Hi guys!

At my wits end with my 1.2 69bhp 63 plate 500S. I'll try to make a long story short.. it has an intermittent misfire. Also, when driving it at high speeds (70mph+), sometimes the engine management light will come on and the car starts chugging as if I'm running out of petrol. When the engine is switched off and back on, the EM light goes off and car runs as normal once again (still with the intermittent misfire but minus the chugging). When plugged into the diagnostic, the fault code reads as misfire cylinder 3 along with a few others. However, everything that the codes refer to I've had replaced. Replaced coil, spark plugs, lambada sensor etc etc with genuine parts.. it's also recently had a software re-flash for a problem with it being underpowered.

Does anyone have any experience of this? Helpppp!

Ecu?

Thanks for replying typecastboy .. I'll ask my mechanic to check it out!

Have you replaced the spark plug leads? Ours suffered no.4 failure, you could see and hear the spark jumping across .

sarahlouiseslj said:

Thanks for replying typecastboy .. I'll ask my mechanic to check it out!

Click to expand...

Hi,
does this mean it's outside of the FIAT dealer network..??
far from an issue here .. BUT you may not be using the best diagnostic equipment for the 500.

some error codes generated are so general it can cover many components..
sound familiar..
Fiat / Alfa specific software should be more accurate


Charlie - Oxford

In my experience with the euro 6 engined 500 the ecu's are a bit prone to intermittent faults. I had one with a very intermittent missfire. Ruled out all the obvious so fitted the ecu to one of our courtesy cars and after quite a few miles of road testing the fault appeared on the courtesy car. Fitted a new ecu and all was good after that. If it's that be prepared for a very expensive repair. Where are you in the country?

John202020 said:

Have you replaced the spark plug leads? Ours suffered no.4 failure, you could see and hear the spark jumping across .

Click to expand...

Yes these have all been replaced thanks for your reply though!

varesecrazy said:

Hi,
does this mean it's outside of the FIAT dealer network..??
far from an issue here .. BUT you may not be using the best diagnostic equipment for the 500.

some error codes generated are so general it can cover many components..
sound familiar..
Fiat / Alfa specific software should be more accurate


Charlie - Oxford

Click to expand...

Hey, thanks for your reply. Yes it's been to Fiat, and my mechanic also has the Fiat software.. nobody seems to be able to come up with any solutions! I seem to be reading a lot about misfiring issues with 500's :/

burrowsdeano said:

In my experience with the euro 6 engined 500 the ecu's are a bit prone to intermittent faults. I had one with a very intermittent missfire. Ruled out all the obvious so fitted the ecu to one of our courtesy cars and after quite a few miles of road testing the fault appeared on the courtesy car. Fitted a new ecu and all was good after that. If it's that be prepared for a very expensive repair. Where are you in the country?

Click to expand...

Hello, thanks for your reply .. I'll definitely look into this! It's driving me mad. I'm around half an hour from Cardiff, more Newport way.

varesecrazy said:

Hi,
does this mean it's outside of the FIAT dealer network..??
far from an issue here .. BUT you may not be using the best diagnostic equipment for the 500.

some error codes generated are so general it can cover many components..
sound familiar..
Fiat / Alfa specific software should be more accurate


Charlie - Oxford

Click to expand...

Absolutely. MultiECUScan gave me an error which led me to change the throttle pedal and the throttle body. The fault codes were cleared and they just came straight back again. Took it to my trusted independent and although they worked on it on and off for nearly 4 weeks, their software traced it to a voltage problem within the ECU. One volt higher than it should be which triggered the fault. MultiECUScan would never pick that up. I had to get a new ECU but it had to go to the garage for that.

It's odd that it misfires at high revs normally it would be at idle and low speed and pulling away does the EML light flash when it comes on then steady ? Of course a misfire is not just the spark, could also be injectors and valves.

John202020 said:

It's odd that it misfires at high revs normally it would be at idle and low speed and pulling away does the EML light flash when it comes on then steady ? Of course a misfire is not just the spark, could also be injectors and valves.

Click to expand...

The misfire has happened at both low and high revs, but seems more prominent at higher revs/speeds. The EML has only ever come on when going 70mph and flashes, never stays on steady. EML light then disappears when engine is turned off and back on again. Injectors have been taken out, tested, cleaned, replaced etc etc.. I can't keep up with the amount of things we've tried and tested to be honest! I've also tried fuel treatment and a gas treatment.. My brain hurts!

Wow you've certainly replaced and checked a lot, some parts like the Lambda were probably fine, next would suggest hooking up to a laptop/data logger whilst driving to see just what the ECU is doing? sounds too obvious but the connections to the ECU are good, and clean? Do you get 3 flashes then pause?
Do you know what the other codes were by chance?
Not sure but a secondhand ecu may be the way to go, only when its confirmed faulty.

I bought a secondhand ECU and it has to be virginised before it would work but sorted out my problem.

burrowsdeano said:

In my experience with the euro 6 engined 500 the ecu's are a bit prone to intermittent faults. I had one with a very intermittent missfire. Ruled out all the obvious so fitted the ecu to one of our courtesy cars and after quite a few miles of road testing the fault appeared on the courtesy car. Fitted a new ecu and all was good after that. If it's that be prepared for a very expensive repair. Where are you in the country?

Click to expand...

sounds promising ,

big question here is wether sarahlouiseslj has still enough warranty left for a Fix through FIAT dealership network..,

Charlie

If you send me your reg number I can check to see if you have any warranty left and if it's covered

John202020 said:

Wow you've certainly replaced and checked a lot, some parts like the Lambda were probably fine, next would suggest hooking up to a laptop/data logger whilst driving to see just what the ECU is doing? sounds too obvious but the connections to the ECU are good, and clean? Do you get 3 flashes then pause?
Do you know what the other codes were by chance?
Not sure but a secondhand ecu may be the way to go, only when its confirmed faulty.

Click to expand...

Tell me about it ... I'll pass this onto my mechanic and see what he thinks, definitely worth investigating though. Not sure on the flashes? I think it just continues to flash as far as I'm aware but I'll check the next time it comes on. My mechanic took a photo of the codes the last time the EML came on so I'll get hold of that too. Thanks for the input though, it's much appreciated!

typecastboy said:

I bought a secondhand ECU and it has to be virginised before it would work but sorted out my problem.

Click to expand...

Thanks for sharing your experience, much appreciated. I'll pass it on to my mechanic

varesecrazy said:

sounds promising ,

big question here is wether @sarahlouiseslj has still enough warranty left for a Fix through FIAT dealership network..,

Charlie

Click to expand...

I don't.. it's just out of warranty. To be honest though, I just want it sorted either way!

burrowsdeano said:

If you send me your reg number I can check to see if you have any warranty left and if it's covered

Click to expand...

Thank you so much for this, I really appreciate it. However, I've already been in contact with Fiat and it's no longer in warranty. It ran out a few weeks ago. Thank you all the same!