Failed emissions NCT BMW

Dr.Winston O'Boogie

Hi all,

My car failed the NCT due to the attached. One of the readings seems quite high but I've had various advise from mechanics. One of the bits of advice was to add emissions cleaners to the engine and then try it again. Do you reckon this would work?

mullingar

Its running slightly rich on low & high idle, hence the unburnt HC.

The first thing I'd do is give it a service to include a new air filter and new spark plugs.

Dr.Winston O'Boogie

mullingar wrote: »

Its running slightly rich on low & high idle, hence the unburnt HC.

The first thing I'd do is give it a service to include a new air filter and new spark plugs.

I had it in for service last week already, I took it back today but they don't have an emissions tester. They recommended a few additives which I have bought to try bring the emissions in line. Would that be enough though?

Skatedude

Then bring it to a garage that can actually fix your car, The mechanic you are using isnt capable of doing so due to lack of proper equipment.

Dr.Winston O'Boogie

Well I found one that does it, got him on phone and he said to add the additives and drive it for a while to bring it down. Then bring it in for the emissions test. Just not sure if that would work?

emo72

Yeah, a bit of dipetane or some such cleaner, is a cheap solution. Try it. Then you have the next year to try fix the problem if you have some money to throw at it.

jca

That's 6 times the maximum limit it would be a miracle if an additive brought it back into line. Are you certain a proper service was done on the car, not just an oil and filter jobbie and a rub of a damp cloth. As was posted earlier you need to see the condition of the plugs, air filter etc. Start at the basics and work from there. Don't be talked into replacing the cat until you find what ruined the first one.

mullingar

+1. No snake oil will fix that difference.

Was the last service just oil&oil filter? If it was, just do what I said in post #2, go get the air filter and plugs changed.

Dr.Winston O'Boogie

Cheers I took it back to the lad who serviced it and showed him what it failed on but he didn't mention the above as a possible option. Not sure what to do now!

Doltanian

Time to change the mechanic or garage you are going to. Try find an independent BMW Specialist. Baverian AutoTechnik in Abbeyfeale are good if you are down that side of Munster.

rex-x

A service, spark plugs or filters or indeed dipetane CANNOT fix a lambda reading that is wrong. You have an issue where you are over fuelling. This may be your front lambda sensor or another issue like injector, MAF sensor etc.

Skatedude

Dr.Winston O'Boogie wrote: »

Cheers I took it back to the lad who serviced it and showed him what it failed on but he didn't mention the above as a possible option. Not sure what to do now!

Er, why? you already said he hasn't the equipment to test it so he can't do it?

Dr.Winston O'Boogie

I didn't know that until I took it back to him and he told me.

Leonard Hofstadter

Are there any warning lights? When the exhaust emissions are out of spec there is an exhaust emissions light in every BMW which should come on to let you know. If the light is on there will be fault codes so any half-decent mechanic will know where the problem is once they do diagnostics.

It's unusual for a BMW to run rich (usually they run too lean if the air/fuel mix is wrong) but the most likely causes are the MAF or duff O2 sensors.

It must be a fairly old car (judging by the limits for the emissions) so there really are only a handful of things that could possibly be causing your problems - and as has previously been mentioned, Diptane or any sort of fuel additives will NOT fix your problem.

Dr.Winston O'Boogie

Yep its a 99 but has been kept in very good nick and hasn't caused my many problems.

A few mechanics have told me at this stage its probably gonna be a costly fix, and its only worth a few hundred euro second hand at this stage so not sure if I should cut my losses.

Leonard Hofstadter

You need to take it to a mechanic who knows what he's doing. There are only handful of possible reasons for a BMW to be over-fuelling - it's either an O2 sensor or a MAF, neither is particularly cheap (and don't use cheap parts as they will only fix the problem for a few months and then you'll be back to square one) but a newer car (which could potentially have problems of its own) isn't going to be cheap either. If it's been reliable until this point, I'd hold onto it and fix it.

What model and engine is it?