Intake pressure waveform issue

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Intake pressure waveform issue

Postby victor2k » Thu Oct 27, 2016 7:05 am

Hello,
I have a 2004 Avensis 1ZZ engine type with the idle issue(the engine stall and sometime stop after warming phase)
No faults in error memory,the throtlle body was replaced without any improvement.
The oxigen sensor,maf,knock sensor was disconnected to disable lambda regulation,advance control-without any improvement.
The measured compression was:10,13,12,13 bar(the minimum compression is 10 bar).
The valve clearance is ok:0.25 mm / intake and 0.35 mm /exhaust.
I made some registrations for cylinder 1,intake,crankcase pressure and I need help :at intake pressure the pulsations have different duration and amplitude from one cylinder to another.Can be the influence of compression?
Here is my recorded data.
Thank you
Attachments
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Toyota_Avensis_2004_20161026-0001.psdata
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Last edited by victor2k on Sat Oct 29, 2016 6:32 am, edited 1 time in total.
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Re: Intake pressure waveform issue

Postby steevegt » Thu Oct 27, 2016 10:13 am

Try to do that test without having one cylinder disabled.
The extra volume in that cylinder, from the compression hose, could be causing that.

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Re: Intake pressure waveform issue

Postby STC » Thu Oct 27, 2016 1:37 pm

Hi Vicktor.

The measured compression was:10,13,12,13 bar(the minimum compression is 10 bar).


IF the minimum compression is 10 bar, then the other 3 need to be well within 10% of that. The difference between 13 bar and 10 bar is 25% !!! That will cause problems. What does a current clamp on starter current reveal ?

Also I agree with Steeve, do the Manifold & Crankcase pressures together with all 4 spark plugs in the car with some sort of cylinder ID, Primary Ignition ?

Then the In cylinder wave forms separately.
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Re: Intake pressure waveform issue

Postby victor2k » Fri Oct 28, 2016 3:46 am

Hello,
Here is a new capture with the CAM/CRANK signals for reference and all spark plugs on engine
I think the angular velocity of crankshaft isn't constant through 720*(intake from cyl 1 is in the same time with compression from cyl2 (with a higher compression) :?:
One more question:why the crankcase pression coresponding to the cyl1 power stroke is lower than other?I have loss of compression at the exhaust valve seat?Image for this is attached.
Thank you
Attachments
Doc1.doc
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Toyota_Avensis_2004_20161028-0002.psdata
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Last edited by victor2k on Sat Oct 29, 2016 6:36 am, edited 1 time in total.
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Re: Intake pressure waveform issue

Postby steevegt » Fri Oct 28, 2016 2:06 pm

Using your crank signal, we can see that the speed of the engine is not the same between cylinders.
The engine speed differences, the intake pressure pulses, and the crank pulses, they can all be explained by the low compression in cylinder number 1.

The cause of the low compression is something that I believe we can't detect from the captures you had made. I can only see in there, from intake pressures pulses or crank pulses, that there may be some mechanical problem with the engine.
I don't believe we can say that this is intake valve related, exhaust valve related or piston related, just based on what you have given.
If someone can see more than that please fix my words... I only gave a quick look.

The problematic cylinder, should be the number 1, using your compression values, but because you didn't put a synchronization channel in the captures we can't say witch pulse is what cylinder.
We can use the cam signal for that, true, but before that I need to find a good waveform of that engine with some sync signal and the cam signal at the same time.

Maybe you should do a running compression waveform in cylinder number 1, instead of cranking compression. Or you can do 4 running compression waveform captures, and test all cylinders.
With that you may end up with information that may be conclusive, regarding intake or exhaust valves. You can also test the engine timing with that.

The low compression on number 1 could also be from a washed cylinder. Maybe, trying to do a new compression test with oil in the cylinder may rule that out.

PS:
I needed to use the freq math function for this crank signal. The crank math function doesn't work very well in your capture. This is something that I have notice before in some captures I had made. Not really a major bug, but at least we can say that the crank math function is not very robust. Or, I'm doing something wrong...
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