Technical fuel pressure

[serhioje]

Hi there. I have a rough idle on Fiat 500 2014 1.2 petrol (manual gearbox). One of the things I suspect is fuel pressure as some fuel pumps specifications say it should be 4bar meanhile others say 3.5bar. I tested fuel pressure and got 3.5bar but concerned if there is a decline and it fell from 4 to 3.5 just by coincendance. Cylinders compression test is ok (from 13 to 14 bar, cold engine )

Question : what is the fuel pressure on the similar car with no rough idle issue?

PS spark plugs, coil pack, ignition leads, oxygen sensor, were replaced for new. Also tried another used throttle body with no effect.

 

[steveras57]

Changing the fuel injectors cured my problem!.
Aare your symptoms lumpy idle but tacho reads steady around 800rpm ,with a stumbling feeling which you can feel through the base of the seat as a vibration?

 

[serhioje]

Changing the fuel injectors cured my problem!.
Aare your symptoms lumpy idle but tacho reads steady around 800rpm ,with a stumbling feeling which you can feel through the base of the seat as a vibration?

Yep, the symptoms are absolutely the same. However I checked the injectors and they looks pretty fine. I was thinking about this as well but would like to ensure first that fuel and oil pressures are ok(as oil pressure drives camshaft adjuster)

 

[The Panda Nut]

Clean the MAP sensor. They dont seem to need much to knock them off and tickover is the first thng to go off. Leed tside of the intalke manifi=old as you look at it.

 

[serhioje]

Clean the MAP sensor. They dont seem to need much to knock them off and tickover is the first thng to go off. Leed tside of the intalke manifi=old as you look at it.

I'll try today. Is there something specific about cleaning?

 

[steveras57]

best to use a dedicated map sensor cleaner spray as its uses safe chemicals and wont contaminate the sensor probe! other sprays like carb or brake cleaner might ruin your sensor!! or you could try just wiping it out with a clean cloth and or cotton bud etc!.

 

[The Panda Nut]

Well I just wipe very gently with perfectly clean lint free cotton. I actually remove the throttle body and do the inside of the manifold as well. Oil from crankcase breather causes me problems. My car has donE 80000 miles. it had done bad idling and bad stuttering on first driving off. Crank case breather hose was splitting last time I did it so replaced that too. I thought tge engine had severe problems but this restored normal working. I am considering a repacement map. Cleaning the VVT solenoid also helped restore performance. I gave a quick squirt with carb cleaner and refitted. The difference was very apparent. Changing plugs is also helpful, thet dont ladt long at all in this car. I saw a message in MES also thay said change oil after only 6000 miles. So I suspect blow by is affecting crak pressure and MAP. Once all done it goes a year before demanding service again. Normal running is very good.

 

[serhioje]

Well I just wipe very gently with perfectly clean lint free cotton. I actually remove the throttle body and do the inside of the manifold as well. Oil from crankcase breather causes me problems. My car has donE 80000 miles. it had done bad idling and bad stuttering on first driving off. Crank case breather hose was splitting last time I did it so replaced that too. I thought tge engine had severe problems but this restored normal working. I am considering a repacement map. Cleaning the VVT solenoid also helped restore performance. I gave a quick squirt with carb cleaner and refitted. The difference was very apparent. Changing plugs is also helpful, thet dont ladt long at all in this car. I saw a message in MES also thay said change oil after only 6000 miles. So I suspect blow by is affecting crak pressure and MAP. Once all done it goes a year before demanding service again. Normal running is very good.

Thanks, I cleaned the throttle body and even tried to relace it (with no effect), the crankcase breather hose is ok, oil was replaced 500 miles ago. VVT solenoid was cleaned the same time.