Help please - MOT failure

[Cardiff Steve]

My 1.9L baby has failed its MOT with the not-unusual CO problem. We think we have done the obvious. We did a smoke test and have replaced a cracked pipe. We have replaced the airflow meter as the readings from it didn’t change when connected to the computer. We have run it hot and retested and still it is failing.

The issue is that at 2,500rpm the engine isn’t holding a steady speed - it is varying +/- 200rpm and the CO readings are also going up and down. When it is steady, CO readings are OK.

Does anyone have any suggestions?

I’m happy to spend the money if I know I can fix the problem. I’m in danger of part-swapping and hoping for the best at the moment.

 

[Nodzed]

@colb can you help with your wizardy kit?

 

[colb]

Can do back home late tomorrow from our Cruise so Shed back to normal next week. Steve pm me and we can arrange to plug you in to see what's going on, is it drivable or will I have to come to you? I'm in Newport

 

[Cardiff Steve]

Can do back home late tomorrow from our Cruise so Shed back to normal next week. Steve pm me and we can arrange to plug you in to see what's going on, is it drivable or will I have to come to you? I'm in Newport

Thank you for your offer. The car is running but the MOT has expired. It’s still with the garage at the moment, they are going to try again Monday morning on their computer analyser. I will post an update and contact you if they draw a further blank.

 

[Nodzed]

Thank you for your offer. The car is running but the MOT has expired. It’s still with the garage at the moment, they are going to try again Monday morning on their computer analyser. I will post an update and contact you if they draw a further blank.

I would suggest that Colb would be of more use to you but it's your call.

 

[colb]

Made a visit to the Garage in Cardiff where Steves car is languising following MOT fail on emmissions.
Car has flat battery so garage put a power bank on it to jump start it. Immediately noticed a very rich smelly exhaust.
They had previously put a new intake boot on to replace a split one and put a non oem Maf on the car.
Scanned with my Launch Scanner revealed a code for the Maf and the Intake air temp sensor. Cleared codes and they came back.
Used software on my Laptop to view the Lambda sensors qand pre and post cat sensors performing as they should. Fuel trims checked and these looked ok and quite stable. The Maf when viewed was reporting but the intake air temp sensor was reading extreamly high, disconnected it went off the scale so that is duff. Not convinced the non oem Maf is reporting correctly. With the Maf disconnected the engine ran smoother using the default settings. Cleared adaptions and cleared all codes again, The Maf and intake temp codes returned.
Cleared again and put the car on the garages exhaust tester to see if we had made any difference, alas it failed on the CO readings again.
Suggestion is to replace Maf with oem Bosch or Seimens and an oem air intake sensor and rescan the car to see if it loweres the emmissions. If it dosn't then the Cat may well be the cause. The car has over 100k miles on it so its a possible cause besides the Maf and Intake air temp sensor. Garage going to change the sensors for oem, will see if they resolve the issue. Car is a 1997 M44 engined Z3.

 

[Stevo7682]

If it needs a cat the stuff you get from euro car parts etc no where near as goid as bmw one .
Original bmw part into 4 figure sum.

I have one of these fitted on my m44 got through 2 mot with it now cat fitted is a euro 3 type approved cat so much better quality than the euro 2 stuff that euro car parts give
Stephen

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[Stevo7682]

This thread will let you see the difference between the type approved cat and euro one

Emissions M44

Hi Guys time for a story that will get to a point 🤔 ( I promise) When I bought Lynne's zed got it cheap as it had a number of serious issues but let's not diverse to much . One of the issues was it had a bit of a major starting and running fault after a bit of diagnosis ended up with the...

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