v40 bi-fuel tick over probs

[aaron forsyth]

I bought an 02 v40 bi-fuel last week off a friend, it was owned by his late father and hasn't seen a lot of use other than short trips round edinburgh. I think that it was sorned prior to being on the road this year, and as far as I know has been regularly serviced. It has only clocked 52k and looked good and ran [in the driveway] with no probs. My suspicions where first raised as I proudly reversed my new car out of the drive and the tick over began varying in speed, i passed it of as a glitch and continued using it with no problems for several days. I filled the gas tank as it was running empty, drove five miles and parked up. Some hours later went to start the car and it refused to tick over on either fuel, accompanied by the engine management light. Diagnostics [from a friends hand held reader] showed a faulty air mass sensor [£39.00 from Autosensors, ebay, as opposed to £260 from factor or dealer] and cam shaft position sensor £37 from dealer. Having fitted the parts and clearing the codes there was no improvement whatsoever, management light still on, and more codes to read- 'circuit low input' 'p0131 02 sensor circuit' & 'low voltage [bank1 sensor1]'.
It reminds me of my epson printer that will tell you that it needs black ink but once changed then it needs yellow and so on till i've changed all
cartridges!
As it is drivable and runs well over 1000 revs, I decided to take it around 300 miles north to the highlands hoping that it just needed a a bit of a thrashing to clear it out and burn of any residual deposits in exhaust etc. It has improved a bit in performance, other than tick over but now switches itself from gas to petrol especially after long downhill engine braking. I have been clearing the codes and re-reading them as there is a bit of inconsistency of what shows up, sometimes telling me I need a new air mass meter that has already been changed.
Having read up from your learned selves on this site, I have learned that spark plugs are an issue, I shall have a look at them tomorrow, and it looks like the gas system is due a clean as it is showing lack of power on gas, especially at low revs, similar to some of you other members.
I am reluctant to keep throwing sensors at it that may or may not make a difference.
Is there something electronic that controls the tick over?

I took volvos as being reliable, are these cars just a maintenance nightmare or have I bought a lemon?
I won't rush out to buy a pair of jumbo cords and some beige brushed suede shoes just yet but hope to give the car a second chance.
Any advice?

Thanks
aaron

[Joe Harding]

I can only speak from experience of a much simpler system I installed on my 340.
Yes, at low engine revs, the gas is a weak mixture to ignite - much weaker than petrol. It will stumble. Check spark plugs, HT leads and anything in between you and a good fat spark.

I have a distributor on mine. Replacing that went some of the way to improving things. The rest was accomplished by valve settings.
Also check no air entering the system along the way.

Have fun.

[aaron forsyth]

Thanks for that, any pointers are a help. I have had the plugs out and have given them a good scrub up with petrol and a bronze brush, they are the triple point ones which don't seem to carry much cred on this site, so they will get changed when I am back in the city. The annoying thing is, the car works fine on gas and petrol but stalls at tick over on both fuels.
Anyhow, I have given in and booked it in with Stenhouse motors in Edinburgh as they know their LPG and the volvo V40 and as the car is still bristling with engine management codes that are beyond me, I am hoping they will say "oh I know what that is". I assume that they will also check gas pressures etc. I rarely visit a garage but so long as they wave their magic wand then I don't mind parting with a few quid.

[Joe Harding]

Rough idle on both fuels, well that narrows it considerably. The only common features are ignition and air. Do you have a distributor? Having checked that, look for air ingress into the system somewhere.

[classicswede]

It could be a lot of things.

I would start with reading the OBD codes clearing them and then running the engine and see what comes back up. There would be some good clues as to what the problem is from the codes.

Air leaks is a basic thing you can check for by spraying carb cleaner or Lynx around teh air intake system. If leaking air if will suck in the fuel and change the engine note.

Looking at the codes I would suggest running some forte injetor cleaner through as the petrol will have gone stale and turned into jelly. That would cause the lean running you are getting.

After doing that a good fill up of fresh petrol would help. Getting it running right on petrol before considering using the LPG