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[Derek_in_Penzance]

Omega 3.0 Estate '98 mini-facelift auto with LPG
-------------------------------------------------------

My saga continues...

Having fixed the ABS, got it through the MOT etc, and enjoyed three weeks of driving around, running perfectly, the car broke down at the end of a 30-mile run up the A30 and is now stuck in a suburban road (I am getting it recovered).

Symptoms: misfiring -at first as if missing just one cylinder, then I realised it was maybe two or even three, loss of power, alarming tinkling sound from engine.

Open bonnet, find a  rubber pipe to secondary air injection solenoid valve split. Repair it with masking tape but makes no difference. Do paperclip test. It shows:

98  O2 sensor 2 circuit voltage low
38   02 sensor 1 ditto
16 Knock signal circuit 1
17 knock signal circuiit 2

and 31 -engine not running

Any ideas please? I'm assuming that something has gone wrong with the lambda circuit and the ECU is advancing the ignition, hence the tinkling sounds as engine knocks.

Symptoms are the same whether it runs on LPG or petrol. I was running on LPG at the time of the breakdown.

I'm away to the car for some hours so I can't respond to any helpful posts but if anybody can suggest anything to look for or check I'd really appreciate it. I'm fearing maybe the injection ECU has gone down but as I am a newbie to these cars I don't really know.

Thank you!
  

[Marks DTM Calib]

DIS pack failed I suspect although do check the plug wells for oil....hence you have a weak spark on two cylinders (one on each bank) which is affecting the fueling (hence the O2 sensor error codes) and causing a major miss fire.

[Derek_in_Penzance]

Thank you Marks DTM, I've just ordered another DIS pack. If it isn't the fault well, I need one anyway as a  spare, but I'm pretty sure you are probably right. I did look at five of the plugs and there was a little oil at the bottom -maybe  a teaspoonful at most -but not lots of it as I imagine can be the case.

Thanks for the help. I'll keep you posted.

[Derek_in_Penzance]

DIS pack changed for a new one. But the problem is still there. Still running as if on only 5 cylinders, pinking like mad if I drive up the road, all six plugs are black, although not oily.

So my problem is not the DIS pack after all. The fault codes are saying lambda sensors -both of them. Any further ideas?

I'm just about to jump into my Monza to go home -at least that one never lets me down! Well, not as much as my Omega so far. I think I've had about four weeks of driving it, the rest has been just one long headache!

So any help will be very welcome.

[blaee]

try to clean   all conectors,multiplugs in the engineroom.poor conection will give high or low voltage on the tech2

[feeutfo]

Thank you Marks DTM, I've just ordered another DIS pack. If it isn't the fault well, I need one anyway as a  spare, but I'm pretty sure you are probably right. I did look at five of the plugs and there was a little oil at the bottom -maybe  a teaspoonful at most -but not lots of it as I imagine can be the case.

Thanks for the help. I'll keep you posted.

Are the plug leads ok? The oil can cook the rubber at the base and allow the spark to escape, a tiny nic is all it takes. But tbh its not likely to affect that many cylinders unless youve had major cam cover leak before? Are they still original?

[Derek_in_Penzance]

Thanks for the suggestions. The car starts OK, and idles. It will drive up the road and back, with a certain amount of pinking. At idle it does seem as if it is just one cylinder that is not firing. I have looked at all the plugs; they are all black, but not oily. The leads look OK at first sight but I will check again. There is no oil to speak of in the spark plug wells. I will also check and clean as many connectors as I can find.

I am going to spend a day on this tomorrow (Sunday) and I will change leads to see whether any of them are faulty. I will also do a compression test to ensure that it is not a cylinder problem rather than ignition. I'd like to do this anyway as it will give me some idea of whether the engine in the car is basically sound. I'll clean all the connectors especially those relating to ignition and Lambda.  After that, I'll post again and let you know what has happened. Thank you for all the help.

