Technical Fiat Punto 1242 1999 Fast idle & revs up on its own accord to 3000rpm

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Technical Fiat Punto 1242 1999 Fast idle & revs up on its own accord to 3000rpm

Nobler

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May 9, 2006
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Hi everyone, I'm a newbie and didn't know this kind of place existed until I started to search the web about the problem with my wifes car.
Can anyone help?
A while ago the cars idle speed went up to about 1500 rpm. Now whist standing still its idle speed is not steady. It fluctuates between about 1300 to1700 rm. After a while the speed slowly increases to anything between 2500 and 3000 rpm. A quick flick of the gas pedal causes the speed to drop back to 1500 where it then continues to hover between 1300 & 1700rpm. After a short while the process repeats its self. Letting up the cluth to apply drag slows the speed down, when drag is removed, the engine returns to the fast speed.
The garage has charged over £200 (which included interim service) to replace the lambda sensor and temp switch which has made no difference.
They now want to replace something called the "Single Point Injector Stepper Motor" at a cost of £110 for parts.
Does this diagnosis sound correct?
Is there any way I can test/clean it my-self? I have some electronic and auto experience, but I'm the first to admit that I'm not an engineer by any stretch of the imagination.
I don't want to throw another £100+ labour down the drain.
If the diagnosis sounds reasonable, can anyone recommend a supplier on the internet that would be cheaper than a main dealer? Perhaps second hand part.
thanks in advance,
Robert
 
I have had the same problem mine was down to thecoolant temp senser on the inlet manifold has a 2 wire conecter on it this controls fueling and stepper motor it is 19mm just need a deep socket 4 inch exstension and a small ratchet being very carefull not to over tighten i used a fueltemp sensor from a t5 vw petrol 3mm longer but the same temp range ps i have been in the motor trade for 38 years and tested the car with a bosch diagnoses unit with a scope to test performance it won't show up with a standard test
 
When you disconect the ect it defaults to a cold engine and richens up and increases the rpm this not to be confused with the temp gauge sensor on the head as i said replaced a faulty one on my punto 75 now runs great so it was the problem with mine the black wire is linked to the aps tp ats and signals the ecu plus with a air leak just get the emissions checked and see what the lamda reads but really an air leak should be easy to find on the 8 valve engine i have been working on fords for the last 26 years at a main dealer my punto is a joy to work on loads of room and basic mine is a 98 vehicle one owner 17.000 miles done a clutch cambelt and water pump new coolant and a service very pleased with car suprised how quick it is
 
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id put money on it being a seized or stiff throttle body. Get some carb cleaner and give it a good clean it doesnt cost anything and is easy to do
 
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