Low idle

**bee utey** · 24th February 2015, 08:42 AM

If your breather hose from the drivers side rocker cover is connected to the inlet duct, remove it ASAP. It should remain connected to the port on the side of the throttle body at all times. The way the LR breather system works this is the best way. Fitters that hook a breather into the front of the mixer think that the LR breather is the same as Holdens and Fords with a PCV system, which it isn't. As Philip said, you need the tee piece with the small vent to the inlet manifold. The size of that breather sets your base idle speed as much as any other component. Go get a genuine one, they're not that dear (I paid $18 for the last one).

The problem with moving the breather is that the engines dirty fumes are being put into the throttle body in a way that they enter the IAC valve and goop it up. With the stock breather only on full throttle do fumes enter the throttle body and they are drawn through on the front side away from the IAC so don't enter it. At low throttle the fumes are drawn into the engine via the small branch of the tee. It's really quite clever and LPG fitters do love ruining it.

This is a home made brass tee, I had to reduce the small hose outlet with an internal jet of around 3mm to correct it.

Note the mixer, it's one of mine at 46mm ID, see below.

As to the mixer ID, the maximum size that a 3.9 can run successfully is around 46mm. Most of the off-the-shelf mixers are around 42-44mm and will reduce your top end power a bit, you may lose say 500 rpm off your power band. Down low you'll never notice it. I've re-profiled plenty of mixers in the lathe to increase their ID and make sure the gas outlet channel is as clear as possible.

Oh and do get some o-rings for the MAF, they're easily lost so keep a spare handy. I make mine by super gluing cut down larger ones out of a random collection I once got at a garage sale. You can probably buy bulk o-ring rubber at a bearing shop.

**DoubleChevron** · 24th February 2015, 09:04 AM

Thanks for that picture.... A simple picture speaks a thousands words sure is true

I'm pleased we have some gas guru's on here ... 'cos I'm sure my uncle would have said "that's right the way it's done" too as he's not into "rovers" at all. He hates old cars, he'd have told me old Rovers are unreliable heaps of **** and get rid of it ( gotta love grumpy old mechanics, he'd say the same thing about my citroens too

).

OK, I'll chase up one of those brass fittings. I'll have to find a new non-butchered bit of flexible intake hose too.

The gas installer has done such a nice job in some places.... and such a ****house job in others. The gas gauge also doesn't work. I know the float is working as you can hear is squeaking as it moves around under 1/2tank. I imagine it's not wired in.... (or the sender in the tank is cactus). I'll have to try and find the wiring schematics for the gas system to figure it out. I'm not in a hurry to take it back to the guy the installed the gas.

The gas gauge doesn't really worry me ... just keep a quarter of a tank of petrol in there at all times and switch it over if it runs out.

Hey Bee utey, have you tried one of those BLOS gas carbies. I googled it and they seem to have a very positive following

seeya,
Shane L.

**bee utey** · 24th February 2015, 09:25 AM

Originally Posted by DoubleChevron

Hey Bee utey, have you tried one of those BLOS gas carbies. I googled it and they seem to have a very positive following

Never been tempted, they look like a device like the equally well loved hiclone to me. Even the biggest available one seems a load smaller that a plain well profiled 46mm mixer. I think their heyday was in the eastern european dark ages before sequential vapour injection transformed small engine performance on lpg. IMHO don't mess with a simple easy to sort system unless you have a passion for complexity. Then go for SVI and electronic tuning instead.

Oh and I just checked my spare breather tee, the jet size is 1/8" or just over 3mm, not 1mm as first mentioned.

**PhilipA** · 24th February 2015, 10:54 AM

Specialists like Graeme Cooper used to sell a ready made brass "T' with the correct holes as the OEM ones are plastic and die over time or if disconnected too many times.
they probably still have them as there are a lot of D1V8s around
Regards Philip A

**DoubleChevron** · 24th February 2015, 12:08 PM

Originally Posted by PhilipA

Specialists like Graeme Cooper used to sell a ready made brass "T' with the correct holes as the OEM ones are plastic and die over time or if disconnected too many times.
they probably still have them as there are a lot of D1V8s around
Regards Philip A

Thanks Guys,

I'll see if I can buy one pre-done. It'll be easier than soldering a brass "T" shut and drilling it out to 3mm. here's the plastic version on ebay by the looks of it:
http://www.ebay.com.au/itm/Crank-Cas...item4172ebc66c

seeya,
Shane L.

**DoubleChevron** · 2nd March 2015, 02:23 PM

Well I played with the brass screw on the gas mixer hose. 1/2turn has lifted the idle so it has a nice smooth, still quite low idle when hot on gas.

The side effect is a high idle when cold. With a manual gearbox this would be fine. You see the threshold values for cold idle must be different. It can try to idle as high as 1600rpm when cold .... so pulls at the torque converter that drags the revs back to about 800rpm. What this means is the idle stepper motor is happy with the cold "idling" revs of 800rpm ...

If you throw it into park or neutral at traffic lights ..... The revs shoot straight up, and within 2seconds, the idle stepper motor drags it down to a nice smooth 6->700rpm idle... Like I said, it'd be fine with a manual gearbox.

So idle stepper motors doen't work that well with automatics... as the torque converter drag can mask a "high idle". Makes sense to me....

All fun right

seeya,
Shane L.

**PhilipA** · 2nd March 2015, 02:29 PM

They are supposed to have a high idle when cold.
About 1200RPM.
Regards Philip A

**DoubleChevron** · 2nd March 2015, 03:24 PM

Originally Posted by PhilipA

They are supposed to have a high idle when cold.
About 1200RPM.
Regards Philip A

The torque converter isn't gong to allow it to get to 1200rpm without lots of dragging

Yesterday I tried, and the revs shot straight upto 1600rpm when I put in neutral. The stepper motor immediatly kicked in and pulled the revs down to about 800rpm. Which was perfect given it was warm out, and the car had been running for a few minutes.

I'd believe 1200rpm for freezing cold start in the depths of winter would be about right.

seeya,
Shane L.

**loanrangie** · 2nd March 2015, 09:01 PM

It wont drag in park or nuetral Shane.

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