paulhumphries
10-04-2006, 02:02 AM
My 1990 Golf MKII 1.8 GL auto has just failed MOT on excess emmisions.
Mileage is approx 128,000 miles
This is the third year running.
First year tickover was too unstable to test so I ended up replacing Piersburg with brand new Weber twin choke carb (manaul choke). It was a proper kit for an auto with the solenoid vac valve to alter timing when gear selected. The MOT tester said the emmisions were perfect "straight from box" and didn't need any adjustment to gain pass.
Soon after the rubber base split so that was changed.
Last year emmisions were too high so I adjusted them with my Gunson Gastester but didn't get them down far enough so tester tweaked it the required 3% needed to get a pass. I assumed the split base might have been the cause for gaining a pass when first fitted due to air leak and didn't worry about it needing adjustment
This year they are back up to over 6% with sky high hydrocarbons.
The car is in good condition with recent new plugs of the proper three pronged type. The plugs are black and dry indicating rich mixture.
I thought it would be something simple like sticking choke or blocked air filter but they are both OK.
BTW the engine breather ISN'T currently connected to the air filter box so that cann't be affetcing emmisions. The Weber conversion means the pipe wasn't long enough and I've never got around to doing anything about is as no fumes .
Anybody ideas what can be wrong ?
I should add I've had fuse box problems (one dipped headlight fuse connector broke and when I moved the whole box to check the starter wouldn't work so I've had to temp "hot wire" direct to ignition switch). I've since obtained a good secondhand fuse box but have yet to fit.
I haven't checked (it's 2 am and only just thought of it !) but wonder if the inlet pre heater might be affected. Would that not working alter emmisions when engine already hot ?
Thanks.
Paul Humphries.
Mileage is approx 128,000 miles
This is the third year running.
First year tickover was too unstable to test so I ended up replacing Piersburg with brand new Weber twin choke carb (manaul choke). It was a proper kit for an auto with the solenoid vac valve to alter timing when gear selected. The MOT tester said the emmisions were perfect "straight from box" and didn't need any adjustment to gain pass.
Soon after the rubber base split so that was changed.
Last year emmisions were too high so I adjusted them with my Gunson Gastester but didn't get them down far enough so tester tweaked it the required 3% needed to get a pass. I assumed the split base might have been the cause for gaining a pass when first fitted due to air leak and didn't worry about it needing adjustment
This year they are back up to over 6% with sky high hydrocarbons.
The car is in good condition with recent new plugs of the proper three pronged type. The plugs are black and dry indicating rich mixture.
I thought it would be something simple like sticking choke or blocked air filter but they are both OK.
BTW the engine breather ISN'T currently connected to the air filter box so that cann't be affetcing emmisions. The Weber conversion means the pipe wasn't long enough and I've never got around to doing anything about is as no fumes .
Anybody ideas what can be wrong ?
I should add I've had fuse box problems (one dipped headlight fuse connector broke and when I moved the whole box to check the starter wouldn't work so I've had to temp "hot wire" direct to ignition switch). I've since obtained a good secondhand fuse box but have yet to fit.
I haven't checked (it's 2 am and only just thought of it !) but wonder if the inlet pre heater might be affected. Would that not working alter emmisions when engine already hot ?
Thanks.
Paul Humphries.