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PostPosted: Thu Jul 07, 2016 12:01 am 
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I have a 2006 Astra 1.6 with a BRC Fly Sequent System fitted.

Whilst out last night got in car and drove down the road and it started misfiring and the EML came on. Doing the Pedal Test Trick and using my code reader it came up with P0304 Misfire Cylinder 4. First thing I suspected was the Coilpack so changed that but it still did the same.

However, when I switched it back to Petrol it runs fine with no Misfire, back on to LPG and the Misfire comes back. So I'm thinking number 4 LPG Injector has had it or on its way out. Do you think this is what it may be?

It is fitted with BRC Orange Injectors.

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PostPosted: Thu Jul 07, 2016 2:24 am 
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When did it last have a new set of plugs? Often a fault will appear when you are running on gas and not appear on petrol so the assumption is that it has to be the gas system - this isn't always the case though!

Because LPG is harder to ignite than petrol, the plugs have to work harder so tend to have a shorter service life than normal. On a "normal" 4-pot engine like the Astra with easily accessed plugs, the chances are it will be cheaper to buy standard plugs and replace them more often with only the inconvenience of actually changing them to worry about.
On something like a FWD V6 with the rear bank close to the bulkhead and the plugs buried on the side of the head rather than the top, maybe fitting standard plugs more often isn't such a great idea! :wink: :lol:

Recently i had a Lambda sensor go and i could make it happen every time, without fail, running on gas giving it some beans. It had to be a gas problem bringing the MIL on, right? Wrong!

I switched to petrol and reset the ECU, gave it the beans and got a red herring - it didn't bring the MIL light up! :?

So i gave it a few more beans and lo & behold the MIL popped up like a little red monster!. Reset the ECU and gave it a similar amount of beans, MIL back on again.

Checked the ECU - 2 flashes - rear bank Lambda sensor. :shock: :( It had a new pair of sensors (front and rear banks) about 2 months ago for the MoT as one of the original sensors (front) failed during the emissions test.

The point of all this waffle about Lambda sensors is don't discount something just because it is new/recently fitted and often the fault is there on petrol as well, just needs slightly different conditions (like me giving it a few more beans to get the Lambda to play up) to show itself.

If your Astra had a set of plugs recently, what make were they, is the gap correct and if you move the plug from the cylinder with the fault does the fault move to the new cylinder?
Most people go for NGK or Bosch plugs as they tend to be the most reliable - personally it's NGK as 1st, 2nd, 3rd and 4th choice for me with Bosch coming a close 5th. :wink: :D

Could well be worth throwing a new set of NGK plugs at it, especially if you're unsure when the plugs were last changed - it won't do any harm and will eliminate one of the most obvious causes.

Let us know how you get on!

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PostPosted: Thu Jul 07, 2016 8:40 am 
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LairdScooby wrote:
When did it last have a new set of plugs? Often a fault will appear when you are running on gas and not appear on petrol so the assumption is that it has to be the gas system - this isn't always the case though!

Because LPG is harder to ignite than petrol, the plugs have to work harder so tend to have a shorter service life than normal. On a "normal" 4-pot engine like the Astra with easily accessed plugs, the chances are it will be cheaper to buy standard plugs and replace them more often with only the inconvenience of actually changing them to worry about.
On something like a FWD V6 with the rear bank close to the bulkhead and the plugs buried on the side of the head rather than the top, maybe fitting standard plugs more often isn't such a great idea! :wink: :lol:

Recently i had a Lambda sensor go and i could make it happen every time, without fail, running on gas giving it some beans. It had to be a gas problem bringing the MIL on, right? Wrong!

I switched to petrol and reset the ECU, gave it the beans and got a red herring - it didn't bring the MIL light up! :?

So i gave it a few more beans and lo & behold the MIL popped up like a little red monster!. Reset the ECU and gave it a similar amount of beans, MIL back on again.

Checked the ECU - 2 flashes - rear bank Lambda sensor. :shock: :( It had a new pair of sensors (front and rear banks) about 2 months ago for the MoT as one of the original sensors (front) failed during the emissions test.

The point of all this waffle about Lambda sensors is don't discount something just because it is new/recently fitted and often the fault is there on petrol as well, just needs slightly different conditions (like me giving it a few more beans to get the Lambda to play up) to show itself.

If your Astra had a set of plugs recently, what make were they, is the gap correct and if you move the plug from the cylinder with the fault does the fault move to the new cylinder?
Most people go for NGK or Bosch plugs as they tend to be the most reliable - personally it's NGK as 1st, 2nd, 3rd and 4th choice for me with Bosch coming a close 5th. :wink: :D

Could well be worth throwing a new set of NGK plugs at it, especially if you're unsure when the plugs were last changed - it won't do any harm and will eliminate one of the most obvious causes.

Let us know how you get on!


Thanks for your reply. It had a new set of NGK Plugs about 4 weeks ago which I fitted myself and are gaped correctly. It also had a new rear Lambda Sensor about 6 weeks ago. It has done about 210,000 miles on these injectors as I had it converted so know when it was done and how many miles it has done since then.


