failed MOT emissions test

[Fiona&Simon]

Ideas please! Our 1998 petrol 2000cc Ford Freda has failed its MOT twice this week because the emissions are too high. Our mechanic who imports Bongos can find nothing wrong with it. Putting in fuel additive and getting engine hot do not cause emissions to fall. They are considering replacing the Mass sensor to see if this makes a difference but otherwise have no ideas. We love this van and had a summer worth of camping activities planned. Can anyone help please???

[BongoBongo123]

A good fuel additive needs some time to remove deposits it won't happen after just warming the engine up and just adding it by itself. Though of course it can be caused by a bad sensor. Typically you need to have something like BG44K in there for a tanks worth and do 300 miles or so to do some carbon cleaning from injectors, valves/combustion chambers etc.

I would also suggest oil change, oil filter change, spark plug change, air filter change the basic service items can make a big difference if they have not been done yearly (the air filter is a big one that can cause a petrol engine to run rich). I imagine the garage may have suggested this ? Get the tyres nice and hard so rolling resistance is a bit lower on the rolling road.(if they use one for the emission test ?)

Sometiems people suggest an Italian tune up... i.e. run it in low gear with revs fairly high to generate a bit more heat than normal to try and burn some carbon off the pistons and combustion chamber. But I would proceed with care with that method you do not want to stress an engine that is not running well in itself. If you have some time before test is due run the car with BG44K in and quality petrol. Give it a bit of a chance chance to do its job.

Good luck with it.

[BongoBongo123]

Just found this elsewhere (not a Bongo another car) worth a look at the exhaust system: "The brilliant chap there took one look at the print out and said "you've got a hole in your exhaust", took the car in, jacked it up and found that the bracket was knackered. (Apparantly this was letting air in to the exhaust system?) "

Does your report look anything like this?

The readouts were as follows:
Fast Idle:
CO Max 0.300% - 7.640% FAIL
HC Max 200ppm - 418ppm FAIL
lambda 0.97-1.03 - 0.77 FAIL

Fast Idle:
CO Max 0.300% - 8.064% FAIL
HC Max 200ppm - 479ppm FAIL
lambda 0.97-1.03 - 0.745 FAIL

Natural Idle:
CO Max 0.500% - 7.543% FAIL

[Bongolia]

Diagnosing emission problems can be tricky especially long distance and if not approached correctly can be expensive with many red herrings along the way.
This problem is exacerbated by the dearth of engine management system information on the Bongo.
However starting at the beginning post your emissions readings; these should have been given to you with the refusal cert.
A few questions too.
Are you experiencing any driveabilty issues.
Did the garage code read your vehicle.
Has the vehicle been serviced recently.
Have you ever misfuelled the vehicle i.e Diesel instead of petrol.
Do you have a digital multimeter and are you familier with how to use it.

[Bongolia]

P.S. too that. Where are you located?

[mikexgough]

Do you use your Bongo often? Short Journeys?..... sometimes if you use a petrol vehicle for short journeys or it is standing for periods of time...the Lambda get "lazy" as if they are asleep..... my MOT shop see that all the time...I took the Mrs car up for test last year and we had to run it for 45 mins to get the Lambda to start working, so not just hot but very hot and with many cooling fan cycles...

[windywatson]

I might be being a bit symplistic, but wouldn't a new cat be the answwer. My van is getting very near to failing really boarder line. Garage said that if failed nex MOT on emmissions it would need a new cat. Isn't this just the same situation?

[Bongolia]

No. Not really. The cat can be overwhelmed by over fueling. If that carries on for a long period it could lead to cat damage. It is essential that emmisions are within "Non cat " vehicle readings before the cat is replace.
On the Bongo this can be checked by an emmisions read before the cat or with the cat disconnected.
On an age basis O2 sensor should be changed also.

[BongoBongo123]

I wonder if Simon&Fiona sorted it ?