Ford failed MOT on High CO emission

If it idles high, with it in park, block off mouth of throttle body with something, it should kill the engine. If very little or no effect on idle, you have false air getting in there from somewhere.
Make sure throttle valve is closing, where applicable, take throttle cable loose, see if idle returns to normal. Check and clean idle air system. Any applicable trouble codes?

Replace your oxygen sensors.
murf427

Replace cat. The mechanic was correct.

the O2 sensor works on one volt .5 is around the running voltage, i would refit the air hose as it will run the converter hotter at idle.

give it a good hard run and make sure its hot when taking it for its retest. easy as that

check both lambda sensors for breaks in wires and for open circuit on heater side of lambda sensor on the one under the car on the second cat,failed heater element will not heat gas engough for sensor to read causing false readings , also check for slow i.a.c valve on inlet manifold.

yes it's a lot of work but another engine from an escort the same as yours should fit onto mounts, gearbox ect

Hi Don,

First, thank you for asking me for my input on this. It just so happens, that I used to own a Ford ranger that had the same engine as yours. It was a 1990, but there are few changes to these model years.

Anyway, there is only one reason that your HC levels would be high. Your engine has WAY too much unburned fuel in the exhaust. The same reason applies to high CO levels. Too much fuel and/or not enough air.

Below is a link that you may find very helpful. It explains exactly what we are talking about here and also lists some of the possible causes.

EMISSIONS ANALYSIS

Incidently, when I had the same emissions failure on my truck, replacing the air filter and replacing a failed MAP sensor fixed it. - I did NOT have to replace the catalytic converter. If the numbers are as high as you listed above, you will only destroy a new converter anyway because there is obviously not enough oxygen in your exhaust system for the catalyst to function properly. Those numbers are nearly DOUBLE the allowable maximum. If the engine is running correctly and the catalyst is good, your numbers will be WAY BELOW those maximum numbers.

Please understand that I am NOT telling you to replace your MAP sensor without proper diagnosis. There are many possible causes here. Please click the link above and read the article. It will help you to understand what is going on here.

maybe timing, it has a chain.... 

The advice that the garage gave you seems right. If any bushes were worn they would show up on the MOT Test. Try taking it to another garage to check out the Cat for your peace of mind.