Failed Emissions test

Post Fri Mar 27, 2015 3:52 pm

Hi,

Have had my 1987 325i (pre cat) down for its MOT today. I sent it in with a new set of tyres to be fitted and besides that was expecting all to be well.

I have called up to check on progress and it has failed on emissions. I have noticed no change since the last MOT in which nothing was mentioned.

Has anybody an idea on the probable course? Would it be acceptable to take it for a spin to warm up and expect to see any change in the readings?

Any advice would be appreciated. Many thanks

Post Fri Mar 27, 2015 3:57 pm

Post up the emissions readings from the failure sheet. Someone will be able to advise you better.

Post Fri Mar 27, 2015 4:03 pm

That's what i'd like to do, but haven't had chance to pick the car up yet. I will do so once collected. Thanks

Post Fri Mar 27, 2015 6:25 pm

Rtaylor2208 wrote:Post up the emissions readings from the failure sheet.

O2, CO and CO2, if you can get them.

Post Sat Mar 28, 2015 1:12 am

Have my car back now having passed the 'Emissions test' on the second visit.

In the end I feel they've just weaned an extra bit of cash out of me for no real cause. I hadn't looked at the Emissions results until finally passing but now see that it was broken down into the following;

CO:- Limit: <3.5% Actual: 2.012% (pass)
HC:- Limit: <=1200 PPM Actual: 162 PPM (pass)

and then the fateful;

Smoke Level:- (fail) with the statement "Exhaust emits clearly visible black smoke during acceleration

So before realizing this is why it failed I took a chance and went along with their suggestion to add some of their (over priced) Redex equivalent potion. 10 minutes later its passed!

I've never seen any black smoke from the exhaust, and it is by no means as bad as so many of the dirty diesels I find myself stuck behind in traffic. So at the end of the day I feel a bit cheated, but with no other issues or advisories finally quite pleased.

Thanks for your advice earlier today!

Jack

Post Sat Mar 28, 2015 7:12 am

Pretty sure that HC reading is lower than it should be - CO is probably slightly higher ? I thought about 1.5 was optimum.

One thing I have learned over the years with any car petrol or diesel is to take it for a good blast, get it properly hot and then drive it to the MOT station and get them to put it straight on the machine.
This is even more important if your car is not used regularly. That way you stand a chance of getting any crap out of the engine before it gets tested.

If the HC is low IIRC that indicates it's running lean - check for air leaks and also get the valve clearances re-set.
I had similar HC readings on my last MOT and resetting the clearances seems to have sorted it - plus it runs a lot bette

Post Sat Mar 28, 2015 10:15 am

It may have scraped through now, but this is a German engineering masterpiece you are driving, not some ten year old Ford scrap! The emissions figures on all but the most badly neglected E30s shouldn't be far away from what was specified at the factory, and should be about 1% CO. It should be able to be adjusted to be far lower than this, but 1% is about optimum for a balance between power and economy.
Your car appears to be running slightly rich, which needs investigating - it's costing you dearly in terms of MPG and BHP at the moment.
Blue temperature sensor and its wiring would be the first thing to thoroughly check, followed by a measurement of fuel pressure after the engine is stopped, to check for a weeping injector.
Have the injectors ever been rebuilt?

Post Sun Mar 29, 2015 2:09 pm

I appreciate what you're saying regarding the high CO levels and plan to look into this although being told that the car failed on visible smoke from the exhaust is bonkers!

For a bit of background info, I use the car pretty much daily (covering about 15,000 a year) with a combination of driving to include a fair bit of motorway. My economy will rarely drop below 25, and maintain around 30 on the motorway. I cant imagine this improving greatly, but may be wrong?

Considering both of your suggestions; I have recently replaced the manifold intake boot after finding a small tear. No other air leaks are evident.

I adjusted the valve clearances just short of a year ago and will be doing again soon.

For piece of mind I also checked out the blue temp sensor and wiring when I found a relevant thread on here.

Something I haven't done and have been considering for a while is an injector rebuild. You mention checking the fuel pressure after the engine has stopped. What sort of pressure should I expect to see maintained?

Finally I'm overdue a new air filter, so will change this very soon.

Thanks

Post Sun Mar 29, 2015 3:19 pm

In my experience if a car emits excessive black smoke, it won't go through the emissions machine.

Have you got a pass and fail certificate for the car? You can have a look the the times it failed and passed.

Post Sun Mar 29, 2015 3:24 pm

Jookeone wrote: You mention checking the fuel pressure after the engine has stopped. What sort of pressure should I expect to see maintained?

Should maintain the pressure it stops at for days without dropping appreciably.
Dirty air filter will push up CO (and MPG and BHP down) appreciably.

Post Sun Mar 29, 2015 6:30 pm

I've got the 2 results one for the pass and the other for the fail, with little difference between the values... Just the fact they decided to fail it on smoke level the first time! Will try and dig out the results from the past couple of years for interest

I'll be changing the air filter, and checking the fuel pressure when I get a chance then. Would be nice to get the figure down to factory spec!

Post Sun Mar 29, 2015 6:44 pm

I was talking about th actual MOT certificate.

You said they rang you to say it had failed and it needed a fuel cleaner to pass. Some garages will PRS a car (which will print out a fail and a pass certificate, this is used for small items usually) some garages will PRS a car as its hassle failing fitting a bulb for instance and then retesting so the tester will just fit a bulb at time of test.

Just check the times to make sure they're not pulling one over on you.

Post Sun Mar 29, 2015 6:49 pm

Oh right I'm with you, in this instance they do have two different times to suit. But that's worth noting in the future.

Thanks

Post Sun Mar 29, 2015 6:52 pm

Jookeone wrote:Have my car back now having passed the 'Emissions test' on the second visit.

In the end I feel they've just weaned an extra bit of cash out of me for no real cause. I hadn't looked at the Emissions results until finally passing but now see that it was broken down into the following;

CO:- Limit: <3.5% Actual: 2.012% (pass)
HC:- Limit: <=1200 PPM Actual: 162 PPM (pass)

and then the fateful;

Smoke Level:- (fail) with the statement "Exhaust emits clearly visible black smoke during acceleration

So before realizing this is why it failed I took a chance and went along with their suggestion to add some of their (over priced) Redex equivalent potion. 10 minutes later its passed!

I've never seen any black smoke from the exhaust, and it is by no means as bad as so many of the dirty diesels I find myself stuck behind in traffic. So at the end of the day I feel a bit cheated, but with no other issues or advisories finally quite pleased.

Thanks for your advice earlier today!

Jack

That's possibly a load of bollocks.

The CO is perhaps a tad rich but not excessive - ideally it needs to be around 1% but the PPM's indicate that it's running well. The black smoke under acceleration is them trying it on and the smoke test is purely discretionary.

Still, you have an MOT so.........

Post Sun Mar 29, 2015 7:01 pm

Yeah I'm happy now at the end of the day. The "black smoke" was never a concern as I know it doesn't! Like you say most likely them trying it on...

It's overdue a filter change so I'll do that regardless, might be all that's in it with the CO level!