High idle problem on 2.0 20v VIS engine

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High idle problem on 2.0 20v VIS engine

Cona

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Joined
Mar 13, 2008
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Hello dear members,

I am driving 1999 Fiat Coupe 20v VIS 154 hp.
Two days ago, I have cleaned throttle body and MAF sensor
because the car turned off on stopping.

After reasembling the parts, revs are on 1050 rpm on idle.
Sometimes they go up to 2000 rpm and then go back to 1050 rpm.

I have changed the ECU temp sensor, and tried with new Bosch MAF,
but nothing makes difference. I also reseted ECU, and that also
didn't help.

I have sealed the NRV (non return valve, that has little spring - it is located after the throotle body on intake manifold), and revs go down only by 50 rpm.

There is no false air that engine is sucking, also there is no vacum present when oil filler cap is removed.

I have double checked everything.

Any idea?
 
Last edited:
Problem solved thanks to guys from Fiat coupe forum!

Removing the spring in NRV fixed the problem.
 
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