Technical Spark advance unstable at idel

[Moeinc88]

Hi, I have a rough idle on my 1.2 engine. I plugged to multiscan, no codes only thing I noticed is the spark advance jumps around, between 3 degrees and 14 degrees at idle. I'd expect it to be more or less stable, could this be idle problem? Or is it suppose to be like this

 

[koalar]

Your looking at a symptom not the cause. The ECU can adjust the advance due to feed back from it sensors

Rough idle points it a misfire probably more than one cylinder

I would start the car with the injector to cylinder one disconnect assuming your car has multi point injection

And see if the rough idle is worse or the same then reconnect the injector

Then do the same for the other cylinders

If your car has single point injection or carburettor you can do the same by removing each HT lead in turn

 

[Moeinc88]

Thanks for your reply. So I disconnected each injector one by one. With each one its the same the rough idle actually stabilizes if I disconnect an injector, so instead of the random roughness , if I disconnect an injector it still rough but not random, sounds more like a truck

 

[koalar]

not what I was expecting

When you say rough idle

Revs going up and down
Or
Engine shaking

Any performance issues accelerating

Any banging noises when cold

 

[Moeinc88]

Engine shaking,alot. drives well though. I had an issue with my timing sprocket few months ago,the key stripped so sprocket had too much play. I repaired it , it didn't take rough idle away though, so that's why I'm still suspicious of timing

 

[koalar]

i never seen one over here in the UK

Assuming the engine is the same as in the panda/punto you should be able to tell quite a lot from a compression test my car is over 200 psi some people are getting 175 psi and still fine

Down across all cylinder is likely to be timing, down across two adjacent head gasket


What upstream O2 voltage look like multiECUscan at idle and a constant 2000rpm

Before you start the car does the ambient temperature and pressure look right in multiECUscan

 

[Moeinc88]

I recall checking o2 sensor values at idle, it was normal according to my knowledge. Value was jumping between 0.2v to 0.8v. What do I need to look out for at 2000rpm?

I checked air temperature and coolent temperature on a Stone cold engine a week ago and values were zero.

I checked spark plugs colour and it all looked normal ,light tan colour. 1 was a bit lighter than the rest though I noticed.

I have been trying to figure it out for months to be honest. Replaced so many parts already. I need to get directly to the problem now instead of just replacing parts.

 

[koalar]

I recall checking o2 sensor values at idle, it was normal according to my knowledge. Value was jumping between 0.2v to 0.8v. What do I need to look out for at 2000rpm?

I checked air temperature and coolent temperature on a Stone cold engine a week ago and values were zero.

I checked spark plugs colour and it all looked normal ,light tan colour. 1 was a bit lighter than the rest though I noticed.

I have been trying to figure it out for months to be honest. Replaced so many parts already. I need to get directly to the problem now instead of just replacing parts.

Here mine at idle

Fiat Panda 169/2005 High Fuel Consumption on idle/stationary | FIAT Panda (Mk3)

I am not sure of you're problem, the only thing I can tell is my experience that almost was the same. 1. Started to check every hose of the air intake to check for broken or small cuts. Checkt the intake itself for good sealing to avoid dust in the EGR. 2.Took out the EGR to check for grease or...

www.fiatforum.com

Temperatures and pressures shouldn’t be at zero unless the outside temperature happens to be zero and the cars in space

If the post cat is high at idle but fine at 2000 it would point towards a low speed misfire

 

[Moeinc88]

OK I meant the coolent temperature and the intake air temperature is the same. The pressure is atmospheric before startup, when running the pressure reads around 600kpa.

I don't have a cat, so I have just one o2 sensor. I have noticed that when I remove the vacuum pipe from map sensor and block it it idles much better. Also if I unplug 02 sensor it idles perfectly. I have replaced 02 sensor already.

 

[Moeinc88]

Sorry I meant that map sensor reading is 600mbar, not kpa