Technical Cinquecento sporting revving issue :(

[hame41]

Hi guys,
I went on a roughly 10 mile journey yesterday and noticed my car was holding its revs at about 1600 rpm and wouldnt come down whist driving,i got it home and it was still revving at about 1550 then i left it idling (for about 30 secs) then it started doing this: without me even touching the throttle.It then revved to about 3000rpm and stuck there until i turned it off. Any ideas guys? i just hope its not trying to be the next Herbie on me! thanks in advance

 

[blu73]

my first thought would be idle control valve, although its usually cheaper and quicker to get a different complete TB from scrappies and swap whole thing over than buying a new one. Added to the fact that generally you round off the bolts holding it on before they undo.

But it could just be a vacuum leak as well, check all the vac lines first & around the base of the TB. Particularly the one to the MAP. Could also try disconnecting map while its doing this to see if it has an effect, it should do obviously but if its not working right it might not make any difference, then i would be suspecting the map.

 

[hame41]

Hi Blu,thanks for the reply! I have a novitec carbon air box fitted which maybe worth a mention,but Ive had it for a while and it's never caused an issue.
I disconnected the map sensor plug and it calmed the random erratic revving but it still sat too high (1550) I had a quick look at the pipe too and it seemed okay,is there any others to check? Thanks in advance

 

[fingers99]

I'd rule out the airbox.

It'll either be one of the hoses to the TB -- can be any of them, and don't rule out the big fat servo pipe -- the bottom seal on the TB itself, or the the idle air control. Vacuum side air leak, by any other name.

 

[blu73]

there is some vacuum take off's on the back of the TB, they may or not be in use - one would normally be on the oil breather (but that might be stock with your novitec box on), another pipe there goes to the charcoal cannister (also may or not be present by now, they are not new cars afterall).

I would pull the map pipe off completely to inspect it, blow down it to confirm its not blocked, then again with one end blocked to check for leaks/splits/holes etc.

Have you had the engine management light come on or flash at all while driving/idling??