stumbling/hunting running when warm.

On petrol arround 30, when warm after a motorway run, it stumbles and hunts when driving, and won't idle on petrol. Can't get it to hold a regular idle speed.

Was idling very rich, but since I sorted the idle mixture to 2.0 CO, it now drives worse than before.

If I can get my hand behind the back of the block, I'm going to change the vac hoses this weekend (and get a vac hose to get a reading). The LPG coolant hoses get in the way of easy access. I have changed the plugs and dizzy cap, was thinking maybe that changing the coil/rotor arm might help, but it drives so smoothly on LPG. When I first got it, I changed the leads, but it wouldn't run at all, so I put the old ones back on and it fired up straight away.

BTW, how do you disconnect the power connector to the idle air bypass. Apart from space being tight, I can't see how to remove the metal spring clip to free the connector.

Is it likley to be fuel pressure (vac hoses to the regulator), or ignition (coil).

I've enjoyed driving it, but I'm beginning to think if I can't it idling cleanly and idling on LPG it is going to have to go.

I'm using about £40 of petrol (stop start driving about 15 miles a day) and £16 of LPG (when on the motorway as long as I don't need to stop or slow to quickly it is fine) a week. Total about 220-250 a week for about £56 of fuel. Auto nice, V8 growl nice, wallowy from lifted from suspension actually not that bad. Fuel bill scary, and constanly shifting idle (I always seem to be turning it up) a real pain in the arse.

Sounds like you ahve a problem or two. This is just an opinion, but I am guessing you have a flapper rather than hot wire system. If so you need a device to hold the flapper open, for a couple of good reasons. The flapper acts as a restriction, not good bearing in mind that the gas mixer venturi further restricts the flow of air. Seconldy if the system runs low of lpg or for any other resaon leans off it is prone to back fire out of the inlet tract, and will destroy the flapper if not lifted out of the way. Now the poor idle on lpg is not maniflod depression dependant, the vapouriser has a minimum flow setting which is adjustable, hence the idle fueling is not dependant and or related to the fueling under load. If you have a reasonable system it will have a filter on the lpg side, this may be clogged. I have worked on systems with various filters some times a seperate filter housing and sometimes inside the vapouriser, and on cheap systems no filter at all. The mixer you have may or may not be up to much. Whilst most 4 pot carbed engines are easy to run and run well on LPG to the point that I used to make my own mixers, the rover V8 can be a pain. This is because they do not create much in the way of manifold depression. The way most companies get round this is to fit a mixer which really restricts the inlet tract and increases depression, thereby making the vapouriser work at the expence of top end engine power.

Wish you luck with it.

Simon

Simon, yes, on flapper. I have a Chris Perfect/Iwema flap opener, the power is ok (run of the vaporiser power leads), but I can't seem to get a strong enough vacuum to open it, hence why I planned to get new vac hoses.

I've tracked down the stumbling BTW. It had a cheap foam/wire air filter cone fitted. The foam was prettty badly broken up. I replaced it with another cone, but this is somewhat bigger with chrome instead of paint on the steel end caps. As the coil has been moved, and lpg gas and coolant hoses all pass through that area, it was pretty tight. I don't know if when the bonnet was closed the it was getting too hot, or was shorting on the bonnet and the coil, but since I put the old barely useable filter back on, it still idles low, but doesn't stumble when hot, or die so easily. And that filter goes nowhere near the coil.

Just need to change those vac leads, get a vac guage to see what reading I'm getting and get that flap opener working. I'm thinking maybe a one way valve in the vac line, so that the vac pressure can suck open the flap opener, but trap the vacuum until the iwema vac switch releases it.

Thanks. That will be my next of call. See my reply to Simon about the electrical stumbling.

You ought to do a leak down test as well, if replacing the vacuum hoses doesnt improve the idle vacuum, you've got to look at poorly sealing inlet valves...

Tim..

I'll be honest. If that turns out to be the problem, it will be going. It was bought as cheap tatty fun, not as a rebuild/resto so I'm not going to be putting large sums of cash into rebuilding the heads.

Or even tappet jack, though i'd think this pretty unlikely on the rover v8 given how little oil pressure they run..

Tim..

I bought it for =A3560 and put a years ticket on it. With the =A3100+ I pai= d=20 for the Iwema flap opener+ a few service bits, I'm not planning on=20 spending much more, otherwise I'll get into the "fixing cost more than=20 it cost me" situation very quickly.

--=20 Carl Robson Audio stream: