Failed MOT on emissions

[Laird Scooby]

Originally Posted by besidetheseaside

Car is 1993, I will clean up the PCV system over Easter and order some leads, I did replace them a few years ago but at £24 a set at ECP they are worth a go. I have noticed s smelly exhaust so am even considering putting a cat on.

It doesn't have a cat? Or do you mean you've de-catted it?

If it's the B200F from the factory then it should have the cat, if it's never had a cat then it shold have passed on those levels as it would be eligible for the BET - Basic Emissions Test.

In fact, it may still be eligible for that, get the tester to check the system as sometimes cars slip through on the cat test that are eligible for the BET or to be more exact, they're not tested on the BET when they could be but still pass the emissions.

Either way, most likely cause is going to be blocked PCV/breather system and if it is running rich, the slight misfire every so often is the ECU sending the mixture lean because it has crept up - nothing to worry about usually.

[classicswede]

He aready said the cat was replaced about 2 years ago.


It should be able to pass without the cat there, the smell is likely where it running rich. Did you fit a good correct fitting lambda sensor or a cheap universal job?

[Laird Scooby]

Originally Posted by classicswede

He aready said the cat was replaced about 2 years ago.


It should be able to pass without the cat there, the smell is likely where it running rich. Did you fit a good correct fitting lambda sensor or a cheap universal job?

Hence me quoting what he said about putting a cat on it!

My money is on a blocked PCV system and possibly that the cataclean or Forte or whatever it was needs a little more time to work.

[bob12]

Originally Posted by besidetheseaside

Car is 1993, I will clean up the PCV system over Easter and order some leads, I did replace them a few years ago but at £24 a set at ECP they are worth a go. I have noticed s smelly exhaust so am even considering putting a cat on.

Oh .. no cat!! Where did that go?

You won't regret the ecp plug leads, especially on big discount times .... I have used them for years (and that's only a couple of sets)!! That smelly exhaust is the reason for your fails!! Bob

[besidetheseaside]

Car has a cat, I replaced it a couple of years ago. I have taken the pipe off the PCV and blew down it and it appears clear. I will still take it and the pipes off and make sure they are clear.

[Laird Scooby]

Originally Posted by besidetheseaside

Car has a cat, I replaced it a couple of years ago. I have taken the pipe off the PCV and blew down it and it appears clear. I will still take it and the pipes off and make sure they are clear.

The pipe (which one, there are three at least?) is only part of the PCV system on the red block engine. If you loosen the oil filler cap with the engine idling, what does the cap do? If it stays there under a slight vacuum then the PCV system probably isn't blocked, if it falls or worse still is blown off, that's where the problem lies.

About 3/4 of the way from the front, about halfway down the block on the left hand side (under the inlet manifold) is the oil separator. This could be blocked. Coming up from that is a rubber hose, it might be short (about 2") or longer leading into the bottom of what i'm going to call the flame trap*. This often has a filter inside and that can easily get blocked, however it doesn't appear to have one on turbo models. As yours is a B200F, chances are it will have the filter gauze inside it so pull it apart and check, if it's dirty, clean it with carb cleaner and a twist drill. Anything less than spotless is a compromise.

That said it has two smaller bore outlets (if you consider the stub that goes to the separator as the inlet), one of which is only about 4mm O/D and very small inside and this can easily block.

This has a vacuum hose on it going to the inlet manifold, again the stub on the inlet manifold is small and easily blocked - once cleaned with carb cleaner, use a piece of wire to poke through and ensure the hole is in fact clear.

The other outlet stub should go the the air cleaner side of the throttle body, again ensure it is clear through the hose and also the stubs. The stub could be anywhere between the throttle body and the air cleaner, depending on the exact engine.

Once everything is clean and clear, the only thing left will be the oil separator. As you're hopefully draining the oil at this point like i suggested earlier, you'll be perfectly safe giving it a healthy squirt or even several healthy squirts of carb cleaner through the hose into the oil separator and letting it drip into the old oil as it drains out. Any residaul carb cleaner will soon evaporate off.

If this is the first time you've cleaned the PCV system, do it again in a month or so and then again a month or so after. Then regular oil and filter changes and an occasional clean (once a year or 2 years if your mileage is low) should suffice. It might even be quicker and easier to just change the flametrap :

https://www.partsforvolvosonline.com...431d776da2f144

They also have oil separators on the parent page that one links to, could be a consideration as well. You need to have a degree in Applied Gynacological Mechanics to change the oil separator or long arms, thin fingers and double-jointed joints in every joint from your shoulders to your fingertips.

Joking aside, it's fiddly but can be done if you're patient. I'm not, hence spraying carb cleaner down the hose into the oil separator!

* I mentioned i was calling it a flame trap, there is a school of thought the flame trap is the filter/gauze inside the assembly, i've always known the complete assembly (with or without internal filter) as the flame trap. I've also known engines where the flame trap is that big it wouldn't fit in the engine bay of a 7xx and is called a spark arrestor. Some have been big empty cases, others have had a flap valve inside, some have a bell mouth opposite a plate but they've all been called flame traps or spark arrestors, sometimes both by the manufacturer.

Doesn't really matter what it's called as long as you know where it is and can make sure it's clean inside and in the stubs!

[besidetheseaside]

Right, up early and out and stripped the PCV (oil seperator, whatever you want to call it ) pipes, very little muck in them, cleaned them up including the plastic three way pipe thingy and refitted. Removed the vacuum outlet off the manifold and that is clear, replaced vacuum pipe as it was grotty. Refitted the pipes, took off the filler cap, blew down the pipe from the turbo end ( blocking off the vacuum pipe ) and it blows through clear with no back pressure.
So that is another could be off the list.
The cat I bought and fitted a few years ago was a comparitively cheap one so I am wondering if that has thrown its hand in
Might just fit leads and a new cat and go for a re-test.......
Trying to not let this car get me down, taking the dogs out for a walk to de-stress........

[griston64]

Did you remove the oil separator box that fits to the block ? That can be blocked as well

Its a little fiddly to get at and you will need a new o ring when you refit but they can be pretty gunked up

Sorry to potentially add more jobs to your list but if you are doing pcv there is no point in having clear pipes if the box they go into is blocked

Cheers Mark

[besidetheseaside]

I blew through it with the pipe and is blew through easily so I can only assume ( dangerous I know ) that it is clear. I didn’t want to risk taking it off without having a new o ring in stock. I need to keep it mobile as I am still using it.

[Laird Scooby]

Don't forget to check the small bore stubs on the Y piece and manifold though, i think that may be where your problem is.

Also worth investigating from a slightly different (but still relevant) angle is the earth strap between the head and bulkhead, usually connected at the rear end to either the distributor or rocker cover, it can break or the connections (inside the crimp terminals) can corrode as can the conections on the head and bulkhead.

Might not sound much but the output of the Lambda sensor is 0-1.0V, even a 0.1V drop over a poor connection could send your CO up. Likewise check the battery earth, the battery to body earth and battery to starter earth. While you're at it, also check the alternator earth strap (not relevant to this problem but worth checking while you're at it) and also the earth for the ECU which is hidden behind the drivers kick panel trim.

If you find any bad earths, remove fuse #1 for a few minutes after repairing them.

Just to give you an idea, the Lambda sensor output is near 0.0V when the mixture is lean, nearer 1.0V when rich. Losing say 0.2V will make the mixture much richer, stoichiometric gives an output of just under 0.5V (think it's 0.45V but can't remember without checking) so you can see how it would make a difference!