Emissions sky high (HELP!)

[PIRTEKMAN]

Hi all,just took the Monty for mot.It failed on one bottom ball joint,a bit of welding required to sills but the emissions are way high.

CO = 11.14%
HC = 2499

Last 3 mots readings have been around co 0.98% and HC 217.

Any ideas what i need to be looking for.All vac pipes seem in order ,air filter is good.Need to sort it asap.Thanks lads.Alan.
ps.I have just had the car idling checking the co and its started to fluctuate from 800rpm down to nearly 0 rpm.it does this a few times and then cuts out.Its never done this before.

[H48HPE]

is the choke returning properly?

[PIRTEKMAN]

is the choke returning properly?

It's a 2.0 efi there is no choke.

[Jeff Turbo]

It's a 2.0 efi there is no choke.

Yes there is.
Not what you would call a choke but inside the throttle housing are cogs inside that control an autochoke and they can become clogged up and stuck. The air valve stepper motor controls them.

[H48HPE]

does the mechanism for cold starting receive its signal from the temperature sender through the ECU? - could it be these at fault?

[PIRTEKMAN]

Yes there is.
Not what you would call a choke but inside the throttle housing are cogs inside that control an autochoke and they can become clogged up and stuck.

Are you on about the stepper motor Jeff.I.ve removed the wiring plugs from the stepper motor and potentiometer,put them back on ,cleaned spark plugs and retested emissions.It's reading about 1% co on my gunson gas tester which earlier on was going off the scale.Will try again tomorrow to see what reading i get.Thanks for your help guys it is much appreciated.Cheers Alan.I also pushed a siff wire up through the bypass hole in the throttle body form underneath(still on car)This may have been blocked but hard to tell.

[Jeff Turbo]

Are you on about the stepper motor Jeff.I.ve removed the wiring plugs from the stepper motor and potentiometer,put them back on ,cleaned spark plugs and retested emissions.It's reading about 1% co on my gunson gas tester which earlier on was going off the scale.Will try again tomorrow to see what reading i get.Thanks for your help guys it is much appreciated.Cheers Alan.I also pushed a siff wire up through the bypass hole in the throttle body form underneath(still on car)This may have been blocked but hard to tell.

Forgive me if i'm wrong as it has been over 20 years since I stripped one down.

If you remove the throttle body, the pipes underneath are coolant pipes and can get mighty clogged up. If coolant doesn't pass through that can affect the 'auto choke'.
Inside the rear of the body (as it's on the car)are 2 or 3 plastic cogs that move the 'auto choke'. These again do get clogged up and stiff.

[E_T_V]

With the HC's that high it is a misfire somewhere. Check/change leads, rotor arm cap and plugs.

[PIRTEKMAN]

With the HC's that high it is a misfire somewhere. Check/change leads, rotor arm cap and plugs.

Will check it all out tomorrow.Thanks Alan.

[PIRTEKMAN]

Yes there is.
Not what you would call a choke but inside the throttle housing are cogs inside that control an autochoke and they can become clogged up and stuck. The air valve stepper motor controls them.

Doesn't the stepper motor just control the idle speed and not the mixture.

[PIRTEKMAN]

Hi all.CO has gone back upto about 5 - 6 %.engine idling nicely if i take the cap off the oil filler tube it drops down by about 1% am stuck for ideas on what to check as it seemed to have cured itself last week .Could the ecu be at fault.

[Jeff Turbo]

Doesn't the stepper motor just control the idle speed and not the mixture.

There are cogs in the throttle body that can get stuck to make the car overfuel. Around 20 odd years ago that was a problem with my MG Montego at the time but I thought u'd cured your problem as your emissions had gone down.

[PIRTEKMAN]

There are cogs in the throttle body that can get stuck to make the car overfuel. Around 20 odd years ago that was a problem with my MG Montego at the time but I thought u'd cured your problem as your emissions had gone down.

problem has arisen again, are the cogs you refer to are the cogs that move the plunger up and down to regulate the idle speed.i cant understand how these cogs can control the mixture as I thought the ecu controled the fuelling.I'm not saying you're wrong Jeff but what other cogs are in the throttle body other than those in the stepper motor.

[PIRTEKMAN]

Looked inside exhaust back box and its gurgling and dirty black watery stuff spitting out of it,any ideas.Car idling lovely ,no overheating,water level fine,no water in oil.i'm baffled.

[E_T_V]

The EFI stepper motor just increases the air supply to the engine. The mixture is adjusted electronically.

On the carburettor cars the stepper motor adjusts both the mixture and the idle speed together.

If the stepper motor is clean, what speed does the idle sit at? It should be ~1000rpm when cold decreasing to 750-850rpm when hot I believe. If when the gauge is in the middle indicating normal temp the idle speed is still high then this is likely to be due to a duff ECU temperature sensor or the wiring to it (I think there is a seperate ECU temp sensor and gauge sensor).