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[The Cambelt Kid]

Hi chaps,

I have a very quick question for you clever people...  

My V6 2.6 sounds and feels like it running lumpy, like it's on 3 or 4 pots.  It only seems to do this when re-starting the car when it's already hot and even then it's not every time.  I have a sneaky idea that the crank sensor is causing the problem but am not 100% sure.  I have scanned the OOF for crank sensor posts but i can only find ones that relate to dead non-starting cars, not a 1/2 dead one like mine.
My little orange code reader only comes up with ‘igniter circuit error’ which is because I have LPG installed, but other than that it’s clear.  No crank or cam sensor!
I would be so thankful if someone could reinforce my theory before I part with my cash.

Kind regards

[The Cambelt Kid]

Since this post I have done some investigation work of my own, which is quite difficult as I don’t want to spend any pennies.  Just me, my brain and my code reader!

I noticed that the car runs very rough at idle and I’m sure it does it through the rev range but I didn’t want to force the revs while the car was running like this.  If I blip the revs to trigger the switchover to gas the problem disappears!

Now if I stop the engine, restart and leave it ticking over on petrol the engine is rattling about all over the place and sounds rough.  If I leave it like this for about 15 seconds the EML light starts to flash, which is good news as this is all I have to go on.  So at this stage I stop the engine and read the codes as shown below:

P0300 – Random/multiple cylinder misfire.
P1300 – Ignitor circuit.
P0301 – Cylinder 1 misfire
P0303 – Cylinder 3 misfire
P0305 – Cylinder 5 misfire
P0302 – Cylinder 2 misfire
P0304 – Cylinder 4 misfire
P0306 – Cylinder 6 misfire

I know about P1300 as this is a side effect of my LPG install.  There is enough time between petrol and LPG injector switchover to trigger this.  I have had this for over a year now and has caused me no issues.

What I can’t understand is the misfires.  It misfires intermittently on petrol when warm, and rarely from cold.  The frequency has increased recently, hence my post.  But as soon as the car switches to LPG the car is fine.  I get the rattle from the noisy lifter as usual, but other that it’s fine.

My car uses a coil per plug and does not have a DIS pack.

Does anyone have any ideas on this one at all?

Regards and thanks in advance.

[Omegatoy]

sounds to me like the petrol injectors have got sticky through little use, I used to get it on mine, only thing to cure it was to use it on petrol for a while, what i did was wait till on m.way on gas about 80 lift throttle and switch to petrol and run it like that for 10miles on petrol
about once a week, any ignition fault will be far worse on gas as it requires a better spark to ignite it!!!

[The Cambelt Kid]

Ahhh that just made a bell ring in my head....

Recently i've been popping the plenum off and on like a madman.  A few weeks ago i stripped the plenum, removed the fuel supply, took out the coil per plug strips then examined the plugs.  As i didn't have any replacements at the time i put the old plugs back, they looked fine.  

Yesterday i changed the plugs for new GM ones as i thought this might be causing my petrol problems.  BUT THEN..... While changing the plugs i notice that when i came to release the pressure in the fuel rail, the pressure wasn't as high as usual.  I usually get fuel spurting all over the place and have to soak it all up with a rag, but yesterday i noticed that it was very low and very little fuel came out.  I also noticed that one of the fuel pipes connecting to the fuel rail (17mm one i think) didn't have any fuel in it!  The larger of the two had some dribbling out, but the smaller one was nearly dry!

Could this point to the fuel pump? I don’t think it could be the injectors as it’s intermittent and could be fine for days at a time.

Could it be a bad connection on the fuel pump?

I agree about the ignition theory, i had a dead set of HT leads on my 2.0 LPG Omega and running on LPG was far worse than petrol.  New HT leads fixed the problem.

Thanks
Marc

[Omegatoy]

Hmm have an idea the pump should be running all the time to keep the petrol reasonalby fresh? I know mine did, however that just made me wonder how old is the petrol in the tank? cos i have seen 3 or 4 lpg cars with a film of jellified petrol blocking the pickup filter in the tank!!

[The Cambelt Kid]

I like to burn petrol every so ofter and i put £50 in about 2 months ago.  Then i used LPG for about a month.  As lpg cars start on petrol i usually keep <30 miles worth of petrol in the tank, so maybe i have sucked up some crap and blocked the petrol filer?  This was changed before i had the car, about 25k ago.

I'll swap the filter over first as this is an easy job.

Thanks

[Derek_in_Penzance]

Fuel filters should be changed regularly. If yours was last done 25K ago it is long overdue! A clogged-up filter causes fuel starvation which will result in lumpy running. A partially dirty filter will also impair performance at higher speeds. My rule of thumb is if you don't know when the filter was last changed, and it looks dirty/corroded/generally neglected, change it!

[VXL V6]

Worth checking the fuel pump cover plate? They have a habit of corroding.

[The Cambelt Kid]

I tried again this morning and she started up fine and ticked over as smooth as ever.

Anyway i've just installed a new GM filter as i had a spare one kicking around and now have my fingers crossed for a result.  The old filter was corroded as i though (aluminium oxide??), but not too bad.  

I poured the fuel out the back of the old filter and noticed it had quite a bit of crud floating about, but the clean side of the filter looked ok.  I did try and remove the fuel plate but this was solid and i gave up in the end.  The fuel S+R pipes were not that bad, not as bad as my old W plate Omega, so no cause for concern there.

Thanks

[The Cambelt Kid]

Ah haaa, just made a breakthrough!

I put the input end of the old filter on the garden hose pipe and switched the water onto a slow trickle.  The pressure built up for a while and some dirty water/petrol dribbled out the clean side of the filter, then all of a sudden the clean water found it's way out and i had a good clean flow.

Looks like the filter was clogged up as you say...  

I don't mind having problems on the Omega, just as long as i know how to fix them!  Or know someone who does.

Thanks a million!