Cuore L251 - Noisy Engine and Loss of Power

[bluedog]

I don't blame you for that, anyway, its your choice of how to treat engines. It's just that it's you too, who has to live with the consequences... It's just a "no wonder" from my side and a warning towards you, because I suppose you might like to save some time and money, perhaps. So, you do not really have to apologize. It's only a hint, to say, that this driving style is not quite normal.

But at least, make sure you use very good engine Oil and you change it regularly... that is, then, a must.

[terios]

Upshifting at 2500 - 3000 rpm is good, but at 4000 - 4500 is not bad too. We are still in the tolerable range of the engine, I'm convinced about that. My previous Yaris doing already 160.000 km still runs perfectly at very high revs with nearly zero oil consumption, no smokes, never failed or been major repaired.

May be you're right when talking about small engines < 1.0L.

Now, back to the facts of this car:

First time I changed the oil engine in a dealer shop, they put semi-synthetic 10W40. I was not satisfied about it, and then decided to change it again, for a full synthetic 5W40, but this time I've putted before an additive for cleaning the engine before the change. The result is kind of oil very black and thick... this car seems to be very bad treated before!

[bluedog]

Is that cleaning stuff still in there?

[terios]

No, I put it just before the change with the old oil, warm up the engine 15min and then discharged. Now, is the pure oil only.

Something wrong?

[terios]

Zitat von bluedog

Das finde ich auch merkwürdig.

Die Schaltpunkte sind zu spät, jedenfalls für die Strassenverhältnisse Europas. Wie es auf ner algerischen Sandpiste zu fahren ist, weiss ich nicht. Ich kann mir aber vorstellen, dass man dann rausholt was drin ist, besonders wenn der Motor so schwach zieht, dass man nicht über 100km/h kommt.

@terios: There is enough Space to work.

You can measure the shims, but to replace them, the camshaft has to be taken out.

Kokomiko (and me too) are astonished about how late you are upshifting. At 30km/h, he would shift into 3rd gear already. Further, Kokomiko asks, if valve clearence was never checked before.

If no, that alone would not be alarming to me, but in combination with the high revolutions driving you obviously do, it could be at high time to check valve clearance.

You can find tons of pictures from inside that engine here:

http://www.daihatsu-forum.de/vbullet...benringe+rotzi

That is a tread, where our higly estimated user Rotzi documented a piston rings replacement, and he ended up in a more or less full engine restoration.

An Idea from myself: Did you check if the fuel pressure is ok? Because once, when I had a weak fuel pump, I noticed a slowly increasing lack of power too... but that would not explain the engine noise.

Is the engine running smoothly, or is it bucking? If it doesn't run smootly, I'd try a replacement of the spark plugs... but this is for sure not the reason of the noise from the Engine too.

To answer your questions: Kokomiko and bluedog.

I'm not sure if the previous owners have adjusted already the clearance or not? or even if they openned the engine or not? Do you know how to confirm about that?

How to know about tue pressure of the fuel? I'm sure of one thing, till 100km/h the car is quiete fast.

Is it the knock sensor who makes the car slowing down at high revs because, for exemple, of bad fuel? I'm using unleaded 95.

[bluedog]

As far as I know, there is no way to determine, if valve clearance was checked in the past. You're lucky if you have precise maintenance record for that.

But with no other clue, assume it was never done.

That engine does not have a nock sensor. That is made with the spark plugs, and besides that, the engine needs only a 91octane unlead fuel as minimum requirement.

So, if you suspect something to be wrong with the nock sensing, then first would be new spark plugs.

Or you could take a look at ignition timing. To do that, you would set the Bridge at the OBD-Socket according to the Graphic under the engine hood, which you photographed, and then use a ignition timing stroboscope (sorry, I could not find the official expression for that in the dictionary - I hope, you guess what I mean...).

Something I forgot to translate before: Are you sure the clutch/transmission is ok?

[terios]

Zitat von bluedog

That engine does not have a nock sensor. That is made with the spark plugs, and besides that, the engine needs only a 91octane unlead fuel as minimum requirement.

Could you please more explain that point, how this engine protects itself from knocking especially when we know its compression ratio is quite high 10:1?

You know in my country regulations are not severe as in Europe; so may be even 95 is not enough. But the other Cuores, with less noisy engines are still using the same fuel as me! Well, when I come back home I'll try to add a kind of fuel octane booster, and see what happens... ok?

Zitat von bluedog

Or you could take a look at ignition timing. To do that, you would set the Bridge at the OBD-Socket according to the Graphic under the engine hood, which you photographed, and then use a ignition timing stroboscope (sorry, I could not find the official expression for that in the dictionary - I hope, you guess what I mean

Unfortunately, I don't have Timing light and not well equipped at all. I'll try a scan and see. Thanks.

Zitat von bluedog

Something I forgot to translate before: Are you sure the clutch/transmission is ok?

The clutch is good (well, I feel the release bearing hissing a bit) do you suspect a bad 5th gear? Don't know how to check about it.

[terios]

By the way, the link you gave me is very interesting in terms of pictures of course (the content is a bit confusing for me lol) Is it mendatory to change the head cylider cover seal after clearance inspection?

[bluedog]

The nock protection is based on ion current measurement technology. I do not know more about that, then that it needs the correct spark plugs to work.

But anyway, I don't suspect that too low octane fuel is the problem as long as you use 95octane labelled fuel. Even outside Europe, the difference should not be that great. It is more probable, that you have contaminated Fuel or Water in it or so. But even that should not be a Problem, as long as the Engine runs smoothly. It may just rise fuel consumption...

But if there is to much dirt or Sand in the tank, that could be a Problem, but I do not considder that very probable.

To check that, you would be forced to look at the fuel pump inlet. There is a strainer at the Inlet... But to get to it, you would be forced to take the pump out of the tank and for that, you'd have to drain the fuel and detach the fuel tank first.

So it is maybe easier to measure fuel pressure, which is done by mounting a pressure gauge intoto the fuel supply hose. Measure that near the engine. You need to know what pressure you get right at the engine, not near the feeding pump in or just outside the fuel tank.

But, I recommend to replace the spark plugs first, if not done yet. That's far easier.

Lunch time. More that afternoon.

[bluedog]

I do not suspect a problem with the 5. gear, because you said, the noise you hear is related to rpm and not to a specific gear. If, then it should be the clutch, which I do not believe in. If it was the clutch, you would have problems in lower gears too, e.g. from the 3rd on or so.

And, last, but not least: That would not explain a rpm-related noise from the engine that leads you to suspect the valves to make noise.