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Positive (10) ltft all rpm

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4 years 4 months ago - 4 years 4 months ago #35217 by Paul P.
Replied by Paul P. on topic Positive (10) ltft all rpm
In those two pics you just posted , neither your throttle angle nor your mass airflow increased!

How is it possible to achieve 4512 rpm on 15% throttle?

Your Wot test should be done in a safe place with the vehicle in low gear. At WOT you should also be in Open Loop.

Looks like your MAP went to atmosphere which means you are not looking at an obvious breathing issue, and the O2 stayed rich which is good.

But that MAF reading can't be right 2.6 grams/s at 4512.

edit. Also, I looked over your previous posts and at 4400 rpm your MAF was only at 18 grams/s.

Your data shows your MAF to be reading very Low, try cleaning it, and retest to see if the numbers increase.

Either that or whatever your using for live data is giving you wonky readings, I can see its Android-based so you should be really limiting the Pids you view to make sure they update properly and provide relevant information that can be used to make a decision.

Never stop Learning.
Last edit: 4 years 4 months ago by Paul P..

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4 years 4 months ago #35223 by vladislav
Well i didn't know i supose to do the test while driving. In gear.
That's what was scary. I reved the engine to 8k.

I did again the test while driving. Here is the screen recording
photos.app.goo.gl/3KB1KE66VvxU4Ho3A

At the end i was engine braking so o2 got lean.

Everything looks normal to me. Even the car drives normal. The power is there.
Aside from lean fuel trim and the stumble when driving off from still of course.

Also here's a printscreen

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4 years 4 months ago #35226 by Paul P.
Replied by Paul P. on topic Positive (10) ltft all rpm
Those numbers look much, much better!

i still agree with scannerjohn, a vacuum leak for High LTFT at idle and improves with Increased rpm.

You could check the signal voltage of the TPS with a DVOM or scope even better to make sure there is no dead spot off idle., which can cause a hesitation as well.

Your Load should be near 100, its at 77, remember,

Rich O2>Low Load>High Map=Exhaust Restriction

You may have a culmination of things goin on here:

a. partially restricted exhaust
b. Vacuum Leak
c. Lower MAF readings due to partially restricted exhaust, which is why the load isn't closer to 100.

Never stop Learning.

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4 years 4 months ago #35358 by vladislav
Hi!
I did another test and the load goes to 100. See the picture. It may look like the throtle it's not opened all the way but i asure you it is.
I needed to rev the engine all the way past 6k. I didn't know that previously.
So it seems it doesn't have an intake or exhaust restriction.
I don't have any leads again.
Thank you very much for your advices so far. And if you can't think of anything else i will leave it like that. Because i'm sick of it and i have to make peace with my mind.

What could be the worst if i leave it like that in the long term?

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4 years 4 months ago #35362 by Paul P.
Replied by Paul P. on topic Positive (10) ltft all rpm
At this point, I think it would be a good idea to verify that your fuel pressure isn't a little lower than normal, I dont know your fuel spec.

Also, it would be good to verify you have no exhaust leaks prior the Primary O2 sensor.

I still suspect a vacuum leak, your fuel trims support this.

If you can live with it, those trims aren't that bad, I've seen a lot far worse for sure!

Paul

Never stop Learning.

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3 years 10 months ago - 3 years 10 months ago #39650 by vladislav
Hi Paul and John. It's me and my forester again.
It has been a while so i will make a short reintroduction.
Subaru forester 2.0 116kw/168 hp.
Postive ltft/stfl 10% all rpm no load/driving.

After your last reply I was gonna ignore the issue. I ignored it for a 15k miles. But was getting worse. Now it was 14% at idle.
So i got troubleshooting again. I dismantled all the intake and replaced the gaskets or added liquid gasket everywhere. Same results.

I sprayed 2 cans of brake fluid over the engine and tubings. No results. And finnaly...

Paul @Waycraze, you were right. It was a stupid vacuum leak around injector seal. And i had to soak it really well with brake cleaner to get the rpm or trims to react. It was a small leak on the cylinder 3. The same cylinder that had no compression when i bought the car. So the small leak ruined the valve seat because the mix was lean on that cylinder.
Also it was producing knock at lower rpm thus the tumbling i was complaining about.
After i replaced the seals the engine is running smoother and i think it doesn't knock anymore.
But the fuel trims remained the same at idle. And when driving seem to go to zero.

So it seems it ruined the exhaust valve seat again. Do you think it's the case?
If so, can it get better with time? I know it's kinda stupid to hope so, but to get the engine out and redo the head again it's a nightmare. Remember it's a boxer engine, so i can't pull out the head with the engine in the car.

And thank you again for your advices.
Last edit: 3 years 10 months ago by vladislav.

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3 years 10 months ago - 3 years 10 months ago #39656 by juergen.scholl
In the first place it won't help you to know if someone thinks the valve is burned or not, you have to figure it out.....

A burned valve will be most noticable at idle, as a.misfire. The engine won't run smooth. At higher rpm the engine tends to smooth out, given that there is less time per stroke to leak compression. Do you have constant misfires at idle??

First choice is a leakdown test. This will reveal how well the cylinder is sealing.If you can't perform this test you maybe are able to hook a vacuum gauge to the intake manifold and look for a flickering needle.

Finally, a burned valve will not cure itself over time, no way around the necessary repair!

An expert is someone who knows each time more on each time less, until he finally knows absolutely everything about absolutely nothing.
Last edit: 3 years 10 months ago by juergen.scholl.

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3 years 10 months ago - 3 years 10 months ago #39682 by vladislav
Thank you for your reply! I was hoping for a less phylosophical answer. Not trying to be clever here.

It runs smother than before but i guess it feels a bit misfiring when ac compressor kicks in.

Doesn't a oscilating vacuum guage to intake show a intake valve leak?

Leak down tests here are unheard of. And i've seen online for 200$ but still called a compression tester.

Better i will hook up a compressed air machine to the sparkplug hole at top dead center to hear air escaping in the exhaust.

And i don't think it's a burnt exhaust valve. Previous time it was just not closing all the way down. And it had almost no compression at all. It was like the valve seat was worn or the valve lash was inexistent. By valve seat i mean the surface on the head where the valve seats to make seal.

I will try to take the valve cover out with engine in the car to check the valve lash. But it's tight. Changing sparkplugs it'a hassle.

I'm not a native english speaker and maybe i sound stupid.

Thank you for yor advices!
Stay indoors, stay safe!
Last edit: 3 years 10 months ago by vladislav. Reason: corrections

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