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[jandroa]

Hi everyone! Opel Omega 2.6 V6 (Y26SE) owner here. Some weeks ago my Omega check engine light came on. The errors codes were P0170 and P0173 (Fuel Trim Malfunction Bank 1 & 2). I inmediately took the car to the official Opel workshop in my town. They had the car for about a week and did all sort of tests, but they didn't found anything wrong, so they just erased the error code to turn off the check engine light. I was told that the lambda sensor data was OK. They returned the car to me, and only 50km later, the check engine light is back.

The car is running right and there is nothing wrong in terms of functioning, performance or noises.

Should I be concerned about it? Do you have any experience with this issue and know what could be the reason behind the check engine light?

I would be grateful if you could point me in the right direction.

Thank you in advance.
Alex.

Edit: Add more information.

[TheBoy]

Does the car run on LPG? If so, might need to get LPG remapped.

Does the car have an aftermarket oiled air filter? If so, pop a stock one on.


Otherwise, are the trims high or low (positive or negative on a 2.6/3.2, or less or more than 127 on an older one).  Ideally you need to read the live data off it for the LTFT, and also the MAF

If you don't have the capability to obtain live data, check for air leaks in the intake system, ir exhaust leaks around or near the manifolds.

[jandroa]

Thank you for the suggestions!

The car runs on petrol (E10) and as far as I know the air filter is original (last change was done at the official Opel workshop a couple of years ago).

Today I got a cheap scanner to read some live data from the OBD2 port. The STFT was fine, making small corrections but always very close to 0.0 (both above and below zero). However, the LTFT showed the value at 25 which I think is very high. I guess this is the maximum value until the check engine light activates. The strange thing is that the car behaved well, with no apparent signs of air leaks.

The MAF sensor values were fine  (I am far from being an expert), 2.3 at idle.

Thank you!

[grifter]

My 2.6 runs on E10 ok, but it seemed that the lamdba code came up a lot more with e10, so I just use e5, if on occassion it does come on I just disconnect the battery for a while. Fuel consupmtion also much higher on E10.

[TheBoy]

The MAF sensor values were fine  (I am far from being an expert), 2.3 at idle.

The correct reading for a 2.6's MAF at idle is about 12kg/hr, which is:
12,000/60 = 200g/min
200/60 = 3.33g/sec
(assuming my maths is right)

2.3 (presumably) g/s = 8.2kg/hr, which seems a little low to me.  Which usually means unmetered air getting in by not going through MAF (or MAF has developed a fault, though Omega MAF's are bomb proof if not oiled by a filter or sprayed with cleaners)


And, yes, around 25% of trim (+ve or -ve) is where it brings on a trim malfunction.

[jandroa]

My 2.6 runs on E10 ok, but it seemed that the lamdba code came up a lot more with e10, so I just use e5, if on occassion it does come on I just disconnect the battery for a while. Fuel consupmtion also much higher on E10.

That is interesting, I never though E5 comsumption would be lower than E10. I will give a try!

The correct reading for a 2.6's MAF at idle is about 12kg/hr, which is:
12,000/60 = 200g/min
200/60 = 3.33g/sec
(assuming my maths is right)

2.3 (presumably) g/s = 8.2kg/hr, which seems a little low to me.  Which usually means unmetered air getting in by not going through MAF (or MAF has developed a fault, though Omega MAF's are bomb proof if not oiled by a filter or sprayed with cleaners)


And, yes, around 25% of trim (+ve or -ve) is where it brings on a trim malfunction.

That is a little bit confusing to me because the MAF says the airflow is a little low but the LTFT at 25% says it has a lot of air so it's injecting more fuel, isn't it? As you said, maybe the unmetered air is not passing through the MAF or the MAF has developed a fault.

I will ask the mechanic to check the MAF, the lambda sensor and if there is any point where air can enter, a damaged hose or something like that.

Thank you!

[TheBoy]

That is a little bit confusing to me because the MAF says the airflow is a little low but the LTFT at 25% says it has a lot of air so it's injecting more fuel, isn't it? As you said, maybe the unmetered air is not passing through the MAF or the MAF has developed a fault.

Its a petrol engined closed loop system so...

It injects fuel based on incoming air.  The lamdas detect its running too lean, because more air is coming in that it thinks, so ecu increases trim (increases injector duration).

