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Discussion Starter #41
So far I've found 2 earthing points. One on the inner wing, other one next to the coils on the valve cover. I cleaned and brushed both of them. Car is still running fine but my lambda sensors have a different opinion
936377
936378

Both errors came up in the same time so god knows if it even means anything. The voltage on the log is low again, I'll try to find the rest of the grounding points tomorow.
 

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It does mean something. It means the ecu doesn't like the reading. If that's all that you're left with and the car is running fine, then it might be ok.
As I said, the JTs is very fussy and will throw up error coded for the slightest fluctuation
Fruity might come and say the same and he is by far more knowledgeable than I!
If it continues to run fine, theres a remap option available for the Jts ecu. IRS not a power remap. It's an improvement in drivability and a relaxation in the error code parameters. I think its Stephan at squadra (I stand to be corrected) that does it and it involves taking the ecu out and sending to him. I almost got mine done....until the
Gta SW fell in my lap 馃槈
 

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There has been no information whatsoever to suggest how the cylinder 3 misfire fault was cleared up. Was all the oxidised wire cut out or is it just a case of the is no fault right now so hope it stays that way? I hope it was the former but understand there are possibly more pressing things right now.

The fault then appeared to be the upstream no.1 O2 sensor. It logged a fault code which was consistent with the voltage dropping out momentarily from the sensor. That suggested a bad terminal somewhere but the voltages do look rather high. There has been no information to suggest what distance the car has travelled with these sensors. (odometer total distance?) Unlike earlier planar sensors, the wideband sensors do not return a voltage oscillating above or below 0.45 volts- they use a voltage reading to control what is essentially a planar sensor. That means that old sensors could display a wildly incorrect voltage for 95% of the time it they are bad. I've not seen this, BTW but it is what I understand of the function of these sensors. That's why I changed my sensors at 103K. I think in my case it was the 40mph urban-outskirts crawl which caused a very low voltage (below 0.5 volts).

What is the full range of operating voltage of your sensors? Mine was something like 4.3 volts (full throttle and high engine speed) to 0.5 volts during over run (no throttle at fairly high engine speed). I think it would be good to work out if the sensors are working correctly.

This one is unfortunately that straightforward and I guess you are not prepared to spend 拢100 on new O2 sensors until you know for sure they are bad (understandable).

With regard to the low voltage displaced via the diagnostic port, I'd start to look at the voltage outputted by the relay for the engine ECU. Over time, relay contacts can degrade and reduce voltage but so too can the terminals that the relay connects into. Unfortunately, in our cars, Alfa Romeo decided to put these things in the engine bay and not in a sealed box. That is how voltage-critical circuits, monitored by the engine ECU, are very prone to age/condition related failures on loads of our cars these days. There are loads of these faults posted in the forum now.

Yes, the JTS does have very close operating tolerances programmed into the ECU. That is great if the engine is brand new, wiring is new and any use has been solely on open roads. Obviously that is not the case. Stefan at Squadra Tuning has remapped my JTS (I haven't been able to try it yet- thanks to the Covid 19 spectre) but the fault code triggering parameters have been relaxed a little. The JTS remap won't increase performance as much as on a TS but driveability will be much better. I have also had extra work carried out for future modifications. I always knew the JTS would be a challenging engine to make reliable and get right but I got one mainly for the challenge in doing so. That and to prove various people wrong who stated the JTS doesn't sound as nice as a TS. Normally they are right but it can if it is maintained well and slightly modified.
 

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Discussion Starter #44
So the symptoms are back. It seems that the only cure for this problem is a highway run on full throttle for a钮 least 20-40 km. Then the engine starts to behave. Next morning it's the same all over again. I'm running out of ideas here. Could it be that the battery discharges a bit over the night which gives the poor electronics a hard time until I take the car for a highway run to charge it again? If that's possible, it could also lead to the bad earthing as you said. The battery is brand new btw (only like 1 month old) and the problems occured way before the battery change.
 

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Discussion Starter #45
Also I can't monitor the lambda readings while driving since the obd keeps disconnecting everytime I try to drive somewhere. I dont think this has anything to do with my problem but sometimes when I shut the car off it still tries to stay Alive for 1-3 second. This happens rarely but I find it interesting since no spark or fuel should be given to the engine
 

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So the symptoms are back. It seems that the only cure for this problem is a highway run on full throttle for a钮 least 20-40 km. Then the engine starts to behave. Next morning it's the same all over again. I'm running out of ideas here.
As expected. Range of O2 sensor return voltage? Knowing that may help.
 

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Discussion Starter #47
I'll try to play with the obd settings so it won't keep disconnecting and if it helps, I'll try to measure it
 

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If your error is ignition failure then my thinking says it is related to lack of spark rather than injector. Try pulling the coil pack out for that cylinder and attach an old spark plug and then run the engine. This will tell you if you are getting a spark. It could still be related to your extra wire (did you follow it to the other end) Maybe there is a bad connection somewhere else in the ignition circuit for No 3. Alfas are no stranger to bad connections.
 

