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[topcat]

I have same problem poor running bafflings comeing out backbox changed two middle and backbox today quieter but still poorly . I will look at those rubber pipes tomorrow

[Alex Wood]

I wouldn't have thought the secondary air injection problem would affect the running of the engine? My one-way valve failed and I had a hole blown in the hose you're talking about, and the only way I knew it was happening without lifting the bonnet was the raspberry noise when started from cold! I removed the pump and all associated pipework and plugged the rubber hoses coming off the heads. New exhaust for def and then see how it runs I reckon.

[2am Omega]

I hope this link shows a photo of the burst SAI hose in my engine bay, squeezed and crimped to reseal it.


<center>
<a href="http://s735.photobucket.com/albums/ww354/Prince2am/?action=view&current=90228OmegaElite001.jpg" target="_blank"><img src="http://i735.photobucket.com/albums/ww354/Prince2am/90228OmegaElite001.jpg" border="0" alt="Omega Elite - crimped SAI hose (90228)"></a><br /><br />
</center>

[Entwood]

Done a better link for you to show the picture .. as HTML links don't work ..

[2am Omega]

A picture tells a thousand words  

Many thanks for your help with the photo.

This really is a very helpful community !!

Thank you to everyone for your interest and assistance to guide me.

[Shagma]

I wouldn't have thought the secondary air injection problem would affect the running of the engine? My one-way valve failed and I had a hole blown in the hose you're talking about, and the only way I knew it was happening without lifting the bonnet was the raspberry noise when started from cold! I removed the pump and all associated pipework and plugged the rubber hoses coming off the heads. New exhaust for def and then see how it runs I reckon.

I removed the SAI and pipeworks also and I had no troubles after that. However, its a good advice to check the returnvalve, because otherwise I guess you will have a "fake connection" between exhaust and engine compartment, right..? correct me if I'm wrong!

[2am Omega]

I removed the SAI and pipeworks also and I had no troubles after that

Please confirm what you removed .. did that include the flying saucer shaped vacuum operated valve or the fan blower underneath, as well as the hose?

I do not feel that this SAI system is unnecessary, even after the initial few seconds after start-up. The absence of proper vacuum caused by my leaking SAI hose causes lumpy engine running and very poor fuel consumption, typically mid teens of mpg. This is improved by crimping the SAI hose to try to seal it. What do other folk think?

I have ordered a new SAI hose part 90500057 from Vauxhall.

Can someone please confirm if the Non-Return Valve is the silvery metal device shown top right in my photo. I hope this is not faulty on my car .. the part costs over £150.

What price would members expect to pay to supply and fit exhaust rear box, or complete system, and please suggest good value sources near London Heathrow area.

[Abiton]

Let's see if I can help.  
If you follow the airpath from the pump you first come to your split hose, then the vacuum operated valve, then another rubber hose which connects onto the non-return valve.

I don't understand how a split/leak where yours is bust can affect engine running, as the vacuum operated valve should be isolating that pipe once the SAI system shuts down.  

If the non-return valve were faulty, surely it would be the other hose, the one directly connected to it, that would fail??

Apologies if I've got this all backwards, I've only ever seen the 2.0 version of this system.

[2am Omega]

Got the replacement hose but not yet fitted. Different part number 93170033 in case anyone else needs one.

Chatted to the Vx Parts Manager, who came out and inspected my car .. very helpful. His opinion was that this entire SAI system could be removed .. and was in fact omitted from the facelift models. He said this burst hose was very unlikely to be the cause of my poor engine running and terrible fuel consumption.

I told him about the long lengths of blackened hair-like wadding which had spewed out of my exhaust tail pipe for several weeks, until apparently all released. Whilst it seems the rear box innerds and rusted baffles have also collapsed and been expelled, the source of the enormous quantity of hair wadding was the imploded catalytic converter(s) and this had been blasted through the exhaust system, perhaps blocking at some stage. He referred to "pre" and "post" sensors either side of the cats .. and he thought they were probably malfunctioning around the failed cat(s) causing inefficient fuel balancing, as well as increased emissions.

The problem is the cost of replacement of cats and exhaust system .. megabucks in comparison with the depressed value of an almost 12 year old 2.5 Omega with 134k miles on the clock.

Do you agree with his diagnosis? What action does anybody suggest please?

[philhoward]

It's been seen that the Mig likes an exhaust system in good order - but i've not seen a cat with wadding inside as its a honeycomb structure normally.

Also - I thought it was only the 2.6 and 3.2 V6's which had the pre- and post-cat sensors (as well as 2 cats in series on each bank)?

[2am Omega]

He said the facelift models changed from that hair-like wadding used in my 97R model to use a different honeycomb material. Yes, he said 2 in-line cats with pre and post sensors in my car. Was he mistaken?

What options are there for action?  Bite the bullet and pay the high price for a new exhaust and cats? Look for a second hand exhaust system from a scrapped car .. risks and poor quality?  Sell my car now for whatever it is worth?  Continue to drive my car and accept teens mpg?  Can you suggest other options?

Maybe wait and hope the government will follow Germany and France in paying up to £2500 to owners of older cars to persuade them to buy newish replacement cars?

What do think is best action?

[Tawfield]

I can safely say that there is no wadding in the cat boxes it has come out of the rear box,which initialy clogged up and caused your problems.
The cats are moulded ceramic with thousands of holes [honeycombe] and coated with erm precious metal, that is why they dont like being knocked about  or dropped they break just like dropping a china tea cup, I would think that if your cats are damaged, it would possibly shoot some bits out of the exhaust,they also run very hot near to red hot at times ,Id go for a cat back new exhaust,a good long burn on the motorway that should clean the crud  off the lamda sensors so that they give correct readings to the ecu for fuel rate.  

[2am Omega]

Id go for a cat back new exhaust

Please explain that exhaust.

The rear box on my exhaust is intact externally, but with innerds shot. Will that affect the engine running and fuel consumption? Necessary to be replaced?

My car has not been driven hard or fast for a long time. Max has been gentle cruise at 60 to 70 for 20 miles or so. So you are suggesting a bit of a blast to reset the lamda sensors and restore normal fuel consumption?

 

[philhoward]

Cat back - that means the centre and rear sections.  The cats are part of the downpipes, so effectively 2/3rds of the exhaust.

A good, fast run every now and then (i.e. a bit of 0-60 testing followed by a good 5-10 mile run at as much throttle as the speed limits will allow) helps to burn off the deposits which can accumulate on the Lambda sensors and cat surfaces.

I'd say that despite the externals of your exhaust are in one piece, the business bits inside are no longer doing their job properly.  This will affect the healthy running of the car - especially as the front silencer(s) are probably not much further behind their last days.

I'm guessing your car does mainly short/local runs?

Subject to confirmation from V6 owners (mine's a 4-pot) then pretty sure only 2.6 and 3.2 had the two cats, and hence 2 sensors per bank.

New exhaust time me thinks..

[Tawfield]

Your rear box is not intact is it,it has failed it may look ok outside.
A few oofers would suggest new rear box sort the faulty hose out,and take the car for a extended run,don`t have to thrash it but fast steady speed this burns the crud off the lamda sensors.
Just before Dec last year was looking for replacement car I had a 2.0ltr Estate giving 26 28 mls to a gallon one trip to Eastbourne gave a return of 32mpg the second trip was to Taunton and the car was giving a reading of 33 mpg I was`nt going slow but not thrashing the car just long stints at   70mph where poss,wonder why I got rid of the car, still the Estate I got from Taunton is a beaut can`t complain, do hope you get the car sorted.    There you go previous post confirming my answer. have to move faster on the keyboard.