Technical Fiat Panda 1.1 stalling while driving going over humps when cold

[andreizabest]

I have a 2006 Fiat Panda 1.1 and the engine just stalls while driving. If a gear is engaged the car will jolt and the engine continues running, the engine management light briefly comes on but goes away just as quickly, but if a gear isn't engaged or I have the clutch pressed the engine stalls. It seems to happen more often when the engine is cold. The issue seems to occur fairly consistently if the engine is cold and I'm driving over speed bumps, right as I go over them the problem occurs but if the engine is warm it seemingly rarely happens. It also occurs when coming to a stop at the lights. The engine sounds and runs completely fine outside of this, it idles fine as well with no issues. To me it kinda seems like an electrical problem maybe, given going over bumps when cold gets this to trigger fairly consistently. Maybe some bad connection somewhere, and as the engine warms up it makes a better connection.

I've taken it to a mechanic and they told me that the engine sounds and runs really great and said that they can't do much if there's no code and they'd start by replacing spark plugs, ignition coils etc and that I should probably get a second opinion. I have an appointment with a more specialised mechanic that also deals with potential electronic issues so they can properly diagnose it but I wanted to know if anyone here had any ideas or what I should expect.

 

[koalar]

It's likely to be

The wiring loom to the ECU, which often cause the engine to cut out going over speed humps, usually there is either a coil or injector error code

The battery earth strap, which has been known to cut the engine with no error

Lastly the crank sensor, never know this to fail over bumps, but it often temperature related and also often gives no codes

As will a loose battery terminal


Need to try and narrow it down

With the engine running

Grab the earth strap under the battery tray and wiggle the cable

Does the idle change

Try tapping the panel under the keys

Gently wiggle the wiring loom to the ECU does the idle change, don't go mad here we are talking about moving the loom about gently, not pulling it that hard it breaks wires or connectors

People have managed to fix this in the past by cable tying the ECU connector down, save fixing or replacing the loom, you could try this first and see if the symptoms stop

Join a couple of cable ties together if they are too short

Try watching the dials as it happens, does the oil, immobiliser, battery or any other lights come on, does the time start flashing, does the back light on the clock go out

Engine stopped, with the ignition on, the engine check light should be on, so on its own with no error codes sounds more like a power/crank sensor issue, but that just a guess

 

[andreizabest]

It's likely to be

The wiring loom to the ECU, which often cause the engine to cut out going over speed humps, usually there is either a coil or injector error code

The battery earth strap, which has been known to cut the engine with no error

Lastly the crank sensor, never know this to fail over bumps, but it often temperature related and also often gives no codes

As will a loose battery terminal


Need to try and narrow it down

With the engine running

Grab the earth strap under the battery tray and wiggle the cable

Does the idle change

Try tapping the panel under the keys

Gently wiggle the wiring loom to the ECU does the idle change, don't go mad here we are talking about moving the loom about gently, not pulling it that hard it breaks wires or connectors

People have managed to fix this in the past by cable tying the ECU connector down, save fixing or replacing the loom, you could try this first and see if the symptoms stop

Join a couple of cable ties together if they are too short
View attachment 461384

Try watching the dials as it happens, does the oil, immobiliser, battery or any other lights come on, does the time start flashing, does the back light on the clock go out

Engine stopped, with the ignition on, the engine check light should be on, so on its own with no error codes sounds more like a power/crank sensor issue, but that just a guess

Thanks for the information.
I don't know whether I should be happy or dissapointed but the issue just dissappeared on it's own as of today, driving around town over bumps absolutely nothing, not even when cold, even took it to the carwash and no issue afterwards. But I'll still include some useful information maybe it helps narrow it down. I'm still going to take it to the mechanic to have a look at it.

The electrics stay on when the problem occurs, radio, dials, lights everything, no flashing clock either. I poked a little at the ECU cable but nothing seemed to change. The car has been decetly kept and only has about 43k miles so I kinda doubt the ECU has shaken itself loose yet. If I don't have a gear engaged when the problem occurs the car stalls completely as I've said so the appropriate oil, battery and engine lights come on. For what it's worth before issue started to occur I fueled it up Shell VPower, typically it get E10 petrol. Still running on that same fuel now.

 

[andreizabest]

It's likely to be

The wiring loom to the ECU, which often cause the engine to cut out going over speed humps, usually there is either a coil or injector error code

The battery earth strap, which has been known to cut the engine with no error

Lastly the crank sensor, never know this to fail over bumps, but it often temperature related and also often gives no codes

As will a loose battery terminal


Need to try and narrow it down

With the engine running

Grab the earth strap under the battery tray and wiggle the cable

Does the idle change

Try tapping the panel under the keys

Gently wiggle the wiring loom to the ECU does the idle change, don't go mad here we are talking about moving the loom about gently, not pulling it that hard it breaks wires or connectors

People have managed to fix this in the past by cable tying the ECU connector down, save fixing or replacing the loom, you could try this first and see if the symptoms stop

Join a couple of cable ties together if they are too short
View attachment 461384

Try watching the dials as it happens, does the oil, immobiliser, battery or any other lights come on, does the time start flashing, does the back light on the clock go out

Engine stopped, with the ignition on, the engine check light should be on, so on its own with no error codes sounds more like a power/crank sensor issue, but that just a guess

It started doing it again after I refuelled it back with E10 petrol again. Not as often though. Looking into it, could this have anything to do with the self adapation functions of the engine? Seeing as the shell VPower is E5 while now it runs on E10. It might just be a red herring. But I can't seem to find any information on how the self adapatation function works exactly.

After taking it to the mechanic they were able to get some stored codes out of it but they were the kind that cleared on their own and they said there's not much they can do since none of the errors really lead them anywhere. I think there were around 5 errors stored, 2 of which were canbus related and a 3 others I can't remember.

 

[koalar]

It started doing it again after I refuelled it back with E10 petrol again. Not as often though. Looking into it, could this have anything to do with the self adapation functions of the engine? Seeing as the shell VPower is E5 while now it runs on E10. It might just be a red herring. But I can't seem to find any information on how the self adapatation function works exactly.

After taking it to the mechanic they were able to get some stored codes out of it but they were the kind that cleared on their own and they said there's not much they can do since none of the errors really lead them anywhere. I think there were around 5 errors stored, 2 of which were canbus related and a 3 others I can't remember.

If it's over bumps no nothing to do with adaptive settings

Should make any difference which petrol it's on

If you have a smart phone you can read the codes yourself for a few quid

Grab the air box and jiggle it a bit

Do the revs increase

Under the air box is a large black inlet manifold, if you try and move this do the revs increase