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PostPosted: Thu Jul 07, 2016 9:33 am 
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While I would usually agree NGK plugs are best, some of the Vauxhall engines are an exception and best results by far come from fitting the Bosch plugs recommended by Vauxhall for those models. In fact, such engines can struggle to run well on any other plug I've tried, including NGK. Usually if there is a single electrode option for plugs for the engine model it will give best results on LPG but the Bosch plugs I refer to are twin electrode..

Check what recommended (by Vauxhall) plugs are - but it is looking 50/50 between plugs and orange injector at the moment.

Simon

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PostPosted: Thu Jul 07, 2016 10:29 am 
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LPGC wrote:
While I would usually agree NGK plugs are best, some of the Vauxhall engines are an exception and best results by far come from fitting the Bosch plugs recommended by Vauxhall for those models. In fact, such engines can struggle to run well on any other plug I've tried, including NGK. Usually if there is a single electrode option for plugs for the engine model it will give best results on LPG but the Bosch plugs I refer to are twin electrode..

Check what recommended (by Vauxhall) plugs are - but it is looking 50/50 between plugs and orange injector at the moment.

Simon

Thanks for the reply. Mine has the Z16XEP Twinport Engine which uses single electrode plugs. Not long before I changed the plugs I did once get a misfire on Cylinder 4, stopped the car, cleared the code and it didn't do it again. However, it was then I decided to change the plugs. The ones I took out were the GM Bosch ones but decided to replace them with the NGK after reading several posts on here that NGK were better. Does sound like the Injector then.

Are they easy enough to change? Photo below is my Injector rail. On the other side of it is a nut holding it in place do I just disconnect the pipe, undo the nut and push the Injector through the block?

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PostPosted: Thu Jul 07, 2016 10:52 am 
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smokie1010 wrote:
Are they easy enough to change? Photo below is my Injector rail. On the other side of it is a nut holding it in place do I just disconnect the pipe, undo the nut and push the Injector through the block?
Yes, with this type of BRC injector that's pretty much it, easy.

To confirm the injector problem you could swap the position of 2 of the injectors (including number 4 of course) to see if the misfire moves with the injector.. Need not even move the injectors, could just swap the pipes and electrical connections around.

If the fault doesn't move with the injector I'd be doing a compression check next, followed by swapping petrol injectors around to check for a leaky injector on cyl 4.

I have various BRC injectors lying around, screw type, circlip type, different colours, etc. Not sure if I have an orange screw in type but I suppose you might as well buy new.

Simon

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PostPosted: Thu Jul 07, 2016 11:26 am 
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LPGC wrote:
smokie1010 wrote:
Are they easy enough to change? Photo below is my Injector rail. On the other side of it is a nut holding it in place do I just disconnect the pipe, undo the nut and push the Injector through the block?
Yes, with this type of BRC injector that's pretty much it, easy.

To confirm the injector problem you could swap the position of 2 of the injectors (including number 4 of course) to see if the misfire moves with the injector.. Need not even move the injectors, could just swap the pipes and electrical connections around.

If the fault doesn't move with the injector I'd be doing a compression check next, followed by swapping petrol injectors around to check for a leaky injector on cyl 4.

I have various BRC injectors lying around, screw type, circlip type, different colours, etc. Not sure if I have an orange screw in type but I suppose you might as well buy new.

Simon

Update. Went out to car and was checking the wiring etc and decided to check the 2 fuses in the LPG wiring loom and were ok. Next to it in the LPG wiring loom is a relay, I had a spare relay so changed it, more out of hope more than anything. Started car and when it switched to LPG no misfire. Put the old relay back in and as soon as it changed to LPG it died. So put the spare relay back in, no misfire and then took the car for a run and its now running okay on LPG.

It seems a bit bizarre as I thought that relay was for the solenoids but I could be wrong. Although if it is it might have been on its way out and wasn't letting enough current through to completely activate the solenoids and there wasn't enough pressure but I'm just guessing now. Does seem a bit strange that changing the relay seems to have sorted it, well for now anyway.
.


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PostPosted: Thu Jul 07, 2016 10:53 pm 
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Very odd about the relay - if you hadn't refitted the original and proved the point i would have queried it but it seems a very odd fault fixed by hope! :wink: :lol:

Joking aside, if it comes back, try swapping the injectors round as Simon suggests or change to Bosch plugs - i'd totally forgotten about the Vauxhall thing about not running any plugs except Bosch in some engines. :oops: Shouldn't have done, had enough Vauxhalls in my time! :lol:

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PostPosted: Fri Jul 08, 2016 2:28 pm 
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Possible to get situations where, if an install should switch back to petrol due to low pressure etc, in cases where the low pressure situation is caused by a faulty solenoid (or feed to solenoid) then instead of a switch back to petrol the engine will die - due to too sudden a drop in pressure. But causing a misfire only on a certain cylinder is unusual!

I too would think the relay is for solenoids but could check if it's for the full system by seeing if the switch inside still light up with the relay removed. A voltage drop to the ECU could cause such problem.

Simon

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http://www.Lpgc.co.uk
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07816237240


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