Low idle emissions failure

[seaniep]

Hi lads need a bit of help with a problem that I incurred today during my NCT.. Looks like my emissions at idle are a bit on the high side.. Like the limit is 3.50% and shes coming in at 8.30%, thats nearly twice the limit.. Oh ya the cars a mk1 1.6.
Just had her serviced and the whole lot. Any one have any ideas what it could be???

[Steve]

Best check air filter, air leak in the intake, plugs, plug leads, change oil, check O2 sensor, swop out MAF with a known good one...

[franksm]

hey dude

Are you handy with a multimeter ? If so, read on. If not, ignore the following as it'll be as useful as you reading an eyetest in Polish

You can check the O2 sensor, AirFlowMeter (AFM) and temperature sender in situ right where they are on the engine, and/or you can test for them at the ECU. Either way, here are the pins and numbers to check for (letters in square brackets are the wire colours):

- AFM (ECU pin 2O) - should show 3.8V on your voltmeter at start or idle; [R] wire at ECU; [LG/R] at AFM
- Temp sensor at back of cylinder head - should be 2.5V cold, 0.4v after warmup [B/LG] ECU pin 2Q
- O2 sensor – ign on, engine stopped should show 0v; idle on cold engine also 0V; idle on warm, 0 to 1V); increase rpm engine warm, 0.5 to 1.0V); deceleration 0 to 0.4V); ECU pin 2N
- Intake air sensor (within the AFM) – at 20 deg C should read approx. 2.5V. [R/G] wire going to ECU 2P
- Injectors should be 12 to 16 ohms each
- Idle Speed Control Valve (ISCV) - should be 7V when ignition on with engine stopped, 9 volts during idle. ECU pin 2W
- ISCV – engine warm, disconnect the wiring plug and check for clicking at idle; idle should also increase to 1200rpm
- ISCV – check resistance – 11..13 ohm at 20 degrees C
- Throttle dashpot rod = check resistance, press rod with your finger and make sure it returns
- Throttle dashpot setup = engine at 4000rpm, slowly reduce to 2500rpm and check throttle lever just touched dashpot rod at this speed
- PCV valve – clamp hose and check RPMs do not fall. If it falls, check PCV valve

[seaniep]

Wow Frank there's some amount of info in that post.. Can't wait to show my mecanhic this post...lol..

So today i took off the air filter (sports cone filter) and cleaned it up sprayed the oil on it and also took off the AFM cleaned it up seems to have made a difference to the running, While i was at it i noticed that a small pipe on the throttle body was blocked so i took off the blank and put a small cone filter on it, its pulling a vacum into the throttle body since i put it on the car seems to be running smother..
Anyone know what this pipe is for???

[2me]

Id the same problem with mine (eventhough it was not reading as high), Im retesting on Wednesday. First thing you should do before spending any money is read any fault codes. This should help http://www.mx5oc.co.uk/forum/forums/t/204.aspx. Are you having any idling problems mine was fluctuating when it warmed up? When I read the fault codes the O2 sensor came up as faulty Ive since changed this for a new one from MX5Parts. It seems to be idling steady at about 900rmp & the fault codes have been cleared. Fingers crossed for the retest on Wednesday.

[seaniep]

Thanks for the info 2me..

[turismo2142]

How'd you get on with that retest 2me?

[2me]

It passed. I changed my O2 sensor looks like someone was at it before as the old one was loose and damage. I also gave the idle control valve a shot of carb cleaner and between the two I was able to get rid of the fluctuating idle and get her idling at 800rpm. I've done about 300 miles since yesterday and fuel economy is much improved and idle is perfect

[2me]

Just spotted your cork I'm in cork a few times a week if you want me to help some evening

[seaniep]

Would you believe my emissions are practically non existent at present. Took of the air flow meter and put in a injector cleaner and now have readings of 0.04% CO2. Test booked for next week so looking forward to passing:)

Cheers 2me for the offer.