Hey guys iv this thread on mr2oc at the mo so im lookin for all the help i can get

Im going to tackle this problem in an hour---->

My car failed the test on emissions on....
Low idle (@800rpm) CO reading: 4.5% vol, the limit being 0.5%

High idle was fine.

The car idles rough on start, and when i accelerate it judders before moving off.
When warmed, it doesnt judder. But it idles anywhere between 1000-1800rpm. After long spells of running, it will eventually drop to below 1000rpm, but usually doesnt stay for long.

Its consuming a fair bit of petrol aswell.

Im assuming the failed emissions and the erractic idle are related.

Any suggestions?? Lambda sensor, air flow sensor, throttle sensor etc??? :no:

Car is a Rev3 N/A

Have you checked for codes ? Also try cleaning the TB , this can make a big differance , make sure to clamp the coolent hoses before removing then if you are removing the TB for cleaning

Havnt checked any codes.

Gonna try process of elimination, strating with cleaning of air flow sensor, cleaning of throttle body and replace the lambda, as i got one on recommendation of mechanic.

So heres hoping all goes well

Another thing to ensure is that your spark plugs, rotor, cap, leads are all in good shape. Does you car have an air flow meter?

The AFM is located?? is it at the front of the air filter box?

I'm not sure if your engine would have one or not. They were removed on later model 3sgte's. If you do have one it resemble this:

_KUNENA_BBCODE_HIDEIMG

They can be a source of poor running if they're not connected properly, or if they pack it in.

I checked the NCT manual and the value that you have is very high. Did you remove your CAT?

Nope CAT is still there, i asked the lad at the NCT centre was the cat to blame for the failure, he said no as the high idle passed fine and would probably fail if the cat needed to be replaced.

Dont think iv got a AFM, that meter unit looks very unfamiliar, all i have is a little plug in sensor that goes directly into the air intake box, think its known as the MAF sensor (mass air flow). I popped this out and cleaned it up.

Try having a look through this thread for other suggestions.

Would be great if you could update your own thread on what causes/fixes this prob for future readers.

Update: New lambda sensor installed, car does now drop to normal idle revs of under 1000rpm when running temperature is reached. But its a bit smoky.

Maybe now it needs injector cleaner/Dipthane and a good red line to clean out the fuel system.

NCT retest on thursday. il be updating

Nice one. Give it a redline for me too

The saga continues

Failed again... same problem, high CO emissions on low idle, 3.6% this time (first time around it was 4.6% so little or no change)

This is after changing lambda sensor, cleaning throttle body, changing plugs, dosing with Dipthane to clean injectors and giving it a good redlining

Car is running very rich on low idle, maybe might now change the air flow sensor, this is becoming a process of elimination.

Any more ideas peeps?

Something just crossed my mind...... my cars thermostat is faulty, has been since it was bought 3 months ago, its not the temperature gauge on the dash its definitly the thermostat, gauge never reads half way when driven, the most it reads is about a third of the way.

Is it true that a car will run rich if the thermostat is faulty, as the engine will not reach operating temperature?

*bing - the ECU reads the temperature sensor and adjusts the fueling to suit the engine temperature (i.e. when it is cold, it gives more fuel as the fuel that is there won't atomise properly). The thermostat is there to heat the car up, if you run it for like half an hour and it's still not hot, it's not the thermostat but the temperature sensor that is wrong as that is plenty of time to heat the car up. When you fix that, you will fix your running rich condition and you'll also get much better fuel economy.

Update on this........ car had a SECOND retest today, got one booked before my 28days were up

It passed

Thermostat was changed this morning, coolant bled, and car was given a good redline back to the test centre.

Passed with 0.00% CO and 0 HC's on low idle........ what a result

So moral of the story..... if your car has a faulty thermostat, more than likely it will fail the NCT

Wow good stuff, and thanks for updating and letting everyone know what fixed it for you in the end!

good to hear it

Thats good to hear the car passed .