Erratic idle and MISSFIRE!!!

[Marcelo]

My 1.6 16v Brava started to have erratic idle and missfires at strat up, but when warming up engine starts to have a normal behavior.
Passing weeks, missfires did not go away, neither with hot engine. The car also starts to have problems acelerating, when pressing acelerator at first nothing happend, and little by little the engine respond. The fiat scanner test: every thing OK.
Change candels, and make an injector clenning with ultra sound. So the car return to a "normal" behavior, but little missfires didn't go away.
But now, 1 month later, the situation is worst. When start engine the whole car shakes and the engine seems to go on 3 cilynders. The fiat test until gives an OK, but fiat garage wants to investigate ($$$).
I think the injectors must be replaced, because when cleaning them the car returned to "normal".
Anyone knows what could be? I don't trust this fiat guys and they told me many alternatives to the problem....

 

[Marcelo]

One more detail. Injector warning light is off on dash. In fact, every thing seems to be "normal" except the engine behavior.

 

[Tom]

New plug leads.

 

[Mike]

It could be your leads and plugs as Tom suggests, but don't take it as definite. It could still be an injector (or more) on the way out.
Your best bet is to whip off the upper inlet manifold and test the resistance on each of the injectors. New ones should read about 15 Ohms with ones on the way out returning anything from 11-0 Ohms.
Check out the guide on this site if you need instructions.
Hope this helps

 

[Marcelo]

Thank you for your information.
2 days until fiat garage appointment. So, one more think I forgot to tell you, is that when I push the engine, let's say to 5.000 rpm (with car stoped), i can't ear the missfire but lots of black smoke cames out... could it be no burned fuel? So, does this detail tell us something abou the possible problem?

Thanks.