Technical rough idle

[rich sweeney]

My fiat seicento sporting 1.1 SPI has started to run rough at idle. I bought the car knowing that the exhaust is blowing badly at the flexible section on the downpipe but not sure if this is related to rough running ?

previously when it had done this i changed the spark plugs and it sorted it out immediately. Now it is running rough i removed the spark plugs and they have a small amount a white over all of them which i assume means its running to lean?

The plugs in it are NGK BCP R6E.

Could the exhaust leak cause the car to run lean ?

any help much appreciated

 

[fingers99]

I'd replace the buggered section of the exhaust before anything else.

But do the old "run it at night, open the bonnet, look for blue flashes", trick.

 

[rich sweeney]

bought new downpipe and the rest of the exhaust as it was knackered.Loads of back pressure now but the slightly lumpy running is still there , spark plugs still seem to get sooty and so i think its fueling causing the slightly lumpy idle.
Any ideas ? maybe a coolant sensor or is there a sensor on the spi unit

 

[jimbro1000]

Check the pipe to your MAP sensor from the engine - a classic cause of the problem you are describing.

 

[marino]

This may sound sill but give the face of the crank sensor a clean, this is normally overlooked or forgotten about,because of it's position low down it gets gunged up, use paper towel or something similar as the gap between it and the crank pulley is small, it worked for me, ticks over smoother pull and runs better all round.

 

[rich sweeney]

cheers for the replys , i will give the map sensor a clean as its an easy job.

when i got the car the vacuum pipe for map sensor was disconnected completely as the vacuum pipe was missing. i replaced it with some clear rubber tubing but this was flimsy and may colapse under a vacuum?

also someone has previously tampered with the wires going into the sensor on the side of the spi unit. they have put a wire from this plug back to the plug on the ecu for some weird reason. will get picture up

 

[fingers99]

Get the manual from the downloads section and check both. Don't clean the sensor itself, but do get the correct pipe and fittings. (If scrappy, any Cinq, Punto 55, Punto 60, SPI Sei).

 

[rich sweeney]

mento to say clean the crank sensor ! and because i live in guernsey there are no scrap yards or breakers so going will just buy some better tubing.