LPG Overrun/Stalling Problems

Hi everyone, been viewing this forum for quite a while now so thought i would make an appearance!

Ive got a really annoying problem with my 96 4.0 SE auto p38 with romano RISN LPG system; for a few months now it has developed a habit of stalling when coming to a stop or slowing down for a junction, it only does this on lpg, on petrol its never stalled on me at all.

It also runs really rough on gas on overrun (not sure if thats the correct term?), when im going downhill or when im not accelerating it doesn't respond when i press the throttle, i can press the pedal a good few cm before it responds, when it does respond it shunts/lurches badly to pick back up.
Other than that it pulls really well on gas and is great on motorways.
have managed to live with the problem so far, when approaching roundabouts I've learnt to switch over to petrol!

So far tried various things, new stepper motor(IAC) was the main suspect, heard lots of problems with stalling because of these, new set of spark plugs, new crank sensor, air filter, MAF cleaned and tested, new lpg filter - no change.
Got it plugged into an autologic and i went through checking all the sensors, lambdas are both good, MAF etc. No fault codes either?

Bought a Romano diagnostic cable and software set for the LPG all the readings look good, tried doing an auto calibration of the system, stalling problem got a bit better but was really lacking in power struggled to reach 50mph!
Decided to put the old settings back on, checking the manual carb settings they all seem to be at +25? must have been done by the previous owner.
Im guessing this might be the issue, but i dont really have a clue how to set this up properly or if this has anything to do with it.

Sorry for the extreme detail, the problems driving me mental!
just wondering if anyone else out there has experienced this,

Many Thanks

I would have a look at the gas pressure. Vaporiser diaphrams stretch over time and reduce the output pressure. Not sure what your system should be but my Alesi N on my 4.6 is 1.4 BAR. You should be able to check this with your software and make adjustments on the vaporiser by screwing in the adjustment screw in the middle of the vap. to up it a little, make sure you reaserch the correct pressure first.

Thanks for the quick reply, just had a check of the pressure and its showing some worrying values.
On idle after switchover its at 0.7 bar?! after a minuite or so it moved up to 1.7bar, fluctuating between 1 and 3.9bar as i changed the revs, is this normal?
Been struggleing to find the correct pressure for my system, but my values seem a bit extreme?
The only bolt i can find on the vaporiser in the centre is about 10mm and its stuck solid, not sure its an adjustment bolt?
Just uploaded some screenshots not sure if all the settings are right?









Thanks again

The software your using is the same as mine so I am going to summise the ECUs are the same so its fair to say that your gas pressure should be the same at 1.4 bar. This should be reasonably static perhaps dropping a little under heavy acceleration. Definatly not swinging about as much as you say. I am going to suggest you have a look over at this forum, there are a couple of good guys on there who will give you a better answer than I can, the likes of Rossko and Andyvee are both top fellas, if they give you advice, listen.

Sounds to me as though your vaporiser is shagged. let us know how you get on.

Hope this has helped, and if it has I may ask for a return favour with some Solidworks questions

were did you get hold of the leads and software for your system and how much

Re: LPG Overrun/Stalling Problems
The software your using is the same as mine so I am going to summise the ECUs are the same so its fair to say that your gas pressure should be the same at 1.4 bar. This should be reasonably static perhaps dropping a little under heavy acceleration. Definatly not swinging about as much as you say. I am going to suggest you have a look over at this forum, there are a couple of good guys on there who will give you a better answer than I can, the likes of Rossko and Andyvee are both top fellas, if they give you advice, listen.

Sounds to me as though your vaporiser is shagged. let us know how you get on.

Hope this has helped, and if it has I may ask for a return favour with some Solidworks questions

Click to expand...

Thanks for the link, looks a great forum, will get posting
To be fair i think your right about the vaporiser, a few months ago the system went through a habit of blowing off the main injector feed hoses! a clear sign i think that it isnt right!
Have heard nothing but trouble about the romano systems, so is to be expected

Cheers for the suggestion, wouldnt have looked into the pressures otherwise,
Yeah please question away with the solidworks, its the least i can do ill try my best to help. PM probably best.

Big vee Re: LPG Overrun/Stalling Problems
were did you get hold of the leads and software for your system and how much

Click to expand...

Ebay seller, allways got several kits, for RIS & RISN. Does loads of other system kits as well. Really quick delivery too.
Romano LPG Interface

Also check your ignition system...
LPG is harder to ignite.
Had similar problems with the 101, new plugs and leads, and all was well...