Maestro 1.3 Emissions.

[Richard H]

Just taken my low mileage 1.3 Maestro for its first MOT since 1999, the tester commented on how clean it was but unfortunately it failed on one thing, emissions. It's already had an oil and filter change, new air filter, plugs, new dashpot oil and a good blast, but it still failed, with both the CO and HC off the scale :( The garage tried to adjust the mixture, but they couldn't get it down enough.

Any ideas?

[ChrisM]

Vacuum pipes! They'll be well perished I bet.

[Richard H]

When I bought it there were a couple of odd things, firstly the air filter was missing, and secondly most of the vacuum pipes were missing or broken. I found a thread on here about where each pipe goes so they are all connected up in the right place with lots of replacement pipe :confused:

[E_T_V]

Is it firing on all cylinders? If not the emissions will always be off the scale

Is it an auto-choke model or a manual choke one? As you can't just tweek the mixture on an auto choke one it gets confused.

[Richard H]

It's firing on all cylinders, it runs very well apart from a bit of roughness for the first three or four seconds after starting from cold, which also requires a fair amount of throttle to start. It is still on the Auto choke, could it be a problem with this? Sorry I'm new to all this :rolleyes:

[E_T_V]

You need to set up the carburettor from scratch as it sounds like someone may have meddled with it.

Check that the autochoke is actually working properly. If it is still overfuelling then check the autochoke O rings as if they have split then it'll overfuel like mad.

[G Force]

If you can't get the CO level down, the vacuum switch diaphragm is probably split.

To check the vacuum switch first you need to move the air filter box out of your way.
1. Disconnect one end of cold air hose from air filter box or bonnet slam panel.

2. Remove one end of the large hot air hose that fits on the filter box & on the exhaust manifold hot air shroud.

3. Remove the 3 large screws from the air filter box, no need to remove the small posi screw that secures the lid.

4. Swing the air filter box out of your way; it will still be attached to the engine by a small vacuum pipe underneath. Note the rubber gasket on the air filter box around the air outlet to carb.


Once you can see the carb look for the vacuum switch (1st picture) it can be seen attached to carb on (2nd picture). Pull off the small vacuum hose then remove vacuum switch from the carb by prising it from the two rubber hoses with a suitable screwdriver. Test diaphragm for any air leaks by sucking on the small single vacuum port. (If you suck on the vacuum connection you should not be able to suck air through). If you can suck through the switch you need a new one LZX 2292 will be OK.

If this is the prob the CO will need to be reset once the new switch is fitted.


http://www.maestro.org.uk/forums/attachment.php?attachmentid=3516&d=1186084329

http://www.maestro.org.uk/forums/attachment.php?attachmentid=3517&d=1186084445

[Austin-Rover]

If you are still running on the auto choke, and would like to keep this original feature, it can be made to work reliably. You might find people in the motor trade suggest you ditch it for a manual conversion...which is not necessary.

fit a pair of upgraded Viton O Rings to the stepper motor, and retune the engine to suit and away you go!

[Richard H]

Thanks for all the responses :)

Right, my dad stripped down the carb today, the "O" rings look ok, the vacuum switch is fine, but the jet? in the bottom of the float chamber appeared to be stuck. This has now been freed off. I bought a Gunson's Gastester and we have checked the CO, it's now around the 3/3.5 mark which I think is a pass.

Unfortunately it is still rough for the first few seconds of running from cold.
My dad told me there was something else that had seized up as well, but I can't remember what it was... :confused:

[Austin-Rover]

Your O rings may look okay, but most likely they are knackered. Unleaded petrol causes them to swell and allow too much fuel past, which messes up the running of the car when on choke. A new set should have the choke working nicely.