Hi everyone,

My Fiat 500 presents some strange behavior. It acts like it's choking when the radiator fan is on.

I noticed the exhaust vibrates once every few seconds. I didn't notice a significant drop in RPM. It sounds like pressure is building up on the exhaust end.

I made this video here to describe the issue:


When cooling is not required by the fan, it behaves fine. AC compressor was off for the entire test period.

Not sure if this can be caused by a split exhaust manifold, which I'm primarily suspecting for a tappety noise which I detailed in this separate thread.

Is there anything I can check myself before visiting a garage? I cannot understand how engaging the radiator fan causes this.

Thanks in advance!

Remix1989 said:

Hi everyone,

My Fiat 500 presents some strange behavior. It acts like it's choking when the radiator fan is on.

I noticed the exhaust vibrates once every few seconds. I didn't notice a significant drop in RPM. It sounds like pressure is building up on the exhaust end.

I made this video here to describe the issue: https://youtu.be/kI717lVDFHU

When cooling is not required by the fan, it behaves fine. AC compressor was off for the entire test period.

Not sure if this can be caused by a split exhaust manifold, which I'm primarily suspecting for a tappety noise which I detailed in this separate thread.

Is there anything I can check myself before visiting a garage? I cannot understand how engaging the radiator fan causes this.

Thanks in advance!

Click to expand...

If you do have a split or hole in exhaust manifold or manifold gasket it can cause the ecu to inject far too much petrol.

Thank you for the explanation, jackwhoo!
Didn't know air leak on the exhaust side could as well induce the ECU to inject more petrol.
Maybe these have different causes after all then.

Is there anything else that can produce the choking, and still be related to the radiator fan?

Thanks a lot!

Can this be caused by a loss of compression in the cylinders? I would expect it to be present no matter of the fan running or not, if so...

What happens at idle if you turn on the rear screen and headlights? I.e. creating a large electrical load, also leave the a.c. on always regardless.

I will check again with all these 3 turned on and come back with the result.

I believe headlights were on in my previous test.

Could it be something related to the alternator? I know it was changed for a new one not many years ago (still looks like new under the hood).

Thank you!

Seems that low beam alone can make the engine choke but just at stating point. If i then switch to full beam, it does it the choking again but consistently this time (i.e. repeats every few seconds).

Seems to be related to creating a large electrical load.

Sounds like the motor is definitely under load..

Is it a 1242cc Essence : petrol motor

There is a 'fairly 'simple way of disconnecting the alternator.. so you can briefly run the motor.. and discover if your 'fault' has gone

Let us know if you want to hear more..

It may be your 'issue' is just a normal feature..

Thanks for the advice, varesecrazy!

Could it also be a dying battery? It has been replaced less than 3 years ago, though I know they can become defective earlier than that sometimes.

If the battery is not helping with the power output, wouldn't the alternator need to work harder to maintain electric demand?

Lots of potential causes..

I would remove the flywheel pulley.. so the alternator drive belt is free

Then temount pulley.. run engine..

Is the noise gone ? ... is the noise different??

Remove pulley ..refit belt

All done

It is an hours work tops.. will rule out alternator..and give you a quieter run of engine to check other sounds

Thank you! The idea sounds good.

I hope the battery will handle the electric demand alone for the time or the test. ?

Choking seems to have gone away after recently replacing the battery and the earth strap (from gearbox to chassis) with new ones. Thanks!

Just today, I was on the side of the road with the engine running, AC heater and low beams on, after some good minutes, the engine started stuttering and I've shut it down. When I finished my phone call, I turned the ignition on again and the engine won't start ...

I grabbed a multimeter and measured the voltage of the battery under the hood at 12.44V. Earlier choking-like symptoms came back too, way before this, relatively soon after I thought I've fixed the problem through buying a new battery.

I'm gonna try to jumpstart the car, just to rule out the battery (starter motor seemed to be spinning well though). Will come back with update. If no progress, though I avoided it by any means, I may pay a visit to the local dealership.

Later edit: Before this happened today, engine had been running for around an hour, cold starting was fine when I left home.

12.44 volts open circuit (ie, not under any load) should give plenty of go to start the engine but, if the engine was run for any length of time before that reading was taken I'd be hoping to see maybe 12.8 or 12.9 volts if the alternator and battery are in good order. I see you say in your third paragraph that the starter motor seems to be spinning well? Do you mean the starter is spinning but not turning the engine over? If the battery is able to spin the starter motor reasonably enthusiastically, especially if it's turning the engine over as well, then there's unlikely to be a battery problem.

Normally if engine revs dip due to load (Air con or alternator etc) the Idle Air Control Valve will open up a little and restore tickover revs to normal or even slightly above. I haven't opened your video yet so I'm away to do that right now.

Just watched your video - weird isn't it? As you say it sounds like a release of pressure. I've never heard exactly this symptom before but I have heard a very similar noise, although it didn't come and go like yours, on a car where the back box silencer was disintegrating internally and the glass fibre packing was partially obstructing the tailpipe. Try shining a bright light up the pipe and see if you can observe anything unusual.

I can't think how a load being applied to the engine would make the exhaust sound like this and I know that when the IACV kicks in, although it increases revs and makes the engine "work" a little harder (against the aircon or whatever) all it does is deepen the exhaust tone - it doesn't make that "whoosh". My bet would be something very strange going on inside the exhaust system itself?

PS. I'm assuming the noise is loudest at the end of the tailpipe? you don't hear it at the front? Also, Many exhausts may have a very slight gas leak at where the joints are. You might learn something if you get under the car - don't just support it on the car's own jack - and check at one of the joints nearer the engine. Pass your hand over where the leak is - taking care not to burn yourself. A normal leak of this type will "putter" at your hand but if there's a blockage going on I'd expect it to blow more vigorously whilst the tailpipe is making the "whooshing" noise. Of course if your system is gas tight this won't work.

Good luck and don't be telling us the car fell on top of you will you?

Checked the earth strap to gear box ?

Measure the voltage with the car running, the battery wont make much difference when the car is running unless it's severly f**ked.

Thank you for checking on this!

Yes, the starter motor spins quite well. I had some friend come over check the car and using a flammable spray, we managed to get the engine spinning even if for one second only. The battery seems fine, so are the spark plugs, there seems to be something wrong with the gas reaching the engine...

I ended up using a platform to take it to the dealership. This was on Tuesday, as they are short of personnel due to this sanitary thing, they didn't call me so far to let me know their findings, hopefully they won't empty my pocket.

Will keep this thread updated on the actual root cause. Thanks again!

If there's no signal from the cranksensor, the fuelsystem won't supply fuel.

gr J

Good point! Thanks for the great idea.
This is similar to what some German Group has as G28 sensor and I replaced it on my other car. It was back then I first heard of this dependence. Sigh, I left the car at the dealership on Tuesday and I still didn't hear back ... I'm gonna call them tomorrow, see what's going on.

All the best.