I am so confused with my issue. My 1.6 Petrol engined FIAT Palio Adventure sticks to higher rpm of 1100 (instead of normal 650) after bumper to bumper traffic for a few minutes. THe car runs normal on highways and idles perfectly.

But when ever i enter bumnper to bumper traffic the idle rpm shifts to 1100 mark and stays like that until i restart the engine.

Can anyone help me. Please.

I have tried changing the following parts,

- Throttle Body
- ECU
- Pressure sensor
- rpm sensor
- ignition coil

some one Please help me. What could be the problem.:bang:

leave the car in peace . it is normal . the ECU and Body C will ever control the idle every time when the bateryy has to charged or current consumption is raised by fans lights, a/c,... .

I don't think it's considered to be normal behavior, at least our 1,6 Palio doesn't idle like that.....

Well these are the updates. Tried simmulating the stop-go traffic by parking on a small incline and accelerating and stopping. After around 10-15 acceleratins and stopping moves i find the rpm slowly sticks to 1100 mark.

Could it be that petrol being pumped while accelerating is not being fully used and the excess fuel slowly builds pressure increasing the rpm?? Please help

gemithomas said:

Well these are the updates. Tried simmulating the stop-go traffic by parking on a small incline and accelerating and stopping. After around 10-15 acceleratins and stopping moves i find the rpm slowly sticks to 1100 mark.

Could it be that petrol being pumped while accelerating is not being fully used and the excess fuel slowly builds pressure increasing the rpm?? Please help

Click to expand...

No. The fuel pump recirculates fuel all the time, and engine uses as much as it needs, while the rest gets recirculated back to reservoir.

Agree,
I think something else is wrong.
I suspect a small electrical device that controls idle is not working well, or maybe it's dirty, happens a lot.
I honestly don't know the English name for it (remember, I'm Dutch), we call it "stappenmotor".
Sometimes, when using low quality fuel, it gets stuck, and causes the problems you describe.
Did you contact a fiat dealer about this?
Did you have your ECU read for stored problems?

Maybe a good fuel injection cleaner will help.

Green said:

No. The fuel pump recirculates fuel all the time, and engine uses as much as it needs, while the rest gets recirculated back to reservoir.

Click to expand...

Thanks for the fast reply. What if the recirculation is not happening properly. Will this cause such a thing. Just thinking.

gemithomas said:

Thanks for the fast reply. What if the recirculation is not happening properly. Will this cause such a thing. Just thinking.

Click to expand...

Peter Pick-Up said:

Agree,
I think something else is wrong.
I suspect a small electrical device that controls idle is not working well, or maybe it's dirty, happens a lot.
I honestly don't know the English name for it (remember, I'm Dutch), we call it "stappenmotor".
Sometimes, when using low quality fuel, it gets stuck, and causes the problems you describe.
Did you contact a fiat dealer about this?
Did you have your ECU read for stored problems?

Maybe a good fuel injection cleaner will help.

Click to expand...

Thanks. Its called a Stepper Motor. In this version its fixed to the throttle body. We have changed the throttle body. Thereby changing the Stepper motor and throttle position sensor that is fixed to the throttle body.

HAve been talking to FIAT guys in india. They have no clue. No error on analyser.

Is there anything else that switches on and off while accelerating . Something that could possibly get stuck. Or some pressure build up that could lead to highr rpm?

gemithomas said:

Thanks for the fast reply. What if the recirculation is not happening properly. Will this cause such a thing. Just thinking.

Click to expand...

Then the pump would stall, and eventually burn out from overheating, it's cooled by fuel circulation. And the car would absolutely not work. There is a pressure regulator in the system, and if it somehow went bad as to raise the pressure - it might cause black ehxaust smoke, damaged spark plugs, higher consupmtion of the fuel, but not elevated idle.

Green said:

Then the pump would stall, and eventually burn out from overheating, it's cooled by fuel circulation. And the car would absolutely not work. There is a pressure regulator in the system, and if it somehow went bad as to raise the pressure - it might cause black ehxaust smoke, damaged spar plugs, more consupmtion of the fuel, but not elevated idle.

Click to expand...

That leaves me even more confused now. Well. cant really figure out what is causing this

Accelerate-Stop car- Accelerate. Repeat for 10-15 times and we have the rpm stick to higher range.:bang: Turn off car and start immediately and you have a smooth running car till the above step is repeated. Any logic???

Only logic I see is that somehow the ECU is programmed for stop n go driving and that it raises idle when it recgonizes such conditions. Why would it do that I have no clue - maybe to preserve battery charge, since it is a situation where charging is impaired due to low engine rpm...? Really, there is no fault that could produce these symptoms that I could think of..only logic points to ECU being programmed to do that.

Green said:

Only logic I see is that somehow the ECU is programmed for stop n go driving and that it raises idle when it recgonizes such conditions. Why would it do that I have no clue - maybe to preserve battery charge, since it is a situation where charging is impaired due to low engine rpm...? Really, there is no fault that could produce these symptoms that I could think of..only logic points to ECU being programmed to do that.

Click to expand...

Could t be that the alternator is not working properly and the ecu is compensating by increasing the revs.

No way, the Palio is a very basic car, with a very basic ECU, it doesn't recognize the conditions you describe at all.
I suspect something very simple, like a stuck cable or something.
I noticed with our Palio 1,6-16V it reacts very sensitive on fuel quality, since then I only use Shell V-Power fuel, everything runs very smoothly since 8 years and 105.000KM's...
What kind of fuel and what grade are you using?

I used to have the same problem in my Fiat Petra, showed it to the service center guys but they could not figure it out

I then started using better quality fuel, in India HP Power, BP Speed and other high grade fuels. This fixed my problem, has'nt repeated itself in the last year. So I guess its got something to do with adultered fuel

Mchulet, what's a Fiat Petra,please..??

OK, the Fiat Petra is the Fiat Siena in other countrys!!

Solved

Ok. Sorry for the long time before i could post this. I have got the issue solved after quite a lot of experimentation. Afer changing almost all sensors that we got our hands on we finally decided to change 3 things.
1. THe alternator
2. THe catalytic COnverter
3. THe Lambda/Oxygen Sensor

Ever since the problem has been solved. I seriously belive that the culprit was the lambd sensor. A faulty sensor must have caused the ECU to give in a wrong air mixture. Thus increasing the rpm.

Thanks a lot guys for all your help.