when moving at speed and coasting in D.
BTW its on LPG too. Im beggining to wonder wether these bags could be causing any sort of condensation as it gets awfully hot under there.
 
However im now having a problem where it will stall when hot coming up to the lights or anytime that I take my foot off the accelerator and coast really.

Although you have changed plugs, cap and leads you don't say anything about the rotor arm nor if the ignition parts were genuine Lucas. Ignition problems with a hot engine can be down to the ignition amplifier (on the side of the dizzy), so might be worth checking that out.

I would also say it might be worth checking that the vac advance on the dizzy is working. Have you set your base idle? Where is your ignition timing set to (for LPG?) Is your idle speed steady or does it fluctuate?
 
Have you got a snorkel fitted?

Yes have a snorkel fitted, have spun it the other way facing backwards as I think i was getting a RAM air effect!

Although you have changed plugs, cap and leads you don't say anything about the rotor arm nor if the ignition parts were genuine Lucas. Ignition problems with a hot engine can be down to the ignition amplifier (on the side of the dizzy), so might be worth checking that out.

I would also say it might be worth checking that the vac advance on the dizzy is working. Have you set your base idle? Where is your ignition timing set to (for LPG?) Is your idle speed steady or does it fluctuate?

Yes rotor arm too all lucas parts, I have a complete car is spares too that was a great runner and have substituted all parts, I did have a dodgy vac advance unit but replaced that last week and the timing definately advances on my timing light now when running. Base idle is fluctuating a bit now. Timing is at around 16 BTDC which seems to be around the going rate listening to most people on here with gassers. As for the ignition amp is that not next to the coil at the front of the engine bay? I thought the only thing bolted to mine was the Vac Advance unit with the diapraghm in? I do have a substitute coil and everything that goes with it so will try swap that out today. As for the bags you think they are fine then?
 
O.K. my bad, forgot later engines had remote ignition amp to avoid the temperature related failures of the earlier ones.

If your timing is wandering I would suspect you may have a stretched timing chain and this could account for the stalling problem you describe. I had a similar problem once and I just couldn't get the engine to run properly, I replaced the timing chain and all was well so it might be worth a look.

On the ignition timing I'll take your word for it but standard timing is about 4 or 5 degrees before top dead centre so there is a lot of advance to run gas.
 
If it's a singlepoint LPG system with an evaporator, then the snorkel is the problem. What is happening is as follows.
The LPG is delivered on a demand basis, ie a pressure difference between the LPG feed point by the throttle and atmospheric pressure causes a diaphragm in the evaporator to move and deliver gas. Works in the same way as a scuba diver's DV. With a snorkel you are creating a separate localised atmospheric base pressure in the inlet tract which is different from the atmospheric pressure at the DV, so you are correct in that you were getting a ram air effect. this will have been causing positive pressure in the inlet tract and shutting off the LPG supply and stalling the engine on coastdown. Same thing happens at a different pressure if you rotate the snorkel head. The way to sort it is to attach a hose to the Evaporator atmospheric port ( on the back in the centre usually a plastic 10mm 90* plastic fitting) and run the hose round to the airbox and plumb it in there. No pressure difference equals no stalling.
Unfortunately you will get a slight pulsing of the gas delivery and therefore engine power. I haven't figured out how to sort that yet.
 
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