General UNO 1.1 i.e. idling problem

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General UNO 1.1 i.e. idling problem


New member
Oct 1, 2004
Hello! This is the third message I'm writing... the others desappeared! Now I'll use "copy and paste" to save my text in memory in order to avoid problems!

However... I'm new of this forum, and I'm very happy to reaching it, I think it's very very useful!
So I'll describe my problem.
If I start the engine when it's completely cold (for example after a cold night), the e.c.u. fattens the mixture and increases idling, and the engine starts promptly (it' s totally regular). The problems arrive after 2 - 3 minutes of working: as the engine starts to warming up, idling problems become evident: when I stop the car (for example at traffic light), I can clearly listen to the r.p.m. decreasing, and the engine seems to cut off. Then ecu increases throttle position and r.p.m. increases. Then after 15 minutes of hotting, the problem completely desappear. It seems a problem of poor mixture on an engine not completely hot! So I checked Lambda sensor, but it' s OK: I can see its signal to oscillating between 0.2 and 0.9 volts when I'm going on street. But when I'm at idling I see the signal quite static, and I can listen the engine r.p.m. to increase and decrease as the lambda tension increases or decreases. In particular Lambda is near 0.1 0.2 Volts when engine has idling problems. I also checked refrigerant temperature sensor and it seems OK (resistance is 2000 3000 ohms when it's cold, and it decreases to 300 ohm at hot). I also changed vacuum advance. Then I regulated position very advanced: I think it' s ok because I can't listen to "striking in head". I can't increase advance because engine 'd start to "strike in head" when I relase accelerator at slow enough r.p.m.
This is my problem... does someone can help me?
Thanks a lot dear!
i used to have similar probs in my old uno 1.0

used to be a pain in the arse to start just on the key even though it would start first time and straight away... only thing is that it would turn on and then sit at an extremely low rev (as if stalling itself) for a minute or 2... if u tried to help it out my pressing the throttle it would just cut out and then would refuse to start for 5 mins... really weird... but if u put ur foot about 2cms down on the throttle and then turned the key it would start up perfect and have no probs!

ok... its not quite the same prob heh but my uno did have erattic reving when idling... reving up and down all the time (sometimes getting really really low) and sometimes it would cut out at lights for no reason (well, it reved itself too low and stalled)... i never got to the bottom of the problem and sold the car and got a cinq (not because of the problem).

a number of people suggested that i replace the vacume advance unit. might be a good idea for you to try

edit: just read tjhat u already have tried that :) hmm, i cant really think of anything else... i never really tried to combat the problem whenb i had my uno, i just left it as a character of the car hehe
Make sure the accelerator cable is slack/loose enough so it strikes the "idle-plunger" on the back of the SPi (carb) when you let your foot off the gas. My Uno stopped on every red light if I didn´t hold the pedal down a couple of cm´es and held the car on the hand brake. Very annoying - it could stall when travelling down a highway doing 100 kmph if I let my foot off the gas. It was very interesting to do a hill-start on the highway... Also CLEAN the SPi, remove the oil breather hose and clean it. Pull out the brass filter (flame prevention) inside and clean out old oil deposits so the engine can breathe.

OK. I' ll try to clean SPI and the other stuff! However, I underline that the problem is only during the first 10 - 15 minutes of working (and NOT during the first minute, when engine is completely cold). So I think it's a carburation problem! Accelerator cable is OK. Do you know if Mono Jetronic works in "closed loop" also at idle? My lambda signal is quite static at idle! It seems that ECU is ignoring Lambda at idle. Andrea.
Not the old vacuum advance problem that I myself had and seems has been the cause of others problems is it?
I tried to change the advance: if I increase it, the idle problem seems to be reduced. Perhaps the increased advance creates problems when I relase gas at low RPM: infact engine seems to have problems (I can't explain it clearly in English): it seems to "tear" but I'm not sure it's the correct word. However I need to push the clutch or push the gas to stop the problem. So:
1) increasing advance eliminates the idle problem, but creates a new problem, probably due to an excess of advance;
2) Lambda signal is approx 0.1 V (poor mixture?) during idle problems.
I could chech engine and air sensors: I know they are resistors, does anyone know what type of values I'd find on them at cold and at hot? And what about thermostatic valve in air filter? It seems that it's closed from hot intake (that one that comes from the heating on the stock-pot), and it's open from cold intake.
Let e know if someone has some ideas, and very sorry for my English!
Thanks a lot,