Help! Low Compression 1-3
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Joined: May 2006
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Help! Low Compression 1-3
Hi All,
99' A6 Avant 2.8. 98K miles
Car would not start and made a strange sound around the passenger side of the engine. checked compression and only have 30psi consistent accross cylinders 1, 2, and 3. Numbers 4, 5, and 6 are all strong and normal.
Did a timing belt hydraulic tensioner replacemet just to make sure I had prooper tension on the belt. Put it all back together and the same problem. No improvement.
- No start.
- Strange sound from passenger bank.
- Low compressio in cylinders 1-3.
Timing is perfect and is not an issue.
QUESTION: I'm guessing there is a problem with teh mechanical camshaft adjuster that could be throwing the timing off on the intake cam on the passenger side. My guess is that this could cause low compression numbers and the strange sound if the intake cam is opening valve out of time. Thoughts?
What do you all think? What do you think is wrong? Will my VAG COM tell anything for this MY?
I do not think this is a head gasket since all 3 cylinders of one bank are acting the same way at the same time. No oil/coolant mixing going on. Somthing is affecting this side of the engine.
Thanks and Kind Regards,
Joe.
99' A6 Avant 2.8. 98K miles
Car would not start and made a strange sound around the passenger side of the engine. checked compression and only have 30psi consistent accross cylinders 1, 2, and 3. Numbers 4, 5, and 6 are all strong and normal.
Did a timing belt hydraulic tensioner replacemet just to make sure I had prooper tension on the belt. Put it all back together and the same problem. No improvement.
- No start.
- Strange sound from passenger bank.
- Low compressio in cylinders 1-3.
Timing is perfect and is not an issue.
QUESTION: I'm guessing there is a problem with teh mechanical camshaft adjuster that could be throwing the timing off on the intake cam on the passenger side. My guess is that this could cause low compression numbers and the strange sound if the intake cam is opening valve out of time. Thoughts?
What do you all think? What do you think is wrong? Will my VAG COM tell anything for this MY?
I do not think this is a head gasket since all 3 cylinders of one bank are acting the same way at the same time. No oil/coolant mixing going on. Somthing is affecting this side of the engine.
Thanks and Kind Regards,
Joe.
Thread Starter
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Joined: May 2006
Posts: 7
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The timing belt is set correctly and is not the issue.
When the problem started, I thoguht it was a bad starter since the sound was similar. I checked for engine rotation and after I saw the serp belt rotating, I pulled the cover off the timing belt and saw that was ok.
After seeing the compression numbers on the passenger bank only, I thoguht perhaps I had a loose belt that perhaps had jumped a few teeth on the passenger side sprocket. Opened up the front of the engine and the timing was OK but the hydralic tensioner did appear to be weak.
Bought a new hydraulic tensioner from the dealer and refreshed my timing belt. The 2 cam sprokets are timed perfectly relative to each other. Factory timing belt replacement proceecure followed. Timing between crank and both exhuast cams is perfect and so is the belt tension. Not the issue here.
After it was all put back together, the funny starting sound was the same as before.
I suspect I have a problem with the intake cam timing on my passenger side. This could explain the noise and the lack fo compression on that one side of the engine. What is the experience out there on the adjuster failures for the chain between the exhuast and intake cams?
Thanks,
Joe.
When the problem started, I thoguht it was a bad starter since the sound was similar. I checked for engine rotation and after I saw the serp belt rotating, I pulled the cover off the timing belt and saw that was ok.
After seeing the compression numbers on the passenger bank only, I thoguht perhaps I had a loose belt that perhaps had jumped a few teeth on the passenger side sprocket. Opened up the front of the engine and the timing was OK but the hydralic tensioner did appear to be weak.
Bought a new hydraulic tensioner from the dealer and refreshed my timing belt. The 2 cam sprokets are timed perfectly relative to each other. Factory timing belt replacement proceecure followed. Timing between crank and both exhuast cams is perfect and so is the belt tension. Not the issue here.
After it was all put back together, the funny starting sound was the same as before.
I suspect I have a problem with the intake cam timing on my passenger side. This could explain the noise and the lack fo compression on that one side of the engine. What is the experience out there on the adjuster failures for the chain between the exhuast and intake cams?
Thanks,
Joe.
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OK - possible you flooded that bank of cylinders due to who knows what and now they are "washed" and therefor low compression.
Have you pulled the plugs (smell heavy of fuel?) let it sit overnight or longer opened up. Put in new plugs and try to start it again.
This is a *not uncommon issue for the 1.8T.... not sure on the 2.8 though.
Worth a shot however.
Have you pulled the plugs (smell heavy of fuel?) let it sit overnight or longer opened up. Put in new plugs and try to start it again.
This is a *not uncommon issue for the 1.8T.... not sure on the 2.8 though.
Worth a shot however.
Thread Starter
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As suspected, the problem is not some fuel flood situation. I cranked on the car for a good long time and it only tried to turn over once but never made it.
Checked the selenoid valve for the camshaft adjuster and it read the correct Ohm reading and the connector @ terminal 1 was outputing a voltage while cranking.
The hunt continues....
Checked the selenoid valve for the camshaft adjuster and it read the correct Ohm reading and the connector @ terminal 1 was outputing a voltage while cranking.
The hunt continues....
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OK. But if you're washing the cylinders with raw fuel from cranking - don't rule it out is all I'll say here. I've seen it many times over the years.... It can and does happen and seems just like a blown head.
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I have always disagreed with that hypothesis. I think it is an oil pressure issue. High pressure hyper extends the lifters. It used to happen on the late 1980's VW's too. I'm not buying the possibility that fuel can wash down the rings that drastically and that quickly.
Of course, I can't prove anything one way or the other.
Of course, I can't prove anything one way or the other.
Thread Starter
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Fuel - Car sat with no sparkplugs for more than a day before tyring to start it again. Any remaining fuel would have dissapated. Even with raw fuel washing down the cylinders, good rings and valve train should provide more compression than what I am seeing.
Oil Pressure & Lifters - Interesting thought, but I've not heard this before and have questions about how this could occur from a mechanical perspective. What's your theory on how this would play out?
Thanks,
Joe.
Oil Pressure & Lifters - Interesting thought, but I've not heard this before and have questions about how this could occur from a mechanical perspective. What's your theory on how this would play out?
Thanks,
Joe.