Technical 16v 1.2, uneven on low rpm and error u1702

[Ancan]

Greetings!
I'm stumped with a problem on my mk2b, and I hope someone will be able to point me to the right direction.

The car has been running without problems since I bought it three months ago. Today I finally got to replacing the rear shocks and fitting one of those plastic engine covers underneath. After this, the wife took the car but didn't get more than four kilometers before it started running bad, and I had to go get both her and the car back.

It runs OK at idle, but when you apply throttle it misfires half a second or so, until the RPM goes up. It's driveable but accelerating makes it misfire.

The OBD lists two errors:
Current Fault: U1702 - CAN network (NCM-NBC)
Pending Fault: U1700 - CAN network (NCM-NGE)

It seems that "the dreaded D4 connector" is often mentioned when U1702 comes up, so I located and checked the connector. It looked dry, with no corrosion, but I sprayed some electronics-cleaner on it anyway, and also fixed the other connectors while I had the fuse-box open. I also checked the two big black/blue connectors on top of the throttle-housing, and gave them some spray as well.
It didn't help.

I have also noticed that when the ignition is on, but the engine is not running, there's a twitchy, buzzing sound from the throttle housing. This might be normal, since I have not been paying much attention to sounds from the throttle housing before.

My plan tomorrow is to check out other connectors in the engine compartment.

If anyone have any idea what could be the problem, please help.
Thanks

P.S.
(I *knew* I shouldn't have bought those cheap polish shock-absorbers. It's probably them that are incompatible with the ECU).

 

[Ziggy122]

Greetings!
I'm stumped with a problem on my mk2b, and I hope someone will be able to point me to the right direction.

The car has been running without problems since I bought it three months ago. Today I finally got to replacing the rear shocks and fitting one of those plastic engine covers underneath. After this, the wife took the car but didn't get more than four kilometers before it started running bad, and I had to go get both her and the car back.

It runs OK at idle, but when you apply throttle it misfires half a second or so, until the RPM goes up. It's driveable but accelerating makes it misfire.

The OBD lists two errors:
Current Fault: U1702 - CAN network (NCM-NBC)
Pending Fault: U1700 - CAN network (NCM-NGE)

It seems that "the dreaded D4 connector" is often mentioned when U1702 comes up, so I located and checked the connector. It looked dry, with no corrosion, but I sprayed some electronics-cleaner on it anyway, and also fixed the other connectors while I had the fuse-box open. I also checked the two big black/blue connectors on top of the throttle-housing, and gave them some spray as well.
It didn't help.

I have also noticed that when the ignition is on, but the engine is not running, there's a twitchy, buzzing sound from the throttle housing. This might be normal, since I have not been paying much attention to sounds from the throttle housing before.

My plan tomorrow is to check out other connectors in the engine compartment.

If anyone have any idea what could be the problem, please help.
Thanks

P.S.
(I *knew* I shouldn't have bought those cheap polish shock-absorbers. It's probably them that are incompatible with the ECU).

please tell me your kidding?

Anyway - U codes are pending codes - ie developing but not a fault yet
I recommend you clear the codes - run the car and re-read the ECU

If the car is misfiring - Have you checked all Plugs - leads and coils?

Ziggy

 

[Ancan]

Yes, I was kidding

I'll check the ignition today.

 

[Ancan]

I couldn't find a socket narrow enough to fit the holes for the spark plugs, so I didn't get that far. However, I have read that you might need to modify the OBD2-reader for FIAT/Alfa Romeo's, and perhaps also use a special software for these cars (like MultiECUScan).

Could it be that I'm being mislead regarding the codes?

 

[Ziggy122]

my bad i assumed you had used FES / MES (fiat/Multi Ecu Scan)

Get the free edition it will read the engine side with ease
The standard KKL/Vagcom or Elm 247 i think it is are fine too

I know the 8v uses 16mm spark plug socket - but dont know about 16v

Ziggy

 

[Ancan]

my bad i assumed you had used FES / MES (fiat/Multi Ecu Scan)

Get the free edition it will read the engine side with ease
The standard KKL/Vagcom or Elm 247 i think it is are fine too

I know the 8v uses spark plug socket - but dont know about 16v

Ziggy

Most of my computers are on Linux, so MultiEcuScan was a bit troublesome, but after I borrowed my wife's computer I got it to run. Unfortunately, it says that the module I need is not available on the free version (Bosch Motronic ME7.3H4 EOBD Injection), and I'm too cheap to buy a registered version just now. The car is kind of driveable, so I might take it to a shop and let them read it instead.

