Hi there,

I've recently picked up a 2013 Fiat 500 Twin Air (0.9) on which I'm ironing out the bugs as I'm finding them. One odd one which I've noticed is that cruising in 4th gear around 60 to 65 mph, I'm getting a fairly subtle pulsing vibration in around 1 second intervals (not wheel balance). The vibration is almost like what you'd get if you were in too low gear, but pulsing.

This pulsing vibration doesn't happen in other gears at the same speed ie. 60mph in 3rd is fine.

Once I go over roughly 65mph, the pulsing vibration/resonance goes away but returns immediatey when slowing back down.

Coil packs, airfilter and plugs are new, tyres are good (in theory). Rear shocks are documented as being replaced a couple of years ago.

I do get a deep rumble from the front brakes when I'm reversing (which might suggest sticking pads) but as the issue seems to only appear in 4th gear, I'm not sure that's going to be it.

Would any of you fine people on here have any ideas what to explore? Is there such a thing as an ECU update or anything that I should look out for etc ?

Oh, and no fault codes...

Thanks in advance.

Hi

Is this a constant?

Can you replicate it 'at will..'

Hot or cold..wet or dry ??

My 2013 is developing similar..

But only after a LONG drive.. Im starting by tracing a misfire.. but your issue sounds like a mechanical vibration..

how many miles on yours?

Hi varesecrazy - Yes, my 'vibration' is constant and can be reproduced 'at will', which makes a change actually. (Most of my faults seem electrical and intermittent)

I'm quite high milage for the age at 93K and the problem seems to be regardless of temperature although the car has warmed up by the time I get to anywhere that I can drive 60 but will try it on the way home from work today.

Wet or dry doesn't make a difference.

...by the way, if you start tracking your misfire by replacing the coil packs, carefully watch those pesky connectors which are very counter-intuitive to dis-engage. Push the black tab down and pull. I levered the black tab up and ended up snapping the little yellow locking part ! ...also, it might be obvious, but a skinny, long, captive plug socket is essential (I'm used to plugs which are less 'buried' in the engine). If you're getting a proper misfire, one of those relatively cheap code readers on Amazon might give you a head start. Search on Amazon for this (Foseal Wired Car OBD2 Scanner, Plug and Play Code Reader, Wired Car OBD2 Scanner, HD LCD Display Screen, Red)

Is it a specific Rengine revs related, ie 60mph in 4th, 45mph in 3rd etc ?

Any worse when cornering one way or the other, wheel bearing ?

Hi percymon, no, it doesn't appear to do it at the same RPM in different gears other than 4th. It's possible that the issue is there at the same RPM in different gears but as there's less load, the effect might be masked. Steering one way or the other doesn't seem to make any difference. you only really notice it when cruising steadily on straights. I'll have to try swerving about a bit on the A12 when no one is looking to see if there's an impact

Its worth swapping your wheels front to back.. cheap diagnostics

Its worth swapping your wheels front to back.. cheap diagnostics

Click to expand...

Good idea, I'll try that

Yes good advice swapping wheels.. My twinair had wheel balance type issue when I bought and went to two tyre shops searching the cure - First crowd took money for a balance with no cure, but I took the second guy to task after he balanced with no improvement so he inspected each tyre and did three road tests and finally found that one was slightly oval in shape (by spinning on the car with a fixed point against the tyrewall line) - replacing required but the manufacturer supplied a new tyre. The previous owner had done 10,000 kms with the faulty tyre..

JCU said:

Hi varesecrazy - Yes, my 'vibration' is constant and can be reproduced 'at will', which makes a change actually.

...by the way, if you start tracking your misfire by replacing the coil packs, carefully watch those pesky connectors which are very counter-intuitive to dis-engage. Push the black tab down and pull. I levered the black tab up and ended up snapping the little yellow locking part ! ...also, it might be obvious, but a skinny, long, captive plug socket is essential (I'm used to plugs which are less 'buried' in the engine)

Click to expand...

Thanks

I changed the one plug..and checked the airfilter element.. wary of generating a 'new fault' I didnt do too much

I made do with a traditional 'small' plug socket ( 16mm Hex?)
And a telescopic magnet tool.. you can sometimes wind the plug in a couple of turns on the magnet..

But being in such a deep well its 95% guaranteed to be 'square' on the thread

I will post the pics and info into a GUIDE or 3.. very little twinair info on here

Well in the end I tracked down a tyre centre with facilities to test the wheel 'roundness' specifically. I did get an odd look when I gave them fairly precise instructions on what to look for and discovered that one of the rear wheels was out of shape (the last one they tested) - So now the bidding starts on a new set of wheels ! I was going to have the old ones re-furbished at some point anyway and would have been fairly narked off if I'd had an egg-shaped wheel be re-done ! - Thanks everyone for pointing me in the right direction. I'm almost relieved to have found a definitive solution to a problem for a change !

Chopin said:

finally found that one was slightly oval in shape (by spinning on the car with a fixed point against the tyrewall line) - replacing required but the manufacturer supplied a new tyre.

Click to expand...

I had something similar on two consecutive new Fords in the 1970's; all four tyres replaced due to being 'out of round' at around 10,000 miles in each case. Both times, the tyre manufacturer gave the tyre centre 100% allowance for the cost of the tyres, but I had to pay for fitting and balancing.

Interestingly the main dealer who sold the cars didn't want to know; they just said tyres weren't covered by the new car warranty and wouldn't help at all. The local tyre centre was much more helpful and sorted it in minutes with a phone call to the tyre manufacturer.