astra van 1.6 8v petrol/lpg misfire

[williev]

hi all new to the forum. i have just purchased an astra van lpg for my work and econemy. when i got it it was running rough and sometimes cutting out mostly when coming to lights and roundabouts i had a look about and couldnt find anything untoward. since the first day of having it i have found that in the morning from cold if runs fine till warmed up then starts its cutting out. last night i had a look at the petrol loom and found a few striped wires none of which were toutching each other so i taped up put it back together and seemed to run fine so then i tried to switch to lpg and it switched over nearly cut out and ran on 3 cylinders and trying to rev engine is near impossible. i have switched back and fourth between the 2 and have found that sometimes when it misfires(4th cylinder) when you put it back to petrol the mis fire is still there (7/10 times) but if you turn off, remove the key wait a minute then switch engine back on the misfire is gone.
i have inspected lpg loom and connections and there doesnt seem to be any broken striped cables. any help in the right direction would be greatly appreciated. PS have briefly applied 12v to cylinder 4 lpg injector and it clicks as if working and loosened feed pipe and gas came out so all would seem to be fine there

[rossko]

Is there some reason you wouldn't begin with the favourite problem area for any Astra, spark plugs and coil pack?

Check that you have a "factory fit" Necam system, not all Astra are.

[williev]

hi sorry forgot to mention coil pack replaced by previous owner not long ago i did spark plugs on tues old ones looked rough but still runs the same on new ones getting good spark at each plug. its a factory fitted system with the electronic injectors i believe

[williev]

also speedo isnt working any idea where the sensor is? im pretty sure its on the gearbox just dont know where abouts

[williev]

and just found out by looking on the auto gas website that i have the necam teleflex SGI injectors, if that helps anyone

[lpgnewbbie]

If your getting it on both fuels its most likely parts used by both systems, so coil, plugs, petrol ECU and compression
If you have a short in the petrol ECU injector pulse line to the LPG ecu then on both fuels it will not be happy as on petrol it will misfire if injector pulses are lost and on lpg those pulses will still be lost and lpg will misfire.

Check compression, after that you will have to tap into the injector pulse for each cylinder. How you do that is up to you.

[williev]

yeah but on first startup petrol is fine then if switched over to lpg it misfires on cyl no 4 and if left on lpg for a bit, when switched back to petrol the misfire is there on same cylinder and the only way to cure it is to switch ignition off then switch back on and hey presto misfire gone

[rossko]

So find out if your no.4 gas injector does anything - mechanics stethoscope is useful.

[williev]

just tried injector outof its seat but still connected to gas line tapped 12v to it briefly several times and no sign of anything happening so im guessing that because the LPG injector is faulty its telling ecu not to fire on petrol cos theres somethin up with cyl 4.
so with that sussed i need a replacement injector and also need to get the speedo sorted out but cannot seem to find it on the gearbox and its still cutting out at idle when coming to lights roundabout etc but when started from cold its fine for about 10 mins, any ideas?

[rossko]

What can happen is that the engine management can detect a badly misfiring cylinder, whatever the reason for the misfire. The engine management then shuts that cylinder down. No amount of fuel switching will recover it, until you stop-start the engine again.

You need to decide if "running fine for the first ten minutes" really means it runs fine on petrol only. Something that may help you is to actually drive it around on petrol, since you think the gas system is broke, and see if you still get this stalling thing. It is difficult to decode what it's running on at the time of your complaints.

People on Astra forums are more likely to have some idea about speedos than people on general LPG forums.

[gazza345]

the speedo runs off the l/h abs wheel speed sensor(nearly 100% sure its the l/h one but may be the r/h one), do you have an abs light on?? possibly a faulty sensor or poor connection at the joint in the wire behind the splashguard

[williev]

hi rossko thanks for that ive been drivin around a lot on petrol for the last week did an 80 mile trip on petrol alone and it was fine didnt even cut out on idle even on the way back was ok idle problem returned but ran fine none the less if it cut out just had to fire it up and away it went
and gazza thanks as well found speed sensor on passengers front wheel and the problem is obvious, the two wires that go to the sensor are taped up so new sensor needed there and i believe a new hub is required here

[rossko]

hi rossko thanks for that ive been drivin around a lot on petrol for the last week did an 80 mile trip on petrol alone and it was fine didnt even cut out on idle even on the way back was ok idle problem returned but ran fine none the less if it cut out just had to fire it up and away it went

I still got no idea if you mean the "idle problem" occurs on petrol or not
Throttle body drillings get gunged up on these cars, don't they?

[williev]

just petrol havent switched lpg on when im driving except the first day i had it and then only when in the drive trying to source the lpg misfire. as for the gunking in throtte body i didnt know this happened we have had a lot of vauxhalls from corsa to calibra and most in between except of course an astra so thanks i will check for this in the throttle body tomorrow.
the cutting out is difficult to pinpoint sometimes it cuts out sometimes drops to 200rpm then catches itself and idles back at about 600rpm and sometimes will drive some distance and not cut out but it only cuts out when clutching to change gears or stopping at a roundabout/trafficlights, sometimes now that im used to it i can press accelerator to keep it at 5/600rpm and then it will hold itself but sometimes it will keep trying to cutout no matter how much i try to coax it if i let off accelerator it will die but if started back up will almost always idle fine. but never cuts out when driving with the revs above700rpm or more.
hope this is enough info for you and not too confusing i know in my head what its doin but find it difficult to put into words others will understand, thanks

[Gilbertd]

Sounds like a sticky idle control valve to me. Or the drilling that the ICV is connected to is gunged up. Sounds like a good strip down and dowsing with carb cleaner is called for.

[williev]

the idle control valve sit on top of the manifold doesnt it? ive cleaned this up with carb cleaner but seems not to have worked possably a new one? had this feeling myself just wanted other peoples thoughts before i started throwing money at parts cos theyre not cheap incase mayb there was other things that could cause this that ive overlooked

[williev]

well turns out the rough idle and cutting out was caused by the speed sensor not workin on the front passengers wheel which was worn away because someone put a driveshaft with an abs ring on and didnt see that it was jammed agenst the sensor so now runs fine with speedo working just tryin to source an LPG injector code 003-3 if anyone knows of one or has one for sale

[williev]

just got a new lpg injector today and fitted it, works great, but comes with a new issue. now another injector is givin bother no2, went through the process of swapping from 2-3 then swapping pipes etc and the fault moves with the injector so has any one any for sale or know who sells them cheapest any info would be helpful

[rossko]

There are real reasons for the advice "change injectors as a set" (given for petrol or gas), it's not just sales blurb. But costs are prohibitive.

I am casting around myself for an economical way to do that, and haven't come up with one yet.

[williev]

well a set of four from vauxhall are about a grand as you prob know. autogas sell for £581 a set but dont say what ser number they are. the one i got on sat was new and was only £70 he has a garage and had it left over from a set where he had 2 vans in, 1 van needed 1 and the other needed 2, so he managed to get away with replacing as singles.
i can buy as singles for £125 each so even if i need another 3 the set will have cost £445 saving £136 on autogas price so its cheaper and i can see if i can get away with replacing another one but possably not but finding people who sell them is proving difficult