[feeutfo]

just re read,think im right in saying lpg runs on a differant ecu to petrol so not likely to be fuel related if problem on both fuel systems. Lpg is harder to ignite than petrol so it will show any ignition problems there first.Leads to dis pack connections are correct on the new one arent they? Its very easy to get wrong. There is a guide for it. Dont ask how i know.  

[VX1]

Try testing the voltage across the lambda sensors to se if there is a fault lying there. The misfiring sounds like the leads or one of them is knackered so changing the lead may help, also both lambda sensors may need replacement as well as this can cause same symptoms as misfiring.

Paul  

[Derek_in_Penzance]

I just changed each ignition lead in turn, with no improvement. Still seemingly running on 5 cylinders. A nearly two hour job for something that on an earlier car would take minutes. Why, oh why, did they have to make access so difficult?

Maybe I'll do the compression test now, to satisfy my curiosity.

Had a look under the car the O2 sensors, can't see anything obviously wrong, and the wiring plugs are difficult to get to, so I put off doing a  voltage test. Yet another impossible-to-get-to scenario. Where do the o2 leads end up? Since both sensors are showing 38 and 98 -low voltage -that suggests a common lead or plug somewhere -any ideas?

<ponders doing a straight 6 engine conversion.... >

[Derek_in_Penzance]

OK, I think I've solved it.

Voltage test at the fuel pump relay K44 (pink one in the triangular ECU/relay box, blue/red wire that branches into three) showed 13.4 volts at idle, so I don't know what the "low 02 voltage" code was meant to show.

Anyway, look at the plug leads preparing for a compression test. Suddenly realise that the cable connector for the plug is right up inside the rubber housing. Voila! It hits me! The plugs are all suffering from a bad connection inside the plug covers, due to me carelessly pulling them off the plugs when doing my previous jobs. Two of them are even rusty and look as if they've been like that for a long time. When did I break down? When it was raining hard! The damp air always exacerbates ignition problems, especially down here in rain-sodden and mist-prone Cornwall.

OK, so I'm jumping to conclusions maybe 'coz I am excited that I may have found the obvious cause of my problems. Go away fault codes! Go back to basics and don't get blinded by science!

So watch this space. In another hour I expect to be jumping for joy with a smooth-running engine.....(please...).

[Derek_in_Penzance]

Bugger. I'm sure the leads were causing problems but that just masked the real one.

Compression readings (with Snap-on gauge):

1) 210 psi
2) 180
3) 210
4) 65
5) 215
6) 75

Cranks over quickly on the good readings, slow on the bad, with a squishing sound. Chemical test for head gasket/combustion gasses in coolant is negative. So I conclude that L/H head gasket is leaking between cylinders 4 and 6. That is really annoying, because the head gasket on that side was supposed to have been replaced only 30,000 miles ago. Obviously not very well.

The saga continues. I'm fed up with working on this car.

On reflection, maybe I'll just buy another Omega and hope my luck turns better.

<Browses eBay>.

[JamesV6CDX]

Lordy, 60/70psi in a pot is not good!

Did you have a good seal on the gauge?

[Derek_in_Penzance]

Hi, yes, I did it twice to make sure (screwing it in). Anyway, the way it runs tends to confirm it -regular lumpiness and clinking sounds from engine as if two pistons & con rods are being carried around against their will. Car starts reliably enough and manages to drive up and down the road, but 4 & 6 don't seem to be doing anything -they're just along for the ride.

But I'm no expert on these V6 engines. I am very much a learner, although I know every nut and bolt on the 12v & 24v straight six Senator & Monza engines. So if anybody can tell me my solution is simple, please do so, because I am losing the will to live. I can't face taking the head off, as I have so much paying work to do on customers' cars and my Omega really has to be be done in my (nonexistent) spare time.

[Entwood]

Before you condemn it (or do too much work) try a little old trick ... stick a desertspoonfull (about 10 cc) of lightish oil - redex used to be great for this - in the suspect pots and leave overnight, then do the compression test again. If it improves drastically you may have a sticky piston ring or two, in which case repeating the exercise 4-5 times may well free them up and restore full compression.

HTH