Polo 6N 1998 1,4 AKV-Engine Low Compression

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Polo 6N 1998 1,4 AKV-Engine Low Compression

Postby terbo » Sat Mar 26, 2016 7:25 pm

Hi,

Our VW Polo decided to run like crap from one day to the next.
Relative Compression did not look good.
Did a compression check with the WPS500 - doesn´t look good.
Tryed to test with the WPS500 at the Dipstick and Intake but could
not get any fitting that would seal.

Did a self made Leakdown test and i have some pressure at the Breather
Hose from the Crankcase :(

Is there anything else beside the Piston or Ring that could be the cause ?

The little dip after the Compression Peak is missing on Cylinder 2.
Does that support the Crankcase as cause ??

Maybe someone has a opion before i replace the Engine.
Car has about 100 000 km on the odo if it matters.
Greets Chris
Attachments
z1-1.psdata
Cylinder 1
(95.61 KiB) Downloaded 54 times
z2-1.psdata
Cylinder 2 - BAD
(80.17 KiB) Downloaded 46 times
z3-1.psdata
Cylinder 3
(95.91 KiB) Downloaded 42 times
z4-1.psdata
Cylinder 4
(97.21 KiB) Downloaded 38 times
rel2-polo.psdata
Relative Compression
(613.36 KiB) Downloaded 38 times
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Re: Polo 6N 1998 1,4 AKV-Engine Low Compression

Postby STC » Sat Mar 26, 2016 8:27 pm

Generally speaking, 100k km is not enough to kill this / any engine. May we make replacing the Engine a last resort ?

Autodata suggests that the Spec for compression is 7 - 15 bar (very helpful) Indeed we all know all 4 should be even.

Your compression leak has to be going Up, Down or Sideways.

First the compression test must be done with the throttle plate wide open, or removed from the car. Did you do that?
Next consider doing Dry & Wet Compression tests (adding a little oil into each cylinder prior to testing)

Don't underestimate the value of "Running Compressions" on Each Cylinder.

Oil Loss ??

Water Loss ??

Smoke at Tailpipe ?? What Colour ?? What does it smell of ?
Last edited by STC on Sun Mar 27, 2016 1:56 am, edited 2 times in total.
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Re: Polo 6N 1998 1,4 AKV-Engine Low Compression

Postby Liteace » Sat Mar 26, 2016 11:25 pm

STC wrote:Generally speaking, 100k km is not enough to kill this / any engine


It is if it's not been looked after properly, oil changes, quality of oil used, it might have had the nuts thrashed out of it for 25k with crap oil in
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Re: Polo 6N 1998 1,4 AKV-Engine Low Compression

Postby STC » Sun Mar 27, 2016 3:29 am

Liteace.

It is if it's not been looked after properly, oil changes, quality of oil used, it might have had the nuts thrashed out of it for 25k with crap oil in


With Opening Poster "Terbo" being a Seasoned Pico Owner / User. For that reason, I did omit to state the obvious basic stuff but offered further testing suggestions. Generally Speaking :D

My Apologies
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Re: Polo 6N 1998 1,4 AKV-Engine Low Compression

Postby Fat Freddy » Sun Mar 27, 2016 5:21 am

I think Liteace is on the money.
And it is possibly repairable. Compression isn't too bad. But low.

Is there anything else beside the Piston or Ring that could be the cause ?


Yes.

Running comp as suggested would be good.

HTH
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Re: Polo 6N 1998 1,4 AKV-Engine Low Compression

Postby terbo » Sun Mar 27, 2016 9:16 am

After a talk with my Sister who drives it mostly,
she said, it started at highspeed on the freeway, there was
a "hard jerk" and big POPP and then it through big smoke clouds
and started runing von 3 cylinders.

She had to put in about 1,5 Liter Oil between the happening and
the house (rest way was about 200km - so its burning about 0,7 Liter/100km)
because the oil warning came on twice on the way home and she filled up.

That really says to my that the air i feeled wasn´t just "normal wear" :(
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Re: Polo 6N 1998 1,4 AKV-Engine Low Compression

Postby volrem » Sun Mar 27, 2016 10:15 am

Probably it's cheaper to install new (used new) engine.


But I would still do some more measurements just because it's good case to study from.

I would like to see WPS on crankcase along with cylinder sync and crank sensor (engine running). And same thing but WPS in #2 cylinder (running compression).
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Re: Polo 6N 1998 1,4 AKV-Engine Low Compression

Postby terbo » Sun Mar 27, 2016 1:20 pm

Hi,

Yes, thats the Plan - organized a used Engine today and started
ripping the old Engine out.Just a 1,4l - 2 Hours and its out...

I did some running Compressions before i started just for kicks
and because someone asked.Sorry, but now the Engine is out
besides 3 Bolts of the Engine Mounts....Everythings off already.

Maybe something usefull in the running compressions....

Greets
Chris
Attachments
z4run2.psdata
Cylinder 4 Idle - lower Scale
(575.96 KiB) Downloaded 31 times
z4run1.psdata
Cylinder 4 Idle
(501.22 KiB) Downloaded 26 times
z3run.psdata
Cylinder 3 Idle
(500.74 KiB) Downloaded 30 times
z2run3.psdata
Cylinder 2 Idle - lower scale
(546.7 KiB) Downloaded 29 times
z2run1.psdata
Cylinder 2 Idle
(485.34 KiB) Downloaded 34 times
z1-run.psdata
Cylinder 1 Idle
(497.32 KiB) Downloaded 35 times
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Re: Polo 6N 1998 1,4 AKV-Engine Low Compression

Postby tode » Sun Mar 27, 2016 8:46 pm

If the test with WPS sensor in the intake manifold has given negative results, the problem of your car is a relief valve damage, from Z2-1 file it is clear that the lack of exhaust bag because the pressure rises quickly, a test, confirming, my idea is a test with 500 WPS in the exhaust pipe.
Attachments
bad waveform.jpg
Bad waveform, for me the exhaust valve doesn' t close.
good waveform.jpg
Good waveform
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Re: Polo 6N 1998 1,4 AKV-Engine Low Compression

Postby Fat Freddy » Mon Mar 28, 2016 12:10 am

My wild stab is a problem with the inlet valve of #2.

Cylinder pressure goes way below inlet manifold. No air entering engine.

Nothing to compress, so low compression.

High cylinder vacuum drawing oil into the cylinder and pumping it out.

But Hey! Chuck an engine in.


HTH
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