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[x1xv45]

This continues from previous post: http://www.omegaowners.com/forum/index.php?topic=115692.0
Since then I've replaced cam and crank sensor (with known good ones from RobG), and re-cleaned throttle body with new gasket, re-checked all breathers (fine), re-checked spark plug wells for any oil or water (fine), and checked for vac leaks with carb cleaner, but couldn't find any, replaced fuel filter. The problems continue as before - very rough, really terrible at ignition, have to repeat 4 or 5 times, then starts to smooth out, then it's fine and runs great until the car sits for a few hours. Don't know what to do now.

[terry paget]

Hi FrankH. I am following your  threads with interest, having a 2.2 behaving similarly, if less frequently.

Could it be the ECU failing? I have had one fail on a Senator, used to keep spares handy, but never read mention of ECU failure on this forum. They are full of soldered connections, which tend to crack and become intermittent with aging and vibration. Are they completely infallible on Omegas?

[x1xv45]

Interesting idea, but it needs someone with much more experience than me to comment on it. It's nice to know someone is interested out there - I'm getting over a bit of post-crank sensor depression: after hours of bloody struggle, the satisfaction of getting it done, and then absolutely zero result!

[RobG]

Tim, have you tried with MAF disconnected on initial start up

[terry paget]

On the Senator I could test by substition. I had 2 explod 24 valve 3 litre cars, one would not start, so I switched ECUs, and the fault switched with it. Not so easy on Omegas, with immobilisers. I wonder if it can be done by the owner driver?

My sympathy about changing the crank sensor and it not curing the fault. It's the one job that is easier on the V6 Omegas than on the straight fours. Also with changing all the bits you have changed and still having the fault. Don't despair, I am sure this forum will crack it in the end.

[terry paget]

Idle thought. If I switched the ECUs between two similar Omega, and transferred the immobiliser chips between keys, would they start?

[x1xv45]

Tim, have you tried with MAF disconnected on initial start up

- just tried it: same prob, took two tries to get it running; you might say that's an improvement, but the number of tries is pretty random - I'll try again in a few hours though.

[cem_devecioglu]

Idle thought. If I switched the ECUs between two similar Omega, and transferred the immobiliser chips between keys, would they start?

you will need the immo ring around the keyhole on the steering..

[cem_devecioglu]

and as for the rough running, I have seen lots of omegas lke that.. unfortunately their problems were not as simple as sensors alone

leaky exhaust, condition of valves + stem seals, injectors , lamnbda sensors , pistons rings all effect in combination..  ecu is the simplest to try..

[x1xv45]

and as for the rough running, I have seen lots of omegas lke that.. unfortunately their problems were not as simple as sensors alone

leaky exhaust, condition of valves + stem seals, injectors , lamnbda sensors , pistons rings all effect in combination..  ecu is the simplest to try..

I take your point, but the issue is mainly rough "starting", not running, once it's got started it smoothes out, and seems normal to me. Wouldn't all those things be noticeable all the time, not just at startup?

[cem_devecioglu]

and as for the rough running, I have seen lots of omegas lke that.. unfortunately their problems were not as simple as sensors alone

leaky exhaust, condition of valves + stem seals, injectors , lamnbda sensors , pistons rings all effect in combination..  ecu is the simplest to try..

I take your point, but the issue is mainly rough "starting", not running, once it's got started it smoothes out, and seems normal to me. Wouldn't all those things be noticeable all the time, not just at startup?

after engine warms up , clearences become smaller so you wont feel it.. however,  imo so many parts can cause rough starting so you still need to  control a long checklist

[terry paget]

and as for the rough running, I have seen lots of omegas lke that.. unfortunately their problems were not as simple as sensors alone

leaky exhaust, condition of valves + stem seals, injectors , lambda sensors , pistons rings all effect in combination..  ecu is the simplest to try..

What's the mileage, Frank? I appreciate all the above can affect the running, but I have cars that have covered 200,000 plus miles still showing no sings of worn rings, valves, etc. They seem to last forever on modern cars. Not lambda sensors I grant.

My 2.2 is low (80,000) mileage and runs perfectly once warm and most of the time when cold.

[PhilRich]

Hi again Frank, sorry you're still having problems
Harking back to my input on your previous thread, I took it as read that you'd physically checked your rubber plug covers for splits/ bits missing  and given the coil pack a close going over with your Mk.1 eyeball for minute cracks in the body (looks like 'marbling')
Both the above, if present cause a loss of spark power to the plug electrode, hence poor starting/idling, so if not already checked then worth doing now perhaps . 

[x1xv45]

and as for the rough running, I have seen lots of omegas lke that.. unfortunately their problems were not as simple as sensors alone

leaky exhaust, condition of valves + stem seals, injectors , lamnbda sensors , pistons rings all effect in combination..  ecu is the simplest to try..

I take your point, but the issue is mainly rough "starting", not running, once it's got started it smoothes out, and seems normal to me. Wouldn't all those things be noticeable all the time, not just at startup?

after engine warms up , clearences become smaller so you wont feel it.. however,  imo so many parts can cause rough starting so you still need to  control a long checklist

cem: Makes sense. The only thing on your list that I could contemplate is the lamba sensor, but I've put it off because i wouldn't know how to deal with stripped threads on the downpipe, plus the £165 cost, the other things are beyond me and probably my wallet.
[/quote]What's the mileage, Frank? I appreciate all the above can affect the running, but I have cars that have covered 200,000 plus miles still showing no sings of worn rings, valves, etc. They seem to last forever on modern cars. Not lambda sensors I grant.

My 2.2 is low (80,000) mileage and runs perfectly once warm and most of the time when cold.
[/quote] terry: Mine has 89000 miles, lots of oil changes and looking after breathers. It has to endure mostly short journeys, and occasional blasts down to London and back, which is probably not great for it.

Hi again Frank, sorry you're still having problems
Harking back to my input on your previous thread, I took it as read that you'd physically checked your rubber plug covers for splits/ bits missing  and given the coil pack a close going over with your Mk.1 eyeball for minute cracks in the body (looks like 'marbling')
Both the above, if present cause a loss of spark power to the plug electrode, hence poor starting/idling, so if not already checked then worth doing now perhaps . 

PhilRich: It all looked good to me, but now I know what to look for, I'll grab my reading glasses and make a better inspection - back in a bit...

[x1xv45]

Hi again Frank, sorry you're still having problems
Harking back to my input on your previous thread, I took it as read that you'd physically checked your rubber plug covers for splits/ bits missing  and given the coil pack a close going over with your Mk.1 eyeball for minute cracks in the body (looks like 'marbling')
Both the above, if present cause a loss of spark power to the plug electrode, hence poor starting/idling, so if not already checked then worth doing now perhaps . 

Really, it all looks like new. Earlier today I also checked the plugs themselves, in case there was some fouling, but they look dry and good, and they're GM, I put in a year ago.