Uneven idle, mostly warm - and fault code ECM-250A upper limit

Orchid70 · Post by **Orchid70** » 02 Jan 2020, 13:44

V70 from 2001 - non turbo B5244S2

My friend bought it last summer and it had the fault code already then. Allthough it did not have that uneven idle - not that much as know.
ECM 250S upper limit is the fault code

The fault always comes up with warm engine - closed loop - at 75-90 km/h is what I find in the memory

The warmer the engine the ruffer the idle

I have checked with working used MAF sensor - no change
I have changed the first lambda sensor - Denso, new
I have changed vacuum lines earlier
I changed EVAP valve with working used
When I tried to do the short test in VIDA for EVAP/fuel leaks - I couldnt start it. So I went to the manual starts of EVAP purge valve 25% and for the EVAP valve shut off. After playing with them for a while - the leak test could be started - result was NO FAULT codes.
But when I played with the manual start of the EVAP valve - I noticed that the idle got smooth.
So I filmed this:

The only symptom we can feel, other than the idle, thats getting worse - is that at cold start, the fuel consumption is up to 99,9L /100 km (the normal would be below 50L /100km at cold start at around 5 pöus Celsius). He doesnt know what the actuall consumption is - but the car computer tells its 8L /100 km

Im at loss and dont know where to start measuring next.
I have VIDA and I have oscillsocope to use.
I do not have a smoke machine.

One question comes in mind - what happens if the EVAP canister gets "full"?
Or perhaps - the EVAP behavior is due to something else?
We have sprayed carb clean everywhere around the engine and couldnt see any change on the idle. In the same time tha is hard - becasue all of the sudden the idle gets ruff on its own - so at one time I felt there was a leak in the inlett gasget - but I couldnt repeat it.

Thankfull for any input

Post by **RickHaleParker** » 03 Jan 2020, 08:02

If it is ECM-250A upper limit. Smoke test the intake system and check fuel pressure. Did you clean the MAF sensor on the test unit?

Fuel line pressure Desired value:
Relative pressure 380 kPa
Absolute pressure 480 kPa

You might be able to find air leaks with starting fluid. Spray the fluid around. If there is a leak, it will suck in the fluid and you will hear the engine surge. Do not miss the Intake manifold gasket as well as the rest of the plumbing.

Google DIY Smoke machine. There are lots of ways to make a smoke machine. One member here burn Sage in a jar to produce the smoke ... at least we think it is Sage, he is a little strange after he does his smoke test.

The stuff you are messing with is for ECM-250A lower limit.

Upper limit:

Damaged mass air flow (MAF) sensor
Low fuel pressure
Air leakage.

Lower limit:

Damaged mass air flow (MAF) sensor
High fuel pressure
Leaking injectors
Leaking evaporative emission system (EVAP)
Contaminated engine oil
Oil level too high.

Orchid70 · Post by **Orchid70** » 03 Jan 2020, 13:10

Thank you dearest!
Yes - I used MAF cleaner from Liqui Moly on both MAF sensors. And the sensor outputs are not specially much off, compared to the desired values by Vida.
When he bought the car last summer - there was also a MAF sensor fault code (ECM-150A - MAF - upper limit) present, that havent appeared back after cleaning his MAF, that wasnt that dirty from the start, together with the ECM-250A-upper limit.

It deffinetly feels like air leak - one or the other way. But I could not get any reaction on engine surge. I thought it happened ones - but the engine is surging on its own so it was hard to repeat it. I used brake cleaner.

Ill try to measure the fuel pressure.
And make a smoke maskine =) Perhaps not use Sage - I dont have it - but I have Thyme....
I found this video and have made my own glass jar.

Tomorrow its time to see if it works.

By the way - what does "Relative pressure" and "Absolute pressure" mean?

Post by **RickHaleParker** » 03 Jan 2020, 16:23

Orchid70 wrote: ↑03 Jan 2020, 13:10 By the way - what does "Relative pressure" and "Absolute pressure" mean?

The difference is the reference pressure (the datum).
Absolute pressure the datum is a perfect vacuum like you find in outer space. (Absolute zero pressure).
Relative pressure the datum is atmospheric pressure at sea-level. (100 kPa above Absolute zero).

Absolute pressure is the measured pressure compared to Absolute zero.
Relative pressure is the measured pressure compared to the ideal atmospheric pressure at sea-level.

Orchid70 · Post by **Orchid70** » 03 Jan 2020, 17:31

Only Volvo bothers to even mention something so unreal as the Absolute pressure - why in earth??
Or you need to calculate your relative presure depending on the atmospheric pressure and depending on how high above the sea level you are at. Who does that? Or do they give you the formula to calculate the preferable pressure? =/ Hm need to find out my sea level hight....
OK - so something around 380 kPa - is what Im looking at.
Thank you!!

Post by **abscate** » 04 Jan 2020, 03:53

We live in a sea of gas of near constant pressure of 950-1000 Kapaa, but our engines don’t.

The intake manifold starts at 100 kPa when we start our car in the morning

Idle manifold pressure about 40 kPa

80 kPa when we start driving

150-200 kPa when we boost to get onto the highway.

The system for fuel delivery has to deliver a fuel pressure at the injectors for all those conditions.

Orchid70 · Post by **Orchid70** » 06 Jan 2020, 13:58

Thank you abscate!

That version of smoke machine did not work - the plastic pieces melted because I didnt find any leaks. It perhaps works if there is a big leak like in the video above. But not for small, hard to find, ones.
So just to be sure and for future neads - Ill make one with a paint bucket with Kanthal wire and torch wicks thats is heated with a battery, and proper air hose mountings with quick 1/4 air fittings.Thats hapening tomorrow.

In the meanwhile - I have tested the fuel pressure and injectors.
The bad battery made the manometer to fluctuate:

After the battey change - it was steady. Perhaps a bit low pressure???
I havent been able to find fuel pressure in VIDA - only fuel tank pressure.

After the battery change - the engine is better in "picking itself up" again. It doesnt get stuck in the fluctuating state.

Then I checked the injectors - all look good:
from the 1 to the 5:th:

See how the injectors compensate for the erratic engine speed:

If the smoke test wont find anything - then Im at lost.

Here are the lambda sensor measurements with SnapOn (pdf file) -During drive.
Isnt the second lamda a bit too erratic?

victor lambda.pdf: (28.56 KiB) Downloaded 213 times

Thank you all!!

Post by **RickHaleParker** » 06 Jan 2020, 14:30

Orchid70 wrote: ↑06 Jan 2020, 13:58 I havent been able to find fuel pressure in VIDA - only fuel tank pressure.

Orchid70 · Post by **Orchid70** » 06 Jan 2020, 14:33

Yes I do know what it should be - but I havent been able to find the real time measurement - perhaps there is no??

Post by **abscate** » 06 Jan 2020, 18:32

We might be losing your meaning in translation

The fuel pressure should sit at 3.8 bar, constant

Your video shows it is perfect.