Engine misfire? Failed emissions again!

[Danny172]

Hi all
I’m hoping someone could point me in the right direction as getting seriously close to torching this thing!
I have a 98 z3 1.9 16v and year on year it’s struggled to get through on emissions.
Things done are
New plugs, injectors overhauled, fuel pressure valve replaced, replacement cat ( was said the cat was wrong 200ppm should be 400 ppm), I’ve checked the intake boot from the air filter and carried out a smoke test on the vacuum lines. The only things I haven’t checked, or replaced are the coil pack or the plug leads.
The car drives fine, no hiccups or anything, also the engine at idle is a little shaky, smoothes out with revs.
The car doesn’t smoke at all, but I think the exhaust smells a bit rich…although I am used to diesels.
When revs are held at approx 2000rpm, the exhaust sound a bit “fluffy”.
Just got back from the mot station and at idle the emissions were about 87 ppm, should be 22ppm if I am correct? The test was repeated over and over, keeping the revs at about 2000rpm…eventually the figure came down (brand new cat) to pass.
I want to get this resolved and do have a creator cp110 plus code reader (there are no codes stored).
I’m pleading for anyone to give me some pointers where to go next!
Many thanks
Danny
Ps the maf sensor changed also for a known working item

 

[Ianmc]

Was it an OEM cat?

 

[Danny172]

Hi there
No it wasn’t oem. I could see the cat was working as it brought the emissions down once nice and hot, my issue is more with a misfire I think

 

[John_B]

Just my 2 cents, but when I bought my car (also '98 1.9 16v) last year it had failed on emissions and I had the exact same symptoms as you - shaky idle & rich smelling exhaust. The advice I got from various sources, including here, was that it could be anything and that people have spent thousands on new parts and diagnostics and never gotten to the bottom of it.

In the end, I got mine through after using a bottle of Cataclean, a spirited drive to the test centre and a tester who said, and I quote - "I just revved it until it passed". His advice now the car was MOTed was to keep driving it regularly and to use premium fuel. Since then I have changed the thermostat as it was running cool and addressed a small vac leak (unsure if related to high emissions but surely won't have helped).

Next MOT is in September so we'll see how it gets on. If emissions is still high my next step is going to be a type-approved cat. This link doesn't work anymore, but shows the sort of thing to be looking for:

This is my build thread, you can see a few comments re: emissions on the first couple of pages

'Tandy' - First project car, first Z3!

Hi guys, This is 'Tandy' (named by the wife). He's only a 1.9 and has done 180k - so it was cheap, and is not the end of the world if I totally f*** it up! I picked him up last weekend and drove him home to tuck him away on my driveway before his current MOT expires. The previous owner sold him...

zroadster.org

Good luck!

 

[Stevo7682]

Hi Danny readings for BET emissions test are
Co 0.2 max ( carbonmonoxide ( what cat cleans))

Hc 200 max ( hydrocarbons (unburnt fuel))

Lambda 0.97 - 1.03 ( oxygen sensor readings)

Reading your thread you seem to have covered most of the M44 engines issues.
The M44 is quite a rich burning engine at the best of times unfortunately aftermarket cats are generally not the best quality and tend to only last a year or so.
I and a couple of other members have a cat from Germany which comes with a euro 3 type approved cat which is far better quality than the aftermarket euro 2 standard cats.
Stephen.

 

[Ianmc]

For benchmark purpose, my 2 year old OEM cat on the M44 produced following results last month:
Co 0.00 (max 0.20). Fast Idle test
Co 0.00 (max 0.30) Natural Idle test.
HC 14 (max 200)
Lamdba 1.003 (max 1.03)
Unfortunately, my experience is that only the OEM cat will suffice for the M44 engine. They are not of course cheap, for a reason.

 

[Danny172]

Just my 2 cents, but when I bought my car (also '98 1.9 16v) last year it had failed on emissions and I had the exact same symptoms as you - shaky idle & rich smelling exhaust. The advice I got from various sources, including here, was that it could be anything and that people have spent thousands on new parts and diagnostics and never gotten to the bottom of it.

In the end, I got mine through after using a bottle of Cataclean, a spirited drive to the test centre and a tester who said, and I quote - "I just revved it until it passed". His advice now the car was MOTed was to keep driving it regularly and to use premium fuel. Since then I have changed the thermostat as it was running cool and addressed a small vac leak (unsure if related to high emissions but surely won't have helped).

Next MOT is in September so we'll see how it gets on. If emissions is still high my next step is going to be a type-approved cat. This link doesn't work anymore, but shows the sort of thing to be looking for:
View attachment 304265
This is my build thread, you can see a few comments re: emissions on the first couple of pages

'Tandy' - First project car, first Z3!

Hi guys, This is 'Tandy' (named by the wife). He's only a 1.9 and has done 180k - so it was cheap, and is not the end of the world if I totally f*** it up! I picked him up last weekend and drove him home to tuck him away on my driveway before his current MOT expires. The previous owner sold him...

zroadster.org

Good luck!

Hi thanks for the reply!
I’ve completely run out of ideas, but I’d you do need a cat, I’ve got exactly the same item up for sale in Facebook marketplace still in its packaging!

 

[Danny172]

Hi Danny readings for BET emissions test are
Co 0.2 max ( carbonmonoxide ( what cat cleans))

Hc 200 max ( hydrocarbons (unburnt fuel))

Lambda 0.97 - 1.03 ( oxygen sensor readings)

Reading your thread you seem to have covered most of the M44 engines issues.
The M44 is quite a rich burning engine at the best of times unfortunately aftermarket cats are generally not the best quality and tend to only last a year or so.
I and a couple of other members have a cat from Germany which comes with a euro 3 type approved cat which is far better quality than the aftermarket euro 2 standard cats.
Stephen.

Hi stephan
The cat was literally a day old, and type approved. The readings eventually came down as it got hotter.
I’ve scared myself silly on the internet thinking it could be a burnt out valve, head gasket etc

 

[t-tony]

Post a picture of the emissions Fail cert.

Tony.