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I've been having this issue for a while, just rebuilt the engine and was hoping it would miraculously solve the issue. Start the car and idles at around 1200. After about a minute, just as the revs start to think about starting to drop, the K light comes on and the revs climb to about 1500 over a few seconds. If I rev the engine the revs fall back to 1200 ish and the k light goes off. The revs then creep back up to 1500 ish and the k light comes back on. This stays the same apart from the lower revs value goes towards 900 ish and the higher to 1100 ish as the engine warms up (so the SAD is working!). It has a new temp sensor and the lambda was new around 1200 miles ago, the AFM is a replacement but was second hand and I'm almost certain has been tampered with, I think this may be part of the problem / solution but I need to understand what's going on in the ECU's tiny mind to try and work out the solution. The only fault code is 52 (fuel mixture adjustment) now on Autodata the solution to this is to check everything!! I'm as sure as possible that there are no air leaks, I've even replaced the vapour recycling valve thingy as this is about the only purposeful introduction of unmetered air. My thoughts are that for the first minute or so while the engine is very cold the ECU just runs on a pre-set output and the lambda is ignored, then after a certain time or temperature it kicks in, and starts to try and adjust. For some reason (rich or lean?) the revs are rising as a result of this adjustment but the ECU is putting the light on as it's not able to bring emissions into line, or the results aren't fitting into the acceptable range for a given set of values. What would cause a rise in revs? idle too rich so trying to adjust leaner or the other way round?? As mentioned the Temp sensor is new so unlikely to be to blame, I think the AFM has been tampered with as there is a mark on the sprung wheel in tippex and the lid was loose when I got it but I have no idea how to go about making adjustments or knowing whether it is in fact out. I think i know that a clockwise adjustment tightens the spring which closes the flap slightly which makes the ecu think there's less air entering so reduces the fuel and leans it up?? is that right?? I'm thinking it's too lean at startup and when the lambda kicks in it's giving the signal to add more fuel which is making the revs rise at tickover but which puts the figures out of range and puts the light on!? I'm not sure where the revving of the engine making the k light go off temporarily fits in? I'm guessing I'm not going to get far without a gas analyser but is there anything I can try at home? Hope I've not twisted antones melon too much with that post,suffice to say it's certainly twisting mine!! All the best Martin

I carried out a coolant change recently and changed the standard 1Bar GTi6 radiator cap to a 1.3Bar item from Halfrauds. I was hoping it would make a difference but it really hasn't. The following pic is the vehicle up to operating temp and occurs when I'm driving steady at say 30mph and above. It pretty much stays at this point: When I park up it'll creep slowly up to the mark below, this is exactly the point upon which the second fan activates: When the second fan is blowing the temp needle drops extremely slowly, in fact it'll drop back a smudge to the second last white marker and stop blowing, only to start up again shortly after as the needle once again reaches the above point. Is this typical? I'm not losing coolant and the car drives fine. I'm aware the gauge overreads but it's butt clenchingly worrying to see a temp gauge read so high and stay in that zone until I get properly moving again. Not a very good pic (was checking battery clamps) but shows a bit of the plumbing, there's a T-Piece below the expansion tank. I'll try and dig out a better pic of the pipework if it helps. : If there's something not right I'd love to know.

Good Evening. I get the feeling that my thermostat is on the way out (I doubt it's been replaced over the last 22 years) and in any event I figure I may as well replace it, given it made a substantial difference to the performance of both of my previous vehicles and it's a doddle to do. Two questions - Firstly, as far as I am aware, the stock thermostat begins to open at 89℃. I'm thinking that it might not be such a bad idea to replace it with a slightly hotter thermostat (say 91/92℃), for the faster warm-up, higher operating temperature (possibly good for fuel economy?) and hotter heater. Any reasons why this would be a bad idea? Obviously in a modern computer-controlled car I wouldn't even think about it but in a 22 year old car with no computer it's at least an interesting idea. I know it used to be fairly common practice to change thermostats twice a year with the temperature change between seasons. Secondly - Jiggle pins; I have no idea whether the stock thermostat has one (and can't visually check it with any great ease for obvious reasons). Looking around Google it would appear the stock one doesn't have one, but most of the ones I have access to do have one; will it make a difference? I know the idea behind having one but thought I'd ask anyway. Thanks in advance for any advice! N.B. car is a 1990 205 with the carb TU3 engine, outside temperature here in New Zealand regularly goes below zero in the winter but very rarely goes north of 35℃ in the summer.