davemar 16 Posted February 18, 2008 Just taken the car (205 Mi16 with 8v Jetronic ECU) for it's MOT and it failed badly on the emissions, among other things. The CO reading was 9.5% and the HC was way above 2000ppm. I checked over with my (not very trusty!) Gunson's emission probe a couple of weeks ago and it was claiming around 2% CO. Since then I have jiggled around with some of the wiring due to random engine cut-outs (poor connections somewhere); so there is a possibility of a poor connection somewhere. My first suspect is the coolant temperature sensor, and whether that's giving daft values. Does anyone know what resistances I should get when the engine is hot and cold? I suppose another suspect is the AFM, but beyond that I'm struggling to think of things to check. The high HC reading is bit more of a concern, what could cause that? Share this post Link to post Share on other sites
Mikey S 29 1 Cars Posted February 18, 2008 Just taken the car (205 Mi16 with 8v Jetronic ECU) for it's MOT and it failed badly on the emissions, among other things. The CO reading was 9.5% and the HC was way above 2000ppm. I checked over with my (not very trusty!) Gunson's emission probe a couple of weeks ago and it was claiming around 2% CO. Since then I have jiggled around with some of the wiring due to random engine cut-outs (poor connections somewhere); so there is a possibility of a poor connection somewhere. My first suspect is the coolant temperature sensor, and whether that's giving daft values. Does anyone know what resistances I should get when the engine is hot and cold? I suppose another suspect is the AFM, but beyond that I'm struggling to think of things to check. The high HC reading is bit more of a concern, what could cause that? did the garage say that they had triedto ajust the mixture at all? if they did and it didnt move, it would point at a faulty afm. hc is too high due to the co being way too rich. it should drop when the co drops. mike Share this post Link to post Share on other sites
davemar 16 Posted February 19, 2008 I don't think they tried to adjust it. If it was a 1% over I think they may have had a go, but as it was so far over they didn't bother. Share this post Link to post Share on other sites
davemar 16 Posted February 19, 2008 I measured it again tonight on my Gunsons Gastester, and it read 7.8%, so consistant with the MOT reading. The screw on the AFM was wound right in, so I wound it out and managed to get a reading of 3.0%, so hopefully that'll be OK. The temperature sensor was reading about 900 ohms when warm, so it seems OK. Has anyone else here got a Gunsons Gastester? I can't seem to adjust mine down to 2.0% in fresh air to get the starting point. It goes about as low a 2.6%, but does vary from day to day. Anyone else had this problem? Share this post Link to post Share on other sites
205007 12 Posted February 19, 2008 i thought co on mot was 2.5% but might be wrong easiest way to change it is the spring inside the AFM Share this post Link to post Share on other sites
davemar 16 Posted February 20, 2008 i thought co on mot was 2.5% but might be wrongeasiest way to change it is the spring inside the AFM The limit is 3.5% CO and 1200ppm HC. I did adjust the spring in the past and might tweak it a little just to knock a few more 0.1% off. Share this post Link to post Share on other sites
j_turnell 137 3 Cars Posted February 20, 2008 3% is still a little high, if you can get it to nearer 2% that would be better, although still within the limits. Share this post Link to post Share on other sites
Super Josh 4 Posted February 20, 2008 Has anyone else here got a Gunsons Gastester? I can't seem to adjust mine down to 2.0% in fresh air to get the starting point. It goes about as low a 2.6%, but does vary from day to day. Anyone else had this problem? Do you have the Analogue or Digital model? I have both and prefer the Analogue model, mine adjusts to 2% no problem. Do you have it far away from the exhaust when you are trying to adjust it? So that it is seeing fresh air. Josh Share this post Link to post Share on other sites
davemar 16 Posted February 20, 2008 Do you have the Analogue or Digital model? I have both and prefer the Analogue model, mine adjusts to 2% no problem. Do you have it far away from the exhaust when you are trying to adjust it? So that it is seeing fresh air.Josh It's the digital version. Analogue is often better when you want to see variations in a signal, digital is fine with non-varying signals. The car was in the garage with the exhaust facing out, and the probe a metre or so away to the side; though this was before the car was started. I suppose there could be a lingering cloud of CO in the air. I ought to try it completely out in the open. Share this post Link to post Share on other sites
C_W 3 1 Cars Posted February 20, 2008 They don't run brilliantly on the 8v Jetronic injection, I found idling to be one of the problems when I ran mine temporarily on it. I think the more efficient 16v engine affects things. I ended up using an ecotek valve to bleed air at idle and low revs! Share this post Link to post Share on other sites
