Fiat Punto 55 SX 1996 Idle revs

[alistairsmith]

Hi All,
I have a Punto which, when the engine is warmed up, revs up and down when it is supposed to be idling. Sometimes it revs up to 3500 rpm, but stops when I tap the accelerator with my foot. I doesn't do it when I am moving.
Any Ideas or solutions are very welcome.
Alistair

 

[Nelsky]

Hello there, did you find a cure for this yet.

I have a 1995 fiat punto 55s, it just started this today. Drove the long trip to my uni, then on way home when car was supposed to be idling it was revving up and down, sometimes excessively high revs, until I touched acceelerator then it seemed fine.

Was so bad when stationary at lights had to turn engine off.

Also strangely, but may not be linked on way home I decided to put aircon on, then when i turned it off, it remained blowing.

I have googled this problem and there seems to be a few possibilities. Such as a vacuum leak, from headgasket (apparently worst case).
The idle control valve, clean with carb cleaner.
throttle position sensor.Check coolant levels and mix.
And finally the most common response was to reset the ECU by disconnecting the battery for a little while and reconnecting, apparently the ECU will then re map itself. ( when disconnecting the battery make sure you have you're radio code if required).

I am no expert and only relay information but I am definitely going to try this step tomorrow will post the results.

 

[Belle427]

if it corrects when you tap the pedal with your foot id be looking at the throttle position sensor

 

[Nelsky]

aint had chance to look yet, but the car did seem to drive ok, it was as soon as I took my foot off accelerator at junctions/lights it started up down revving, If i left it at idle eventually the revs went up really high, i darent leave it to see how how long for, worried it might blow somat else.

 

[alistairsmith]

Hi All,
Many thanks for the replies, which has given me a few ideas. I still haven't sorted the problem yet, but at least I have some ammo to use now.
Regards Alistair.

 

[Nelsky]

Just thought i'd share that I checked my coolant and also disconnected the battery for a few hours to see if this helped. But had absolutely no effect at all. Car is exactly the same. GUTTED

 

[^neo^]

If the revs are hunting then the first thing to swap is the coolant temp sensor. If it's giving a duff reading to the ecu it will be overfuelling and underfuelling all the time (causing the revs to hunt).
Disconnecting the battery may well have reset the ecu, but if the sensor is shafted then the ecu will pick up on this almost instantly.
They're not expensive, and usually in a nice easy position to change (unless you own a ford!)