Fiat Cinquecento problems - Kate
Hi there,

I have a fiat cinquecento sporting 1997 with an intermittent problem where it stutters along the road and/or hunts on the revs - occasionally revving madly! Before I bought it it turns out it had the following parts replaced by a garage in an attempt to get rid of the problem which just wouldn't go away:
Spark plugs, HT leads, 2 map sensors, complete single point injection unit, 2 temperature sensors, crank sensor, lambda sensor, and 3 ECUs.

My Fiat dealer did a diagnostic test and recommended a new lambda probe (which I replaced). When this didn't work they took it in again and said that the computer kept telling them it was one fault and then the other (low battery voltage was a common theme). Nothing they tried actually worked so they can now only suggest that they take the car in and 'have a good look around' (at £40/hour!)


Today I had an interesting development: when the car goes into a mad revving stage it is calmed down when I remove either of the coils (but still keeps running). I was very hopeful I'd found the problem but I've replaced the coils and it's still the same! - Revving and not revving on a 30 second cycle then going into a complete mad rev after about a minute and stumbling when I drive it at low speeds (when you put your foot down on the accelerator the revs actually drop causing a flat spot and when you take your foot off they drop too)

I think I'm going to give up soon, it's looking impossible to fix. Have you any suggestions as to what it might be?
Re: Fiat Cinquecento problems - David Davies
Kate
This sounds a difficult problem to solve, but one possibility is that the car has a poor earth somewhere eg battery negative to engine block/ body/ ECU. Careful volt drop testing is needed. Another possibility is poor supply voltage via ignition switch or main management relay,which I note you do not include in your lists of parts renewed. When multiple fault codes are logged it usually means an earth or supply problem and I do not think it could be poor contact at the ECU plug if,as you say, the ECU has been renewed three times.On this matter of ECU renewal, as I understand it, the keys and locks have to be changed as well to match a new ECU. Are you telling us this has taken place 3 times? Difficult to believe. Hope you find the problem and let us know the fix.
Re: Fiat Cinquecento problems - James
Relays and associated circuits can cause strange problems. I had a fuel pump problem that turned out to be a dry joint (bad soldering) on a little circuit board inside a relay. Easy to fix, but a b- to locate!

Agree that earthing is worth checking - a loose nut on an earth post, or a dirty spade/block connector, can create havoc.
 

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