it failed the MOT on emissions....anyone seen this before?

[jimbom30cab]

1992 318i cab M40 ”“ all standard apart from aftermarket exhaust.

So I took the car for an MOT today, it’s been off the road for a year for bodywork repair, nothing mechanical at all. It failed on the emissions, they said the lamda and CO were a little high but only just. I’ve not run it for a year and done nothing mechanical on it.

The guys put some additive in the tank and said to give it a good spirited drive for a few days and bring it back and it should be ok.

It also has an issue with idling and when lifting off the throttle the revs drop down to about 500 and it almost stalls then picks up to about 1200 has a little oscillation and becomes stable again around 900 ish. I just wondered if the 2 faults were connected?

Should I :

-check for vacuum leaks?
-Clean the intake system with carb cleaner?
-Test the ICV ”“ not really sure how to do this but there must be a guide here or in my Bentley manual?
-Give it a good thrash and fill up with super unleaded?
-Check the AFM flap is working ok and the resistances are in spec? again not too sure on this but know I’ve read some guidance on here somewhere.
-Is it worth doing anything else like new leads and plugs or change the engine oil etc, a good service wouldn’t do any harm but I was reluctant to spend too much as I’m changing the engine this winter anyway.

Thanks for any help

Jim

[toby]

I'd start with the basics as they suggested.

Clean the plugs - check the gaps.

Clean out ICV.

Thrash it.

See what it's like after that.

[Morat]

forget the super unleaded (makes no odds on our engines) take it for a good drive and then see how it idles. Top it up with nice fresh supermarket unleaded - cheaper fuel sells faster

Forget the new leads - not required unless you can see damage.

You'll probably find that with a fully charged battery and an ECU that has relearned the fuel trims you'll have a better car.

Then do the rest of your list anyway because it probably needs it!

[Brianmoooore]

Was your car tested to the post 08/92 emissions limits, or before? (Cat or non cat?.)
One cheap and simple item missing from your list is a new air filter.

[jimbom30cab]

Hi Brian, i'll check with the garage but the car is Feb 92 so i hope before. Air filter added to list thanks

[Brianmoooore]

Hi Brian, i'll check with the garage but the car is Feb 92 so i hope before. Air filter added to list thanks

Ask them for the full gas sheet - you should have been given a separate sheet of paper from the gas test printer.

[jimbom30cab]

ok will pick it up on the way to work tomorrow and report back the details.

[matt86]

surely thats a car with a cat if its a 92, change plugs, clean icv, put some redex in with the fuel to clean injectors.

After that you might want to look into rotor arm, dizzy cap, ht leads.

If it still fails emissions, cat may be knackered. HTH

[jmc330i]

surely thats a car with a cat if its a 92

Not necessarily on a Feb 92 car, as Brian said above, August 92 is the date.