Z3 Failed MOT today - Emissions - Need Advice

[danieltharris]

Hey guys,

My emissions caused the 1.9 to fail today.

According to the guy on the phone it failed by .68 on the first test and .42 on the second, but i'll get the printout when I pick it up later. Do these numbers mean anything to anybody?

Has it only barely failed, or is this a significant amount.

Reason is I spoke to a BMW independent today who usually do all the work on the car and he said if it has an aftermarket cat then it is common for the z3 to need to be taken for a good run before the emissions are tested and also to put in a fuel treatment similar to Red-X during that drive.

I do use optimax or it's equivillent anyway 90% of the time (if it is available when I need fuel) so I always thought that eliminated the need to ever use Red-X etc?

Anybody heard or experienced anything like this before? This car does have an aftermarket cat but it passed with no problems the last 2 years.

I don't want to go replacing all the parts that may be causing it and waste a lot of money, there is NO engine management light on the dashboard or anything, so does this mean there won't be a fault code if I get it scanned?

The things I am thinking it could need (if what suggested by BMW Indy doesn't work):

- New Cat
- New MAF
- New Oxygen Sensor

Replacing them all at once and hoping it passes next time doesn't seem like a good plan!

Any help appreciated

[Guest]

You do not say what the failure was caused by - MoT tests are taken on CO and hydrocarbon emissions, at both idle and 'fast idle' rpm.

Look at your failure notice, and see what the engine temperature was when the tests were carried out - it should be about 80 degrees C, as a cold engine will be too rich, with high levels of both emissions. also check the Lambda probe voltage, as this also has a bearing.

Perhaps new spark plugs may help - how old are they? Also - was the car driven hard before the test? A good drive (eg 70 mph in third gear for a few miles) will clean out the engine and help to reduce emissions.

[c_w]

RedX is a thing of the past and doesn't do much to modern injected engines IMO.

As Mike said, how the car was driven before the test can influence the emissions test, a proper , not a quuick drive so it's up to temp according to the gauge, it needs a good drive, on the motorway at high revs to get the cat full up to temp and also the oil too. The only problem is they tend to do the emissions last so even if they let it idle for a while the temperatures will get slightly lower again.

[Guest]

Here in France, we make an appointment for the test, arrive on the dot, and the emissions are the first thing they do. Sensible and logical.

My UK MoT was always done by the same BMW dealer, and every year the CO level had exactly doubled, which looked less than truthful.

By 2004, when we moved to France, I would have had a failure on CO levels, and had to buy two new cats - or a new exhaust system.

My first French test - and all subsequent ones - gave a level of 0% for CO.

[Adam]

I recently had the same problem, failing big time on emissions. After disputing it with the garage I was proved right. The car really has to be warmed up and cat upto full operating temp. Most garages leave the car running for 10 min then test it..giving a false reading in reality. After I took my car out and ran it for 30min, through the gears and holding a good rpm and getting it really up to temp...took it back and hey presto...passed with flying colours.

I wonder how many people get had by substandard mot testers not warming cars correctly.

[estocks]

a 50% difference between the two readings means they are useless in my opinion.

[Robert T]

I watched my one of my MOTs being done. The guy left the car running whilst he checked everything else and did the emissions test last. As usual is passed with very low emissions. There is very little to be gained by them failing a car simply on emissions because it isn't up to temperature. Best advice is find a good garage and stick to it - the good ones appreciate customer loyalty.

Cheers R.

[Foggy]

Seems to be catching, my Z3 (R reg 1.9) has just failed an MOT today on emissions as well; at local reputable garage owned by ex-BMW service guy.

Fast idle CO 0.504% and Second Fast Idle CO 0.547% (8.5% up). Lamda was 1.025 and 1.023 respectively.

I warmed the car up before handing it over (but not a full motorway warming as detailed above) but they did not test emissions until over 2.5 hours later, and though the say they ran the engine to warm up before the test, it looks like it was insufficient.

No engine oil temperature on the test results, just a note saying engine oil temperature measurement was by-passed!

Off to see the garage owner tomorrow to get it sorted (unfortunately he wasn't in today and he is main MOT tester). New CAT and/or Lamda sensor mentioned when the passed over the MOT fail certificate by other tester.

Assuming it is just a temperature thing, any suitable words or phrases (repeatable that is) I can use tomorrow would be useful.

Presumably get them to agree a fixed re-test time, get the car warmed-up properly, turn-up on time and make sure they test it there and then.

By the way if you have no existing MOT would it not be tricky if you were stopped on a motorway travelling in the opposite direction to the MOT garage!

[GE45TON]

My 1.9 has just failed as well, no fault light but had an error code for the O2 sensor also had a rubbish exhaust fitted by the previous owner, new parts being fitted now so hope it passes the test. Did try some Wynns and a blast down the A14 but didn't make much difference, what fixed your failures?

[Deano1712]

Fast idle CO 0.504% and Second Fast Idle CO 0.547% (8.5% up). Lamda was 1.025 and 1.023 respectively.

You are not far off passing there. The lamdba is good. If the CO was a genuine problem you would be running rich (<0.97). The cats will come up to temperature at fast idle if held there for a few minutes. I watched this on my car last week and the fast idle CO came down from 1% to 0.05% suddenly when the cats got going. You need to get it retested.
Sadly mine is at 0.95 lambda at idle so failed - looks like I have a small leak on the manifold to fix.

[Del]

Several people I know in the motor trade have recommended running a bottle of Cataclean through the system before an MOT.

[GE45TON]

I suppose many Zeds are used for short trips and weekend blasts, this probably doesn't help the engine and exhaust to run at decent temperatures and may cause emissions to creep up over time. Mine has passed the MOT now after a new O2 sensor and Cat, only thing is now since picking it up from the garage I have a clicking noise coming from either the diff or a driveshaft, not sure what's going on with that but wasn't there this morning! Not impressed with the 3 tyre valves wedged into the exhaust mount to align the rear box either!!!

[houdini2005]

a friend told me to use this a couple of days before my mot http://www.amazon.co.uk/Cataclean-Catal ... 631&sr=8-1 seemed to work , mine passed on emissions but failed on a sh*t load of other stuff rear springs

[Mike Fishwick]

Give the thing a decent run - a few miles just before the next MoT at 70 mph in third gear will do it no end if good.