The issue with the spark plugs are that they are located in deep wells, and the holes are so narrow that my "standard" plug sockets won't fit. I'd either have to narrow my socket down with a grinder, or get a new one that fits. I'll have to get to that tomorrow.

I got this reply in another thread: "I think the codes are for canbus errors. I'd check the state of the battery, alternator and earths, but then do the old start it up in the dark, look for blue flashes under the bonnet thing (temporarily removing the air filter gubbins will help visibility). "
U1702 might be something with the cambus between the ECU and power steering. Power steering works fine (city mode also), so I don't know if its a false lead.
I have grounded the egine properly with jump-start-cables, but it doesn't help. The battery is new, and I have good voltage from the alternator. No sparks in the engine compartment. It's completely pitch black here in Swedish countryside now, so they would have been seen clearly.

I'm starting to wonder if it could be a sticking valve, but don't know if the symptoms match. The engine runs mostly fine when not under strain, with just a small hickup now and then when idling.

Damn it. This was meant to be a troublefree car.

 

[Ancan]

I managed to get the error codes via MultiECUScan by choosing the 1.4L 16V engine instead, and they are the same so I guess the are valid.

Right now:
U1702 - No signal, Fatal
U1700 - No signal, Fatal, Light ON
U1601 - Invalid signal, Stored, Light ON
U1600 - Invalid signal, Fatal

U1600, U1601 is probably because I've been messing with the contacts (D4 and the two on the ECU).

 

[Ziggy122]

U1600 - thats immboliser not picking up the key
I think u1601 is too

but the U1700 / U1701 is odd....
Seems to be a CANBUS error - ie something is communicating properly

Ziggy

 

[Ancan]

I'm more and more convinced the error codes are a false lead. They might be proper errors, but not related to the issues I have.

I've had a couple of more days to get a feeling of the symptoms.
Engine is a bit unsettled at idle. While driving it seems OK, until you apply too much gas when it hesitates and start stuttering. If you keep forcing it, the engine warning light will start blinking for a moment. Fuel economy seems unaffected.

Error codes U1700, U1701 is about cambus network errors. Migth be oxidated contacts, bad grounding or something like that.
U1600 and U1601 is about the key code, which seems odd because it starts fine and doesn't show any warning lights for this.

What I've done:
Cleaned all contacts in fuse box and on ECU.
Cleaned throttle body.
Verified engine grounding with jump cable.
New plugs
New leads

Next:
New coil

If it's not the coil, I'm running out of ideas. Sticking valve perhaps.

 

[s and b]

i wonder if your throttle /accelerator pedal potentiometer is worn?
you dont give mileage or whether owner plays tunes on it with engine off

did you try using linux and wine to get fes to work?
it might do for future

 

[Ancan]

i wonder if your throttle /accelerator pedal potentiometer is worn?
you dont give mileage or whether owner plays tunes on it with engine off

did you try using linux and wine to get fes to work?
it might do for future

I lack the language skills to really decypher this (English is not my native language), but is it about sound coming from the throttle body? I mentioned it in the first post:

"I have also noticed that when the ignition is on, but the engine is not running, there's a twitchy, buzzing sound from the throttle housing. This might be normal, since I have not been paying much attention to sounds from the throttle housing before."

Also, I woke up today thinking about clogged injectors. I might put a bottle of injector cleaner in the tank before I try the coil pack.

 

[s and b]

I lack the language skills to really decypher this (English is not my native language), but is it about sound coming from the throttle body? I mentioned it in the first post:

"I have also noticed that when the ignition is on, but the engine is not running, there's a twitchy, buzzing sound from the throttle housing. This might be normal, since I have not been paying much attention to sounds from the throttle housing before." they do seem to make this noise so can be ignored

Also, I woke up today thinking about clogged injectors. I might put a bottle of injector cleaner in the tank before I try the coil pack.

i was thinking throttle pedal is worn out in its internal tracks
can you borrow one to try an alternative one?

 

[Ancan]

Fixed today. It was the coil pack all the time, which I probably would have figured out much earlier if I hadn't put any weight to the OBD readings. OK, the OBD helped me see which cylinder was having issues, and that it moved when I swapped leads between cylinder 4 and 1. If the fault would have been before the coil, both ought to have misfired due to wasted spark and shared coil. After the coil, everything was already replaced.

Thanks for the help!