[mong00sehun]

hi,
i have a 2.6 too, and i had this error code around one month ago
this occoured when i had a just little amount of fuel in the tank and i drove on serpentine roads, when i think the fuel is was too low, and and the pump cannot recivie the right quantity.
i refulled and i dont have this code anymore

[jandroa]

Its a petrol engined closed loop system so...

It injects fuel based on incoming air.  The lamdas detect its running too lean, because more air is coming in that it thinks, so ecu increases trim (increases injector duration).

Ok, I will erase the error code and check again if the LTFT rises.

hi,
i have a 2.6 too, and i had this error code around one month ago
this occoured when i had a just little amount of fuel in the tank and i drove on serpentine roads, when i think the fuel is was too low, and and the pump cannot recivie the right quantity.
i refulled and i dont have this code anymore

Thank you for your information, I will ensure that my tank is not too low 

[jandroa]

Hi everyone, after clearing the error code and driving for a few hours, the check engine light does not come on, but if I connect the OBD scanner it shows me the error codes P0170 and P0173 again.

The car is running as always, there are no significant changes in rpms at idle, no loss of power when accelerating...nothing unusual.

Checking the scanner measurements again it shows me the following data:

RPM (at idle): around 650rpm
MAF (g/s): 3.5
STFT1 and 2, changing between -3% and 3%.
LTFT 1 and 2: 25%
O2B1S1: changing between 0,085 and 0,900
O2B1S2: around 0,700
O2B2S1 and S2: similar values than B1.

If the car had an air leak, shouldn't it be noticeable in the rpms at idle, or even when the car moves? Can a faulty sensor bring the LTFT to 25% even if the car is running properly?

Thank you!!

[jandroa]

Additional info: I have seen that besides de STFT is ok at idle, as soon as the rpm goes higher, the STFT goes above 14-15, making the LTFT reach 25 at the long term.

[TheBoy]

Reset fault codes (which on a 2.6, if there is a stored code, should reset the BLMs)

Confirm LTFT is 0%, and stays at 0% when idling for a few minutes.

Increase revs, and see if LTFTs rise. And if both banks rise at around same rate.


I'm wondering if its sucking unmetered air, but only at higher revs.

[TheBoy]

Also worth checking that the B!&2 Sensor 1's are flicking between rich and lean at about 1Hz once it goes closed loop.  On the Tech2, this figure is called ratio, but might be called something else on other scanners.

If its not alternating, or doing so slowly, this can be a sign of a tired sensor.

[jandroa]

Reset fault codes (which on a 2.6, if there is a stored code, should reset the BLMs)

Confirm LTFT is 0%, and stays at 0% when idling for a few minutes.

Increase revs, and see if LTFTs rise. And if both banks rise at around same rate.


I'm wondering if its sucking unmetered air, but only at higher revs.

This is exactly how it worked, resetting the fault codes put the LTFT at 0%. When idle, LTFT remained at 0% and STFT varied between -3%, +3%. When I increased revs to 2000 and held it for about three minutes, STFT went up to 14-18%, and LTFT began to increase, both banks at the same rate, up to 0,8%.

As you said, it seems to be sucking unmetered air only at higher revs, at idle it's ok.

Also worth checking that the B!&2 Sensor 1's are flicking between rich and lean at about 1Hz once it goes closed loop.  On the Tech2, this figure is called ratio, but might be called something else on other scanners.

If its not alternating, or doing so slowly, this can be a sign of a tired sensor.

As for the B1&2 sensor, I am afraid my cheap scanner is not giving me the ratio or anything like that, just the voltage.

[polilara]

https://www.omegaowners.com/forum/index.php?topic=149556.0;all

If you check this you can see my Y26SE with old and new sensors, mV...

[jandroa]

We found a disconnected small tube near the intake manifold with a smoke machine. We have put it back in and now we have to drive the car to see if the consumption returns to normal.

[Doctor Gollum]

That's the vacuum line between the throttle body and the fuel pressure regulator.

Really easy to miss if you remove the TB or plenum as it will fall out on a whim if disturbed.

[jandroa]

Hello everyone, despite the repair, the car continues to use a lot of fuel. The mechanic told me that it may take time to stabilize consumption after repairing the vacuum leak, is this normal?

I have reset the LTFT values as well as the average consumption calculated in the on-board computer.

Thanks!

[TheBoy]

If you reset trims, it should learn the new values, which should be 0%, within a couple of miles, then refine constinuously.