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I read back more thoroughly and realise some of my comments were unhelpful given the information already posted. Sorry to be unhelpful.

Obviously I see high voltage and occasional dropping out. The other thing is low recorded voltage. To try to avoid just trying new sensors, try cleaning/replacing the connections for the ECU relay. Maybe even a new relay may help boost the ECU voltage. Ensure the main fuses are clean also. It is possible it is low voltage causes the diagnostic data stream to drop out.

Unfortunately I do not know what the symptoms are of failing wideband O2 sensors. I am guessing high voltage may be a symptom. That's why I ask what mileage/total distance of the car is. Another thought I have is has the car been remapped? If it has, disabling the weak mixture at up to 1400rpm may result in higher sensor voltage but I may just be clutching at straws.
 

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Discussion Starter #51
There's no need to apologise. I'm truly amazed and very thankful that you even try so hard to help me almost as if the car was your own. I should apologise to you for consuming your time. The Alfa community is amazing. Here's new info that came up in diagnostic today during my highway run. It signals rich mixture on all the cylinders and I believe an untrustworthy signal from lambda sensor? I took screenshots of the info. The other faults are misfire and bad variator solenoid.
 

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ok, having a think about that. Does the engine completely run well after a good run?
When do you cancel the fault codes?
Does cancelling fault codes affect any aspect of how the engine runs?

Cancelling fault codes under the EOBD system should also zero the self learning parameters. It looks like you are using an EOBD system rather than manufacturer specific software (correct?).
 

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Discussion Starter #53
I remove the codes after checking them so the engine doesn't try to run in any suspended mode of some sort. The fault code removal doesn't seem to have any effect on the engine behaviour. The engine runs completely fine after a good run. Usually till next day. I haven't read about the parameters being zeroed when removing the fault codes. But that can be done through a special function in the software (AlfaOBD or Multiecuscan). I have tried that many times already.
 

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So I take it the engine runs fine after a run regardless whether the fault codes are present or deleted. As it is O2 sensor faults, how long until the codes come back after clearing?
 

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Discussion Starter #55
The rich mixture faults came up today for the first time, the O2 sensor faults are very random and not very common yet
 

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The P0300 and P0303 faults look very much like the bad wiring to the number 3 ignition coil. It looks like this has to be fixed properly before eradicating the other faults. I think the bad wiring should be cut out and new wiring spliced in ideally with non insulated butt connectors which are crimped in place and covered with heat shrink.

The other thing to do is follow my advice about the positive wiring to ECU via terminals, relay and main fuse in engine bay. That may correct the other faults but it needs to be methodically worked through.
 

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Ok, I get the bit about 'removing fault codes so it doesn't run in a suspended mode' (limp home).

Not all fault codes bring on the management light, some codes are monitors which only become active after a certain time or completion of a drive cycle so when a fault code is logged is not necessarily when the fault occurred. For this reason, with the information given it may be possible the engine is already running with retarded ignition and enriched mixture which may or may not explain the O2 sensor high voltage data.

Do you have data for individual cylinder fuel trims? That would be both long term and short term.

At this point- just to rule it out, I think cylinder compression tests should be performed with lumpy cold engine and then a hot smooth engine.
 

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Argh! I checked about wideband sensor voltage and the higher the voltage, the weaker the mixture. My car tended to run in the lower half but in this case, high voltage at idle should be normal as that is when it runs lean (up to 1400-1500rpm).

If O2 sensor faults are being triggered then have a look to see if the induction trunking into the throttle body is ok and there are no leaking breather hoses. If that is ok, have a look at what your MAF reading is. I think around 15kg/hr for warm idle, 100 or so at 60mph or so cruise and 460kg/hr at full throttle around 6400rpm is what it should be.

Make sure there are no leaking air (hissing) sounds from the inlet manifold area also.
 

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Discussion Starter #59
The idle MAF reading is around 15kg/hr as you said and as I wrote earlier sadly my obd disconnects when driving and I still haven't figured out why but my body computer is showing me optional services relay fault. Might be the reason 炉\(銉)/炉. I don't hear any hissing just when I add Gas I hear a sound as if it gulped a lot of air before the rpm raises. Probably sign of the throttle opening so nothing weird. The only 2 bothering sounds are the whining or rather squeaking coming from the engine Bay when starting very cold when the symptoms are the worst - clearly running on 3 cylinders. And a weird sparking like noises coming from area where the throttle and two connectors are located at the rear of the engine. Cant figure out exactly where is it coming from exactly since none of these things can't be unplugged with engine running. Also today the car had problems starting. It started and immediately choked 3 times in a row, then didn't want to start at all so I let the starter to cool down for 15 secs, then the car started so I gave it some Gas and it held itself alive. Fault codes were deleted before the start so no need to think about them causing this.
 

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The noise near throttle body should be investigated. Use something like screen wash hose held to your ear and move other end around to locate the source.

I'd have a look at fuel pressure in various conditions also.
 
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