spec for compression readings

[ez996]

Hallo everyone

I'm new to this forum. I have been a member for only a couple of days. I'm not Porsche owner yet. Perhaps I will become one by Monday. I have been looking for 993, it is my favorite body style. But last week I have stumbled on 99 996 C2.

Since I have never driven 996 before, I was actually surprised the way it felt and I like it :rolleyes: Engine has no oil leaks from rear main, it is dry. Plastic spark plug sleeves leak a little around o-rings but that is not a big deal I think. What I'm concerned is a little vibration from engine when it idles. There are no codes in the DME other than P0446 (emission code). No misfire codes. No pending codes. I researched 996 engine on the web and this forum so I know engine has design problem . I'm ok with that. Eventually I will have to replace it with new or rebuild unit as my goal with this car will be PCA track events. I just can't do it right after I buy this car (wife would killed me :help: ).

So my question is what would be a spec for compression test readings on 3.4 engine? As I'm planning to do compression test before I purchase this car Thank you :notworthy:

[slbates]

Hallo everyone

I'm new to this forum. I have been a member for only a couple of days. I'm not Porsche owner yet. Perhaps I will become one by Monday. I have been looking for 993, it is my favorite body style. But last week I have stumbled on 99 996 C2.

Since I have never driven 996 before, I was actually surprised the way it felt and I like it :rolleyes: Engine has no oil leaks from rear main, it is dry. Plastic spark plug sleeves leak a little around o-rings but that is not a big deal I think. What I'm concerned is a little vibration from engine when it idles. There are no codes in the DME other than P0446 (emission code). No misfire codes. No pending codes. I researched 996 engine on the web and this forum so I know engine has design problem . I'm ok with that. Eventually I will have to replace it with new or rebuild unit as my goal with this car will be PCA track events. I just can't do it right after I buy this car (wife would killed me :help: ).

So my question is what would be a spec for compression test readings on 3.4 engine? As I'm planning to do compression test before I purchase this car Thank you :notworthy:

I can't tell you what the spec is supposed to be but I can tell you what a 92k mile motor that was running very strong postedresults were.

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compression 160 psi on all cylinders

• 
  

All cylinders were at 98% per the leakdown

[ez996]

Thank you slbates for your response.

I did performed compression test (cold engine).

1 cyl 160psi

2 cyl 155psi

3 cyl 160psi

4 cyl 160psi

5 cyl 150psi

6 cyl 160psi

So all are within 10% range that is not so bad.

I also smoke tested intake system for vacuum leaks, and found problem with o-rings around plastic tubes- sleeves on few cylinders.

But don't know how big of an efect that would have on engine running.

I did remove oil cap and engine started to run realy bad so perhaps, new o-rings would improve a situation. Seems to me like engine crank case develops a lot of vacuum more than normal.

We had problem like this on BMW m62 engines and that was simply bad PCV plate in the back of the intake. But number 2cyl and 5cyl are for sure weaker and from what I understand those two cylinders almost always cause a problem when engine fails. I like the car alot though - color is ocean blue metalic.

I have to think about this one and do a little more reserch. My time will be up on Monday to let them know if I will take it or not.

[CosmosC4S]

When I did mine, the results were as follows:

#1 - 270

#2 - 265

#3 - 265

#4 - 255

#5 - 255

#6 - 255

I don't know why my numbers are way higher, perhaps due to the 3.6L engine?

But I know my mechanic told me they were solid results, and that the %difference is what matters most.

Oh...and I think you are not supposed to remove the oil filler cap with the engine running...

Edited July 22, 2007 by CosmosC4S