(T) 500 spluttering on acceleration, start/stop warning light comes on

Hi all,

I'm new to this forum and I have a question about a rather annoying problem that has developed in my 500.

It's a 2011 500 Lounge, 1.2 petrol, with 56,000 miles on the clock. I bought it second-hand from a private seller in April 2016 (at 52,000 miles). It's had one previous owner, who got all the servicing done at a Fiat dealer.

It's developed an intermittent fault of spluttering/juddering (not sure on the right word here) on acceleration. It's usually when the engine is cold after just starting up (it's just done it very violently tonight in -1C weather). I'll be accelerating, usually on about 2000-2500rpm (it will do it in any gear at any speed) and then it will just start juddering and decelerating quite sharply. It's a difficult one to explain but it's very sharp and causes the car to lose a lot of speed instantly. Luckily, I haven't had anyone too close behind me when it's happened.

But here's what really confuses me about it. Everytime it does this, the Start/Stop disconnected warning light comes on and stays on until the engine is turned off.

I took it to an independent dealer in September and told them about this, but they just took this as meaning it was a problem with the start/stop system. I don't think it is. I'm pretty sure it's to do with the fuel intake, but I'm not certain.

I'm wondering if anyone else has had a similar issue? How do I fix this? It's quite disconcerting when it happens and it needs fixing.

Thanks,
Jake

Hello and welcome .

Sorry to hear you're having problems.

The 1.2 engine is known for occasional rough running when cold; there's not generally a single cause, but changing the spark plugs, preferably for something better than the OEM parts, often helps. The problem is often exacerbated if the car is started when cold, then stopped and subsequently restarted before it's properly warmed up.

Reading any stored error messages with a fiat-specific code reader such as multiecuscan may shed further light on the matter. Generic code readers aren't usually much help in cases like this.

I'd agree the S/S may be a red herring; just about any fault with the car will trigger the S/S unavailable message.

A couple of times I've nearly stalled and had the S/S unavailable message, so I'd be inclined to agree with any advice to ignore it.

... but don't ignore the spluttering/rough running; continuing to use the car in that condition isn't good for it.

My suggestion, take it to Fiat and pay your £60 see what they say, there's too many things it could be, fuel or spark would be my first guess but poor info to the ECU could cause this, given its intermittent nature it may not be a simple "oh, that's whats wrong" ?
When it starts spluttering(misfiring I suspect) are there any other lights come on, like the engine light even if only for a short time, also if you keep driving does the issue disappear or remain until say switched off then on again? If the engine light comes on does it stay constant or flash(if safe to do so how many times)
Also sounds similar to this post; https://www.fiatforum.com/500/445493...ew-months.html

Thanks for the replies.

I've had a look at changing the spark plugs this morning but found they're so far hidden it's going to be very difficult to work on them. I also found the bracket for the air intake hose, connecting it to the body at the front of the engine bay, had snapped off, so the air hose was just hanging there. I've fixed this now - not sure if it had any effect on the performance.

I later went out for a quick test drive and it ended up driving a lot worse than before. I was driving through the centre of town, doing about 30mph in third, at about 2200 revs, and it just jumped and studdered, as if it was going to stall, and the revs just dropped instantly to 1300 then picked back up again. It did this about ten times in five minutes.

I've just taken it to a Fiat garage. I'm sure it's going to cost quite a bit but it's getting very difficult to drive so I've not really got much choice.

The spark plugs are not that hard to do once you've moved the air box out of way, a bit awkward but quite doable, the brass fitting can come away from the air intake at the front a bit super glue and all good.
Remember once diagnosed you don't have to let them do the work?

Check spark plugs/clean map sensor/check coil- in that order!

cars been to a workshop.. lets wait to see what they did for @swifty500

Can't wait to see just how wrong i was!!