Zafira C 1.6 CNG misfire

[alessioblaupunkt]

Zafira C year 2012 (range 2011-2019)

Engine 1.6 ECU LWC1/6L
Petrol with small tank and CNG.

My mechanic did timing belt 1 month ago, 4 new spark plug, coil has been replaced july 2018.

Owner said runs bad only with CNG.
Did a scan and got 2 DTC:
* Misfire cylinder 2
* Multiple random misfire

With that said and previous history, we got no time to test the car
and decided to buy 4 rebuilt CNG injectors.

CNG injectors fitted then we tested the car in street and found
that Owner is a liar:
- car runs bad with petrol
- now car runs really bad with CNG

Did a scan with BrainBee and got 3 DTC:
P0103 MAF high frequency circuit sensor
P2279 Heated lambda signal locked on rich (level2 sensor2)
P0079 Low voltage Circuit intake air temperature sensor

Did a scan with Actia and got 3 DTC:
P0103 MAF high frequency circuit sensor
P2279 Absolute pressure - turbocharger pressure
P0079 Circuit 2 Intake air temperature sensor (low voltage)

Let's start with P2279 that has two meaning, one for BrainBee and other for Actia.

So I checked with Actia and the voltage of the second lambda
is stock to 0.455 V with car at 0 mph with engine off,
engine at idle, engine accelerated, engine cold, engine hot.

Then I checked with BrainBee and the voltage of the second lambda
is stock to 0.641 V with car at 0 mph and engine hot.

Then P0103 with BrainBee, engine hot at idle I have:
Air mass frequency is 1953 Hz engine running with CNG
Air flow 2.88 g/s engine running bad at idle with CNG

Air mass frequency is 1904 Hz engine running with petrol
Air flow 1.41 g/s engine running better at idle with petrol

Is it normal air mass frequency 1900 Hz at idle?
Is it normal Air flow that is twice running on CNG with respect to petrol?
Other readings that I should report?

Then P0079 Circuit 2 Intake air temperature sensor (low voltage)
With engine hot I read 51 Celsius degree with car at 0 mph at idle
and after a run I read 38 Celsius degree with car at 0 mph at idle
There are two sensors in intake manifold, which one is air temperature sensor?
Left or right?

I've found oil in the thread of spark plug number 2
but I did a scan and the cylinder that is misfiring is another one:
BrainBee reads 16 misfire on cylinder 3 during a 20 minutes trip.

Another mechanic took the car and get 100 misfire on cylinder 3.

Tomorrow I will exchange the position of CNG injectors.

[alexandrosts]

Hello my friend, I assume that the cng is fitted at the factory correct ? If so make sure that the wiring harness or the cng you have on is ok, they do suffered on the harness, of course if you have leakie valve cover gasket could course misfiring, but is always good to have your mechanic to check for a good compression, advise manufacture specification for proper compression specs, because lpg and cng they don't have proper lubricant to maintain valves or other metals on good condition and you end up with engine failure, I would start from compression as starters and you go from there

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[autoden]

Not sure about Zafira c but air temp is usually part of MAF sensor.

[Meat-Head]

Sorry, no time to read that.

astra/zafira. Pull plugs out, see if one looks like been shit on. If it does engine bad. Burns oil

[alessioblaupunkt]

So the parts supplier is a silly guy that provided wrong spark plug.
And our more silly mechanic installed them.
In 1 month the wrong spark plug went bad, particularly one was in short circuit.

But that's not all.
Sent to Opil diler fur correct scan and receive correct parts, changed spark plug there and drove back with no problem,
this morning car was in limp mode for P2279 lambda 2 sensor.
Called back Opil diler he told the problem is different from yesterday, and the second lambda will not cause the engine to go in limp mode.
He suggested to change coil pack.
Bought and fitted coil pack this morning, engine running bad as usual, scan gave another error: P2282 temperature and absolute pressure sensor voltage too high.
Bought the sensor that will arrive tomorrow.
And it reads fine in live data.
Let's see tomorrow what else the engine will demand.
Too bad this engine request parts with no end.
Ok me and my mechanic failed to solve the problem, but even that Opil diler returned a car that throws errors the morning after.

---
Answers time:
1) alecsandrosto - Yes the CNG is factory fitted.
2) mehed - Yes has a very little amount of oil expecially in one spark plug.
3) autodan - Absolute pressure sensor and air temp sensor is a all in one sensor with four pins in the intake pipe that goes from the intercooler to the throttle body. Is not part of the MAF.

