Does anyone know a way to measure the exhaust emissions of a petrol car at home? A semi sensibly priced machine I'm guessing. I've got a Gunson gastester but it's always been a bit toffee at the best of times and even then it'll only measure CO and not hydrocarbons and whatever else they measure. It's something I've wanted to be able to do for a while but a recent MOT failure on emissions of the Discovery has sort of prompted me to try and look into it again. It's one of the few areas where I can't check the results of my work myself and know that when it rolls back out of the garage it's fixed. I'm going to fix what I think the problem is and then have to take it back to the garage before I find out if I've fixed it or if there's another problem I've got to chase down - a bit more trial and error than I'm happy with. One of the problems with more modern vehicles I suppose (yeah yeah it's 23 years old). It runs fine and there's no visible smoke but I think one of the cats has broken up resulting in the failure. I've thought of a lambda sensor and some wiring but they are an oxygen sensor if I remember rightly?