Technical Uno Turbo semi-warm idle problem - SOLVED at last

[alexGS]

For as long as I can remember, my Uno Turbo has always had a problem (particularly in the winter) with the engine not idling shortly after starting off.

It would always start and fast-idle (about 1200RPM) when cold, then by the end of my road I would see the familiar red lights - engage the clutch in third and bump-start, and so on for the next two stops. Now that it's winter, it even did this at the end of the 1.5km straight road that you drive along to get to anywhere from my place. This was annoying... particularly as once the temperature was up to usual (70-80 degrees) the idling was perfect.

I had spent some time tweaking the throttle opening/idle speed screw/mixture screw to get the hot idling nice and steady. I found that having the throttle cracked open and the idle bypass screw closed tended to prevent the engine dying as revs returned to idle (when hot). But nothing seemed to solve the semi-warm idle problem. When I bought the Uno Turbo four years ago, the hot-idle speed was jacked up to 1500RPM, no doubt as a kind of solution, but this made gearchanges difficult.

Anyway the culprit was the auxiliary air valve (pictured, happily it was this clean when it came off the engine!). It had the correct-sized 'hole' when cold, but then when heated electrically it was closing off too early. I got a spare (from SteveNZ) about a year ago, finally gave it a scrub-up this evening and fitted it. The idle speed was a bit slow when the engine was first started (about 900RPM) but then happily it stayed just over 1000RPM during the first four stops, and on reaching my destination (engine hot) the idle was the correct 900RPM. Fixed at last

-Alex

 

[F R O S T Y]

Oh come on Alex even i could have told you it was that!!! hehe Its the supplementary air valve, its meant to allow more air to flow through when the engine is cold, a common fault i replaced mine a while ago due to having the same problem, tried endless times adjusting the idle speed etc with no luck but then i traced it down to this. Got a new one, switched it over and now she runs fine...well she does for now anyway lol

F R O $ T Y

 

[alexGS]

Oh come on Alex even i could have told you it was that!!! hehe Its the supplementary air valve, its meant to allow more air to flow through when the engine is cold, a common fault i replaced mine a while ago due to having the same problem...

Yes I remember, I think I suggested that you should replace it

You have to admit though, it's pretty strange for something electrical to work *too* well, in other words it's supposed to close gradually as the electric element heats it up, and then it stays closed due to heat from the cylinder head to which it's bolted. Mine would start off fully-open (I can see the hole through it when it's cold) but then for some strange reason it closed too early, before the engine had warmed enough. The replacement closes more slowly. Generally this Bosch stuff is pretty reliable - I mean, it's nearly 20 years old, so I think I can forgive it!

-Alex

 

[F R O S T Y]

Yes I remember, I think I suggested that you should replace it

You have to admit though, it's pretty strange for something electrical to work *too* well, in other words it's supposed to close gradually as the electric element heats it up, and then it stays closed due to heat from the cylinder head to which it's bolted. Mine would start off fully-open (I can see the hole through it when it's cold) but then for some strange reason it closed too early, before the engine had warmed enough. The replacement closes more slowly. Generally this Bosch stuff is pretty reliable - I mean, it's nearly 20 years old, so I think I can forgive it!

-Alex

Oh yeh you did tell me that didnt you lol Cheeky git!!!
My car would idle nicely at 1000rpm steadily on start up but then it would bounce erraticly once the temps got to about a quarter way up. It would hold the revs at about 1500rpm for a while then drop back down to 1000rpm and keep doing this until the temp reached normal where it would settle again back down to 1000rpm. Really used to bug me

F R O $ T Y

 

[oldskoolmk1unoturbo]

i need a new one of them for mine, mine is sticking, it sometimes idles at 1500 or 800rpm and when its warming up the revs bounce up and down til its warmed up.

any idea on how much they are new frosty?

 

[F R O S T Y]

i need a new one of them for mine, mine is sticking, it sometimes idles at 1500 or 800rpm and when its warming up the revs bounce up and down til its warmed up.

any idea on how much they are new frosty?

Hmmmm... I meant to say i swapped it over with a second hand one i had, not sure how much they are new to be honest mate, Do you think that they are they still available?

F R O $ T Y

 

[custard]

ah the 1.8 mk 2 cavaliers used the same set up so maybe VX could supply one if not fiat?

 

[SteveNZ]

Alex, the aux air valves are common on all Bosch injections systems of that era. Maybe it had been replaced with one from a different car, soemthing that warms up more quickley. Uno turbo's generally take a while to warm up.

Or, is there some kind of spring in it thats gone weak?

Interestingly, ive never had an idle problem with my mk1 even though the valve was not even bolted onto the head. My Tipo on the other hand, with its "superior" ecu controlled idle control valve, is terrible! Its never run right.

 

[Biz]

I think i can find out frosty mate!

Southern Carbs near me do BOSCH parts

Mine idles at 1,000rpm when at operating tempreture, i think the SAV is being a tit!