Technical Combustion problem.

[ccavalles]

Good morning.
I am trying to solve the problem with my Seicento 1.1. The car had a faulty camshaft sensor wire. Sometimes it would stall and not run combustion properly. I have replaced the wire with a new one, but the car is still emitting smoke and soot. It starts on the first try, no problem with that. The injectors were cleaned. Curiously, it didn't pass the vehicle inspection this year because of emissions; I touched the wire and it passed without any problems. I removed the spark plugs and they were dirty with soot. I put them back clean, but it still emits black smoke. Any idea what it could be? I see all the wiring is fine, coils and wiring were also replaced with new ones not long ago. The catalytic converter is also relatively new, as are the sensors.
When running, sometimes it works correctly and other times it seems like it has no power. But it does not stall.

In the video, more black drops than usual can be seen. I have put some cleaner through the exhaust.

 

[Mike1alike]

have checked the Seicento with two diagnostic machines and the following comes up: code P0170. Any idea what the problem could be? Thank you.

The code indicates a fuel trim malfunction. ECU is failing to maintain the correct air-fuel mixture.
From the few possible causes, I'm tempted to say that was not just a coincidence and maybe it is not all good with that cable yet.

I have replaced the wire with a new one, but the car is still emitting smoke and soot. It starts on the first try, no problem with that. The injectors were cleaned. Curiously, it didn't pass the vehicle inspection this year because of emissions; I touched the wire and it passed without any problems.

Is the sensor ok there? Sounds like bad contact, it going ok when you touched the wire.

 

[bugsymike]

The code indicates a fuel trim malfunction. ECU is failing to maintain the correct air-fuel mixture.
From the few possible causes, I'm tempted to say that was not just a coincidence and maybe it is not all good with that cable yet.


Is the sensor ok there? Sounds like bad contact, it going ok when you touched the wire.

I had similar on a Fiat Doblo 1.9 JTD MAF sensor , previous owner had tried new sensor , but issue was caused by a faulty plug to the sensor.
That one ran very rich/black smoke.Edit

 

[ccavalles]

I had similar on a Fiat Doblo 1.9 JTD MAF sensor , previous owner had tried new sensor , but issue was caused by a faulty plug to the sensor.
That one ran very rich/black smoke.Edit

Thank you for replying. Some time ago the cable started to fail, even at the ITV it tested negative. I touched the cable lightly and it worked fine, it passed the ITV ok. A month ago, a friend who also has a Seicento came over and brought the injectors cleaned at a mechanical workshop and we installed them, the cable would move and it no longer worked well. It even stopped. You touched it and it would start. Until it probably broke and didn’t work anymore. Then I bought a new cable. The car starts on the first try, but it produces that black smoke, gives errors, and doesn’t run smoothly.

I already say that it doesn’t always go wrong. It seems like some connection, injector wiring. All with contact cleaner to rule out, tightened correctly.

 

[bugsymike]

Thank you for replying. Some time ago the cable started to fail, even at the ITV it tested negative. I touched the cable lightly and it worked fine, it passed the ITV ok. A month ago, a friend who also has a Seicento came over and brought the injectors cleaned at a mechanical workshop and we installed them, the cable would move and it no longer worked well. It even stopped. You touched it and it would start. Until it probably broke and didn’t work anymore. Then I bought a new cable. The car starts on the first try, but it produces that black smoke, gives errors, and doesn’t run smoothly.

I already say that it doesn’t always go wrong. It seems like some connection, injector wiring. All with contact cleaner to rule out, tightened correctly.

Just a thought , was your diagnostic tool able to delete the error codes so cleared fully or are they coming back straight away.
Another possible thing that usually is only if a small bad running is , by disconnecting the battery and then on reconnection going for a drive so the vehicle "relearns" it normal running settings.

 

[ccavalles]

Just a thought , was your diagnostic tool able to delete the error codes so cleared fully or are they coming back straight away.
Another possible thing that usually is only if a small bad running is , by disconnecting the battery and then on reconnection going for a drive so the vehicle "relearns" it normal running settings.

Yesterday I connected the machine, cleared the fault. I reconnected the machine and an error appeared. Disconnected the battery. Today connected and same fault. Anyway, that little bit of black smoke is not normal.

 

[ccavalles]

let's see if you notice anything strange.
photos from before changing crankshaft cable and sensor

 

[ccavalles]

I had similar on a Fiat Doblo 1.9 JTD MAF sensor , previous owner had tried new sensor , but issue was caused by a faulty plug to the sensor.
That one ran very rich/black smoke.Edi

It could be the cause. If I don't find a fault, I will ask a friend for a complete set of cables from another Seicento to test.
It seems that the Fiat wiring is not very good quality.

 

[bugsymike]

Do you mean apart from the wiring loom repair, the very tight wire to the plug and the spare plug beside it in the last photo and the pretty green/blue odd loose non automotive wire in second photo? Bear in mind my eyes are 73 years old so may still be missing things.
That and the first photo of engine compartment looks cleaner than the rest, or is it the last photos are zooming in on the dirt.

 

[ccavalles]

Do you mean apart from the wiring loom repair, the very tight wire to the plug and the spare plug beside it in the last photo and the pretty green/blue odd loose non automotive wire in second photo? Bear in mind my eyes are 73 years old so may still be missing things.
That and the first photo of engine compartment looks cleaner than the rest, or is it the last photos are zooming in on the dirt.

The green cable is a wire that I used to hold up pipes. These are photos that I keep when I do things to the car. In that case, it was the heater radiator. The photo is misleading, everything is actually quite clean.