[autoden]

How many wires go to MAF plug? if its 5 then its got air temp sensor.

[alessioblaupunkt]

Is not coil pack
Is not barometric pressure sensor 2(and air temp sensor)
Is not cng injectors
Is not battery
Is not a compression problem, checked with motometer at cold it's ok.

Advance at idle with petrol goes from -5 to +8 degrees
Advance at idle with CNG goes from -15 to +5 degrees

Obviously at CNG at -15 advance degrees the engine shut off.

If I start the engine it will shut off.
I must keep accelerated.
Once warmed up it could stay at idle with CNG but shaking at idle.
Now I don't have DTC stored or active.

Advance while revving or running is ok.

What cause advance to be wrong at idle?

If I switch to petrol the engine perform better as you can see comparing the advance in the CNG mode.

Don't know what to do.
Have ordered a lot of parts and fault is still here.

[Meat-Head]

ON TOPIC:-

airflow meter, strip loom back 6” feature they break

[Dunker]

Has this got one of those shitty rocker covers on it??? Is it hard to get oil filler cap off when it's running???

[alessioblaupunkt]

Engine has three different behaviour:
*runs bad with misfire at idle on cyl3 or cyl4
*runs ok but while driving at 2000 rpm there is an isssss coming from turbo
or intercooler or related pipes or exhaust
*runs really bad and it could not even keep the idle, it shut off.

No significant difference from petrol to CNG.

DTCs that pops randomly:
P2282: high voltage barometric pressure sensor circuit (BARO 2)
P0300: irregular ignition
P0303: irregular ignition cylinder 3

I've sprayed water on valve cover, on coil, under coil, intake manifold,
turbocharged, oil recirculation pipe, NO CHANGE in engine behaviour.

I've disconnected and clogged oil recirculation pipe on valve cover and
the relative pipe that goes to the left (intake manifold) and to the right
(small idle valve?) the result is the engine start to smoke gray/light blue
maybe because there is fuel excess.

By the way I reconnected everything and when the engine runs bad
that could not even stay at idle, the lambda 1 voltage is 2.3V
when engine runs normally lambda 1 voltage is near 1.49V

If I disconnect lambda 1, engine will shut off in 3 seconds.
Then I can start it but if I don't accelerate it will shut off immediately.
And the appropriate DTC will appear in ECU memory.

If there is an intermittent air leak it will be hard to find.

Remember that CNG injectors are new.
I've changed coil but it is not responsable, and refitted the previous.
I've changed the barometric pressure sensor but it is not responsable,
and refitted the previous.
Spark plugs are new and original.

@Dunker:
Has this got one of those shitty rocker covers on it???
YES, it has.
Is it hard to get oil filler cap off when it's running???
ABSOLUTELY YES, it is!
I will wait for other Dunker question!

[Meat-Head]

If the lambarda sensor is giving more than 1 volt

1) your meter lieing
2) lieung
3) your computer lieing

[Dunker]

Try new rocker cover. They crack internally. U can't usually see crack. They're about 40 quid on eBay. When faulty can cause misfires, uneven running, allsorts of weird shit. Fuel trims are very odd as well.

[alessioblaupunkt]

My mechanic don't want to believe me and Dunker and he ordered another coil pack of another brand.
He will lose time and money.

If the engine run regularly while driving at 2000 rpm
there is an issss from the turbo/intercooler and near that area,
so today I removed the bumper to inspect the intercooler and found nothing usefull apart the driver hit the bottom
of the car in the intercooler area. No damage at all.
Intercooler pipes are ok too.

Will check for MAF wiring as suggested.
Don't know if at idle MAF 6.88 grams/stroke is a normal reading or not
running on petrol with engine a little warm, say 70 C degrees.

Obviously a new MAF will be out of discussion as the rocket cover, for price tag.
The rule no money no fix is still valid.

[alessioblaupunkt]

Big news:
since thursday engine is in a permanent fault: cyl 3 misfire

if coil is connected there are sparks in cyl 1,2,4.
if coil is disconnected there are the 4 pulses from ECU.

Same behaviour with a brand new coil.

So ECU is damaged and in the next days I'll se if I can open it.

[abdulsattar]

Regarding your lambda 2 error code
If voltage of o2 Sensor no 2 is jumping when engine is running it means that your catalytic converter has gone bad. You should try new o2 sensor first. They become slow when ageing.
Also check wiring harness of cng injection thoroughly