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[RustyTig]

Morning all, getting to know the Omega I have just purchased and getting on top of maintenance etc - the sort of stuff that builds up with a car when it's been largely sat for the past 5 years.

One of the issues that I'm dealing with which started with a bit of hesitation between 2-3000 rpm has turned into something a bit more serious. The car will fire up and run for maybe 5-10 seconds, rev fine then proceed to slowly chunder to a halt with some rough running and eventually dying completely. It'll then start fine but repeat the above over and over.

After purchase a couple of weeks ago I put a good, new Bosch battery on it and sourced a battery clamp/tie down that was missing - it then started hesitating on start up taking several seconds of cranking to start and would then be lazy in the aforementioned 2-3000 rev range before the non-running issue started earlier this week.

I've sourced a new off-brand cam sensor because I could get one quickly and this has removed the slow start issue but not solved the cutting out after 5-10 seconds. I have a new (to me) potentiometer/pedal assembly on the way to A/B test as I've read these can be a failure point.

The last code read it threw up came back with the usual P0173 and P0170 malfunctions - it's thrown no further codes during the current non-running.

For the first 5-10 seconds of running it runs beautifully and responds to throttle inputs perfectly - until it doesn't.

I get that playing parts bingo isn't smart - but if there are some well known causes of the above symptoms to at least point me in the direction/diagnostic of, I'd appreciate it. Again - new to the world of modern Vauxhalls so don't really know the engine platform that well.

My next step is smoke/air leak test - but I can't initially hear a catastrophic enough air leak when running that would cause the car to shut off to this extent.

Input and potential ridicule always welcome.

[RustyTig]

To pre-empt what I can see is a usual follow up question I've had a look at the live data for the brief period of running (while cold - so on open loop) and I can't see any trim levels reporting for Bank 1 or 2. 0% across both while showing 0.44/0.45 volts across either.

[Nick W]

Start with the basic stuff.


Really basic:


Is what is in the fuel tank actually petrol? If it's more than a few months old, it won't be. Drain it thoroughly, flush the fuel lines to the engine, inspect the pump and change the filter before adding 20litres of fresh fuel that you bought for the purpose. At least you don't have to worry about rust with plastic tanks.


Remove and inspect the ignition system. That's both coil packs and their wiring, plus the spark plugs. If When you find water anywhere near these components, expect to replace them.


Examine the intake all the way from the air filter to the lower manifolds. You're looking for split hoses and grommets or contamination. It's German, so there's a needlessly complex vacuum system that can leak.


Don't replace any sensor or ECU until you've read its live data.

[Migv6 le Frog Fan]

As Nick says, old manky petrol has to be the first port of call. 

[RustyTig]

Petrol is fresh E5 and there's plenty of it, it's definitely not what's in the tank - could yet be delivery of said petrol, whether there's enough at prime to run faultlessly with no more then being delivered.

Thanks for the input Nick - I'll take a look at air leaks, but I've yet to come across a running issue this catastrophic and repeatable where air leak has been to blame, however I won't write it off and will dig around.

With ignition hardware I still can't see how it would run *so* well for 10 seconds then die off, I've had degradation of coil packs before and with other brands they either start or don't start.

If this was rough running I'd agree with your pointers completely - but it's very exact, repeatable dying after a set time frame of nice running.

[cam.in.head]

as nick mentions above change the fuel filter if you have not already done so .you dont mention it being done ?

[Doctor Gollum]

If you have live data, what is the ECU seeing for coolant temperature?

The ECU temp sensor is 5v and located next to the purge valve. This is 12v and the plugs are the same.

Getting these two confused results in the engine defaulting to maximum fuel enrichment. This basically dumps the injectors into the cylinders to help extreme cold starting. This is fine when the engine is cold, but will flood it in pretty short order smothering the sparks.

A poor connection in the coils wiring harness will also cause cutting out once warmed up. For diagnostic purposes, the thick brown wire to the coils IS NOT a ground.

[Nick W]

as nick mentions above change the fuel filter if you have not already done so .you dont mention it being done ?

I mentioned changing the filter if the petrol and/or tank were contaminated. Now we know that's not the case, changing the filter is unlikely to make any noticeable difference. The main failure of a fuel filter is when they're so old the casing leaks


Less basic checks:


measure the fuel pressure from ignition on through running rough to finally stalling.


that combined with a check of the fuel flow rate will prove the fuel pump.


The ignition checks I suggested are still valid, as water in the plug wells is a common fault.


A thorough inspection of the engine loom and the various earth points.


Some way of checking the injector spray pattern would be useful.

[RustyTig]

Thanks Nick, I’m agreeing more and more with you on fuel delivery checks.

I’ll see what data I can get in terms of fuel rate while it’s running.

I’ve chucked another 20l of E5 in there and it ran noticeably longer than before, like 30seconds instead of 10 - I’m tempted to whip the in-tank pump out (presuming there is one there) and double check what’s going on in there along with your other suggestions.

Is anyone aware of any funky relay on these that controls some kind of cat warm up cycle when cold that then switches? The cut off is just ‘too’ perfectly timed to not be suspicious for me.

Will report back once I’ve done some more fiddling.

God I’m loving being back in retro cars again 

[RustyTig]

Just saw your post Doctor G - another great shout, will take a look what’s going on there too.

It definitely feels like it’s running on some kind of enrichment mode and then not switching over thus flooding/killing the spark.

[biggriffin]

Have you had any of the Vacuum pipes off, or removed the intake and replaced the vacuum pipes wrong or the plug on the back of the plenums..

[YZ250]

…………
The last code read it threw up came back with the usual P0173 and P0170 malfunctions - it's thrown no further codes during the current non-running.

For the first 5-10 seconds of running it runs beautifully and responds to throttle inputs perfectly - until it doesn't.
……………

Could the fuel trim codes be a red herring thrown by a dodgy crank position sensor.    I seem to recall somebody on here parking up their V6 for several months when it was working fine and when it was put back on the road it suffered similar issues and it turned out to be the crank sensor. When my CPS have failed in the past, the engine has died when it’s hot and starts fine when cold, OR on one of mine it simply wouldn’t start at all. If the CPS is failing, the crank wouldn’t know where it was so the communication with the ignition and fuel would be lost.
The pattern doesn’t fit all of your symptoms but as it runs fine for an albeit brief amount of time I thought it might be worth checking out. 

[RustyTig]

Have you had any of the Vacuum pipes off, or removed the intake and replaced the vacuum pipes wrong or the plug on the back of the plenums..

No, none of these have been touched since I bought the car and it was running (with aforementioned hesitation issues)

[Doctor Gollum]

Could be why it was sold...

[johnnydog]

Could be why it was sold...

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