[Doctor Gollum]

Would running the fuel pressure regulator without a vacuum potentially damage the diaphragm

[cam.in.head]

it shouldnt do as the spring will be holding it closed and if the diapragm split you would know about it with pressurised fuel squirting out of it ( the vac port)

[Doctor Gollum]

it shouldnt do as the spring will be holding it closed and if the diapragm split you would know about it with pressurised fuel squirting out of it ( the vac port)

Would that count as over fuelling if it was being hoovered in by the throttle body

[cam.in.head]

definately but it would be sending in a heck of a lot unless its a slight pinhole
with the engine running (or pump) nothing  should be coming out of there ! 

[jandroa]

If you reset trims, it should learn the new values, which should be 0%, within a couple of miles, then refine constinuously.

I will check if it learn the new values and keep them consistently near 0%.

definately but it would be sending in a heck of a lot unless its a slight pinhole
with the engine running (or pump) nothing  should be coming out of there ! 

That sort of things should be easy to notice, isn't it?

[Doctor Gollum]

Is the high fuel consumption a new thing having driven the car 1,000s of kilometres? Or is it high compared to previous/other cars you have?

9.4l/100km would be a reasonable good average, significantly higher if you only drive short distances or around town.

[jandroa]

Fuel consumption of this car used to be about 10,5l/100km (with 1000s of kilometers driven in the past), now it has increased to 15-16l (it fluctuates a lot because since the car was repaired I have not driven enough kilometers to let the car calculate a consistent average).

Is it true that since the repair I have only driven short distances in town. Maybe all I need is to wait and drive more (especially out of town).

[polilara]

I sometimes check the (minimum) fuel consumption of my 2.6 Elegance so that I go to highway and accelerate to 85 km/hour, put cruise on and reset the average fuel consumption value from the car display. After a couple of kilometers I can see average consumption below 9 litres/100km. Can you do this in your Omega and have you tested this?

[jandroa]

That's a great idea, I'll check it out as soon as possible.

Driving in town now it has a very strange behaviour (at least for me), if I reset the average fuel comsumption and drive at a stable speed, the average consumption goes down, but when I stop the car at a traffic light, the average comsumption starts to increase again.

I will get back with the result of this test.

[Doctor Gollum]

That's a great idea, I'll check it out as soon as possible.

Driving in town now it has a very strange behaviour (at least for me), if I reset the average fuel comsumption and drive at a stable speed, the average consumption goes down, but when I stop the car at a traffic light, the average comsumption starts to increase again.

I will get back with the result of this test.

That's down to how the computer works. It sees the fuel flow/speed. When speed is Zero  it can't accurately process the fuel consumption, so the consumption becomes a poor guesstimate.

Also, cold start enrichment cripples the consumption until the engine is up to temperature, so a car that is only driven 12-16km from cold will never warm up properly and will severely impact the fuel economy of one that is driven for some time.

The difference in fuel used between a cold start  journey of 12km vs one of 24 is negligible.

Point being that if the fuel consumption is within the range of other Omegas, then it's something that you can either live with or not, but if it's significantly worse then consider the various temperature sensors and the thermostat.

[jandroa]

Thank you so much for the explanation, it all makes sense to me now.

I'll try to do the test that @polilara told me and also wait until I have driven a significant number of kilometers excluding short distances in town which are not representative of the car's real average fuel consumption.

[olm]

Hello, I take advantage of the topic to comment that for a few days I also have problems with high LTFT. Suddenly I observed an increase in consumption and the LTFT values ​​are over 10-14%. I have checked the vacuum lines and everything seems to be fine, the lambda probes have 45,000 km but it is rare for both to break at the same time. The MAF has about 30,000 km, it seems strange to me that it fails so soon. Any ideas on what to start looking at?

[jandroa]

Hello, I take advantage of the topic to comment that for a few days I also have problems with high LTFT. Suddenly I observed an increase in consumption and the LTFT values ​​are over 10-14%. I have checked the vacuum lines and everything seems to be fine, the lambda probes have 45,000 km but it is rare for both to break at the same time. The MAF has about 30,000 km, it seems strange to me that it fails so soon. Any ideas on what to start looking at?

In my case all vacuum lines seemed to be fine, until the mechanic checked them with a smoke machine, maybe you can check it too the same way.

[jandroa]

We are back to the problem, the errors P0170 and P0173 have appeared again, I will take it to the mechanic to have it checked again. The vacuum leak (loose tube) has already been repaired, since then about 300km have been driven.

[jandroa]

The first lambda sensor will be changed next tuesday, I will post the results after that.