 

[bugsymike]

The green cable is a wire that I used to hold up pipes. These are photos that I keep when I do things to the car. In that case, it was the heater radiator. The photo is misleading, everything is actually quite clean.

Not intending to cast doubt on the cleanliness and much cleaner than most of my vehicles.
Apart from what I assumed to be an air con aluminium fitting I didn't notice the heater hose disconnected.
My vehicles often look clean just after purchase as I use my commercial steam cleaner to excess around the engine and everywhere else, indeed I once blew away a imobiliser chip that had been repositioned with the key antenae behind the dash board on a very dirty Iveco Daily pick up ex Water Board from auction. I cover ECU with a plastic bag and go for it, so far with no problems. I keep the engine running for sometime with the bonnet up so that and the hot steam soon dries things.

 

[Mike1alike]

You could try a reset of the learned parameters. You certainly can do that with MES, I don’t know if you can do it with the tester you have.
But if there is a physical problem like faulty cable, that needs to be sorted out first in order to fix it. The cable you moved and it made it work... watch around it, the other end or maybe it pulled something else when you moved it...

 

[ccavalles]

You could try a reset of the learned parameters. You certainly can do that with MES, I don’t know if you can do it with the tester you have.
But if there is a physical problem like faulty cable, that needs to be sorted out first in order to fix it. The cable you moved and it made it work... watch around it, the other end or maybe it pulled something else when you moved it...

That's what I'm looking at, connections, touching cables to see if it returns to normal and detect which one it is. But for now, there is no luck. It could be the upper sensor wiring.

 

[ccavalles]

here is a video of the car when it arrived home. Inheritance from a deceased relative. The car had 27,000 km. It was in 2011. Instead of it being scrapped, I kept it.

current condition, small details, sporting wheels, original tachometer, black strip on door frame.

 

[Pugglt Auld Jock]

here is a video of the car when it arrived home. Inheritance from a deceased relative. The car had 27,000 km. It was in 2011. Instead of it being scrapped, I kept it.


View attachment 488694
current condition, small details, sporting wheels, original tachometer, black strip on door frame.

Too right, I'd have been keeping it if it were me too.

 

[ccavalles]

This morning I took out the connection to see what I would find. The wires were bare. I separated them and tried the machine. And it didn’t give an error anymore. I turned it off, disconnected the battery, started it up again, and connected the diagnostic. Nothing, 0 faults. Then I started taping it up and making it right. Still need to test on the road, but it seems the problem is solved. The heat and time have destroyed the insulation. I don't know if wiring harnesses are still available new. If they are, I would put them in.

 

[Pugglt Auld Jock]

View attachment 488720

View attachment 488722
This morning I took out the connection to see what I would find. The wires were bare. I separated them and tried the machine. And it didn’t give an error anymore. I turned it off, disconnected the battery, started it up again, and connected the diagnostic. Nothing, 0 faults. Then I started taping it up and making it right. Still need to test on the road, but it seems the problem is solved. The heat and time have destroyed the insulation. I don't know if wiring harnesses are still available new. If they are, I would put them in.

This is an absolutely classic example of why you can't litteraly take a fault code deffinition as "gospel truth". The inexperienced person, looking at a fault code, will see reference to, perhaps, an Oxygen sensor, MAP/MAF sensor, Crankshaft sensor, or any number of others and immediately go out and buy said sensor. The problem is often that the signal is not getting through to the ECU due to a high resistance in a connector or damage to wiring, - as we see here. Perhaps even just a MAP/MAF sensor needing a good clean? Thorough checking visually and for continuity before "firing the parts cannon" is where investigations should nearly always start. The satisfaction when you find something relatively simple, like this, is enormous.

Edit. There's also a subtle problem with indescriminately "firing the parts cannon". Whilst unplugging the old one, very possibly moving the connector and loom around a bit and then plugging into the new one will sometimes cause a "cleaning effect" on the plug connector parts or realignment of the wires in the loom so, when they might have been making contact due to damaged insulation the movement moves the wires to a new position where they are not touching. It's quite possible that the improvement in connection in the connector plug or movement of the wires will temporarily restore normal running so you think the problem is solved, only to find it returns at a later date as the original problem reestablishes itself. I like to use a connector grease whenever I have a connector apart and find I very seldom get problems with connectors I've treated in this way. The stuff I'm using just now is Contralube 770 - which I think is no longer made. It's very similar to a dielectric grease but claimed to contain "stuff" which was particulary good at giving long term protection against corrosion. The tube I have is still half full so likely to last me out.

 

[ccavalles]

This is an absolutely classic example of why you can't litteraly take a fault code deffinition as "gospel truth". The inexperienced person, looking at a fault code, will see reference to, perhaps, an Oxygen sensor, MAP/MAF sensor, Crankshaft sensor, or any number of others and immediately go out and buy said sensor. The problem is often that the signal is not getting through to the ECU due to a high resistance in a connector or damage to wiring, - as we see here. Perhaps even just a MAP/MAF sensor needing a good clean? Thorough checking visually and for continuity before "firing the parts cannon" is where investigations should nearly always start. The satisfaction when you find something relatively simple, like this, is enormous.

Absolutely right. In another car I have, a Citroën CX, it wouldn't start. Without getting nervous, I started checking and found nothing unusual. A neighbor, who turned out to be a computer technician, came over and looking at it told me that the sensor connections were green, and he said, 'buy some contact cleaner and try.' Sure enough, that was it. It hasn't had any more problems.