Technical Solved problem high and erratic rpm Brava 1.6 16V

[Corvinus]

For all the guys who are looking for resolving problem with high and erratic rpm problems, i solved mine.
I had a problem when starting cold, the rpm's stood up to 3000, and when it tryied to get low it getted up right away. And in idle after the engine was up to functioning temp the rpm's didn't go lower then 1000-1200 revs.

I solved this by changing the TDC/RPM sensor on the crankshaft, cleaned the throttle body, cleaned also the idle speed actuator and an ECU reset (i believe althought it was the tdc/rpm sensor, the cleaning was additional). Worked on my Fiat Brava 1.6 16V year 1996.
Now the rpm's don't go upper then 1500 revs (very cold start) and come down to 800-900 revs after about 5 min of driving.

So hope this helps someone .

 

[fiat37]

Hi, I think RPM was not problem in your case. Cleaning throttle body and IACV helps to cure erratic idling in most cases. RPM sensor is incorrectly gaped in most cases, or its connector is corroded.

 

[Corvinus]

It was the sensor, and why do i say that because the first thing i did when the problem appeared was to clean the throttle body, the actuator and basically every sensor on the intake manifold (didn't worked). The gap of the sensor mounting did not changed, cause it was firmly tight and worked till the sensor has gone bad.

So i'm sure that it was the sensor.

 

[cpt_spalding]

A similar problem just manifested on my 1.2 16V SX (2000) Brava.

When warm, the engine seems to want to idle at about 2000rpm then often drops to 1500Krpm, sometimes not. If I release the clutch a little then let it idle again it will come down to 1200rpm.

I think I'm also hearing a slight blow from the front of the exhaust altho I've not had a chance to properly investigate anything yet.

Not got a Haynes manual yet, so if some1 could point me to the IACV (is this the same as the idle speed actuator mentioned above?), & the throttle body for cleaning, I'd be obliged. Maybe there's a sticky guide for this somewheres?

This appeared last night. Up until then I had noticed the revs could dip down to a low 700rpm & it even cut out once or twice. The car's new to me since last weekend when I had to scrap my Mondeo.

All help & advice appreciated.

 

[Adrian Bravo]

Hi CPT
On the 1.2 idle is controlled by an electric motor on the throttle body, the unit is black seen here highlighted in red (thanks to m205b for the image)

The 1.2s idle control motor can cause an irratic idle, it must wear out with age. Lots of other users have fixed this by putting washers between the motor and throttle body. Two of the bolts fitted with washers are highlighted in green in the picture.

Any air leaks in the inlet manifold would cause an irratic idle aswell.

 

[cpt_spalding]

Thanks, that looks pretty clear. However as an engineer, I'm struggling as to why the simple addition of washers there would affect the operation of the motor.

I'm not doubting, just wondering what the effect is.

 

[Adrian Bravo]

I have not worked on a 1.2 so I dont know why it works, I just know enough users have reported a positive result. I guess it could be releaving friction on a worn moving part, or with the shift in position something is now sitting on a fresh surface rather than a worn surface.

 

[cpt_spalding]

Thanks.

Actually i just found m20b25's sticky in the guides. It tells me everything I need to know there