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[terry paget]

So, was it a split in the old inlet?

Don't know. I looked for one and could not see one. The MAF sensor was a genuine Vx recent purchase from a  member presumed good, whereas the earlier MAFs were aftermarket and suspect. I suppose I should investigate further.  I was quite prepared to find the coil pack dodgy, or my cam cover gasket repair failing, or my new plugs (Densa) faulty or incorrectly gapped. I was warned the cracked exhaust manifold could cause faulty running. I never expected the induction tract change to cure the fault.

[terry paget]

Well done, Terry.
What's an induction tract?
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[Andy A]

Well done, Terry.
What's an induction tract?

The assembly of hoses and mass air flow meter that connects the air cleaner to the throttle box. Fitting involves 2 hose clips and one electrical connector.

Terry do you have the part number or size of the two hose clamps that connect the air flow meter?

Mine are knackered.

Glad you got it all sorted.

Thanks

Andy

S3 size 40
29-76 USA
one is labelled,
the other says NORMA 72-80
make of that what you will
The diameter of the clamp point seems to about 76mm

Correction: those are the hose clips either side of the air flow meter, not the ones I touched. The air cleaner end clip is labelled 82-92 NORMA, the throttle body end clip is labelled Norma 66-75.

Thanks Terry for the info. 

[terry paget]

Oh dear. Having repaired the cills, and sorted the stalling, I hoped this car was ready for MOT. In a short test spin, however, the EML came on. I plugged in my diagnoser, up came P0170 lean exhaust. I checked live data, and found the O2 loop was open, even with a hot engine. Both lambda sensors recorded lean, and were not switching rich-lean as they should if the O2 loop was closed.

As this thread testifies, I have changed the first lambda sensor, and the MAF sensor. Members may tell me the cracked exhaust manifold will affect matters, but I have suffered cracked exhaust manifolds before on 4 cylinder Omegas, and they have not affected emissions or brought on EMLs. Atempting to change the manifold, if I can get one, will open a whole new can of worms, so I don't want to go there.

Please advise.

[dave the builder]

How big IS the crack in the manifold ?
you could try gum gum or JBweld ,
won't last as a fix but may last long enough to prove one way or another if the crack is an issue 

[terry paget]

Good thinking.
I have a MIG welder. I was wondering if grinding a slot into the crack, and then trying to weld a repair into it, might achieve a similar temporary result. Silly idea?

[Bigron]

I'm not a welder so please don't shoot me if I'm wrong, but my understanding is that welding cast iron doesn't work: brazing does?

Ron.

[Migv6 le Frog Fan]

Cast iron can be welded Ron. 

[Bigron]

OK, lead me to the firing squad, Albs! 

Ron.

[mandula]

I've read that some have successfully welded those manifolds in-place.

Before welding drive/rev engine hot as possible so exhaust manifold is very hot, disconnect battery and then quickly weld with applicable welding method and then wrap the whole manifold with rock wool and let cool over night. This should prevent repaired manifold to crack/bend.

[Nick W]

I'm not a welder so please don't shoot me if I'm wrong, but my understanding is that welding cast iron doesn't work: brazing does?

Ron.

welding cast iron is possible, but it's a specialist job that's rarely durable on a long thin part like an exhaust manifold. Brazing tends to be a bit more successful, but the heat cycles of a manifold don't help.


Add the cost of doing it(you're not going to do it with a MIG welder for instance) and buying a new manifold is the only viable fix.

[Bigron]

Yes Nick, that's roughly the way I remember hearing it (I think from Webby the bear - where is he these days?), that welding is at best temporary if it works at all and brazing is the only answer and even that will not last forever.
Would ceramic coating work?

Ron.

[terry paget]

Thanks for all the advice, chaps. Could there be any other reason for the O2 loop remaining open? This car, and several other 4 cylinder Omegas I have owned, all had cracks in the exhaust manifolds, but passed MOT emissions tests. Repairing this car looks liable to exceed its value.
Now you see why I hate 4 cylinder Omegas.

[TheBoy]

If enough air is getting it, it will bugger up the readings, and also upset the fuelling.

[terry paget]

MOT failed. High lambda, never below 1.15, and 14 advisories. Oh dear.