Fiat Tipo(Egea) 1.6 Multijet DIESEL fuel consumption and weird OBD readings

[cac]

hi

1. Introduction
a year ago (January 2018) I’ve bought brand new Fiat TIPO (aka EGEA in some countries) with 1.6 Multijet2 diesel engine (120 hp). I’ve decided to buy this particular car becouse:
– I needed a new car (thought it will keep me out of garage – silly me)
– I drive at least 100 km every day in big distances (30-50 km at once mostly, no short distance like 3-5 km at all), I live in the country so mostly drive on no-traffic roads – so I did expect low fuel consumption. I have to mention that I drive mostly same roads every day and speed is between 90-120kmph – mostly.

But Murphy’s law was just waiting for me. Here’s short story of my car, dealer’s “mechanics”, and couple of question I can’t find answers anywhere – if anyone could help, will be gratefull.

2. The story
Since day one fuel consumption was stuck at 6.4liter/ 100km – no matter what. This value didn’t change if I was driving 90kmph, 130 kmph, 180kmph – every single tank I measured it dividing tanked liters per milage and it always was 6.4. What’s interesting computer’s calculations are very accurate, and always matches mine’s.

First of all I was expecting something around 5 liters consumption buying this car, let’s say 5.5 tops. But when I checked that speed does not affect fuel consumption at all I knew there is something really wrong with the car. I’ve visited ASO (that’s name of dealer’s garage in Poland – not sure how to translate it so I’ll stick to that name) so they check if everything is ok – of course they confirmed that the car is running properly, and I must be driving with “heavy foot”. At that point I report them other strange behaviour: sometimes when driving at steady speeds (let’s say 120kmph) when I try to accelerate and push pedal more, car does not respond to this for 3-4 seconds (no speeding up, steady rpm), and then suddenly it accelerates. It was very frustrating especially while overtaking – ASO answer to this was turbo lag :/ It happend only few times so I didn’t push them on this.

After first 5000km suddenly “check engine” lit out of nothing on my dashborad. The car was driving like before, but I had point to argue with ASO now. They connected some scan tool to car’s computer and said that the throttle is reporting too high voltage (remember this for later!) so it needs to be replaced. They did replaced the throttle, and guess what? No more turbo lag anymore, and fuel consuption changed but not yet in expected way. Since this repair every single tank was 6.2 but if drove rougher (150-180) – it could rise up to 6.6. So it dropped a little, and become speed-dependent – looks more realistic so I burried the hatchet thinking that consumes 6.2 at it’s best.

After passing 14000km the miracle occured! The car started to consume 5.7 out of blue! every single tank was 5.7 just like this! Nothing changed – same fuel on same gas station, same roads, same weather. And suddenly it drops? This state kept for about 8 full tanks as I remember. Then it bumped up to 6.0 with no reason, like before!

At 20k km there was a car inspection I had to make at ASO (due to guarantee restrictions) so I had chance to talk to mechanic why car is acting like this- again he said “everything is fine, I’ve checked on computer”, little lier 😉 But when on inspection I report them another problem – steering wheel was knocking when turning – they diagnosed that the power steering engine is faulty (there is electrical in my case), and they don’t have one so they need to order it in factory, and it will take some time.
At this point I suspected that mechanic didn’t check computer readings or was too lazy to diagnose weird readings or , what is most likely in my opinion – lack of knowledge stopped him.
But I had 2 months till they get the spare part so I bought OBD interface and couple of software tools to read it and started digging what my car is reporting. In this time I’ve generated tons of files with all my computer readings and found some really strange readings.

It’s very hard to find any reliable instructions and expected values for 99% of OBD readings. Second thing is, when I found something it appeals mostly to gasoline engines which vary a lot from diesel ones. So at this point if you want to answer any of my below questions and you are not familiar with diesel engines, please don’t 🙂

From the things I could compare to other diesel cars and found in internet’s deepest corners I created charts from OBD readings for my ASO showing:
– that my throttle reports opposite values to any other car. My car shows 85% when idle, and 5% when driving ( as far as I know it should show how open it is, not how close right?)
– my throttle is closing suddenly while driving for a few seconds – in diesel it should not close ever while driving right?
– my CEL (calculated engine load) shows around 35% when idle (warm engine, AC off) – looks too high to me – any other car had around 20%

I delivered them all that data when the power steering part arrived, and…. another miracle occured.
they did programmed injection, they did programmed the main computer (not sure about this becouse my obd program shows they did not – let’s say they claim they did) and here is what changed:
– car starts to accelerate like never before – now I can say there is 120 hp, felt like 90 before
– fuel consumptions dropped to 5.4 even when city driving!

But this state last for 4 full tanks only. After that the accelration is better then before programming but not that good, car accelerates better over 3k rpm then between 2-3 which is very odd, and fuel consumption 6-6.1 – can’t go below. Sometimes car runs properly (smooth driving, good accelaration) and fc drops, and sometimes not. Average is about 6.0 out of it -all the time.

3. The questions

I’m not mechanic. I can’t use any unauthorized garage or change anything in the car myself due to guarantee. My point is to show ASO that car’s computer reports problems (weird readings) so they would have to fix it.

PLEASE remember this is DIESEL engine.

1. my ECU reports 5 temperature sensors that indicates -40 C degrees. I’ve contaced 2 OBD software companies why is that, and they claim that there is no such sensor in my car so ECU returns default value. Why ECU reports values for sensors that does not exist at all?

2. My throttle is closing while driving (mentioned above, happens eveyr day, several times a day) for a couple of seconds – why? Shouldn’t it stay open all the time in diesel? BUT when outside temperature drops below 5C degree , this does not occure , instead I’ve got EGR error constantly about 50%. THE EGR Error is reporting when egr commanded is 0! How can it be that EGR is being opened when it is not even commaneded to, but only when temperature drops below 5C?

3. Is it right that ECU reports 85% for throttle @ idle, and 5% when driving? Shouldn’t it be oppposite?

4. In obd readings I have “Oxygen sensor wide range current mA” and “Oxygen sensor wide range equivalence ratio”. Should this positions show relative values?becouse they don’t. Is this one sensor presented in two notations or 2 different sensors? How should I interprete it?

In mA position I have noticed that sometimes it operates 1-2mA (2mA is when driving and take my leg out of pedal), and sometimes it operates in 1-2,52 mA – how so? (think that 2,52 occures after dpf burnout, bot not sure for 100%). btw my dpf burns out every 300-400 km – is it normal? Fuel consumption jumps up to 9l/100km while this procedure.

5. what’s proper MAP value at idle for diesel engine?

I’ve noticed that when high(normal in my case 🙁 ) fc occures :
– MAP indicates about 95 – my barometric is 100 btw.
– MAF indicates about 6 g
– CEL about 30%

but if car’s driving well (and fc drops down) at idle:
– MAP shows around 92
– MAF shows around 10g
– CEL is about 22%

Some additional info:
– unfortunately my car does not report LTFT or STFT – I have to base on other parameters
– no error codes are reported (besides check engine which was cleared after throttle replacement) from ECU
– I have both MAF and MAP sensors
– every readings presented done on warm engine of course
– I’ve spoken to couple mechanics in different garages – non of them known how exactly diesel engine works and what values to be expected in OBD readings. I’ve written to few mechanics, chip-tuning forums – all I got was no answer or petrol-engine based answer which does not apply in my case.

thanks in advance
Kacper

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