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1999 2.5RS
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Discussion Starter #1
I did a compression test today, after fearing the results for a while...
I loosened all the plugs slightly and the injectors and plug wires and did the test...
They all came out the same, (although at first, cylinder 4 was 20psi higher than the others, I think because the other spark plug on that bank was reallllllyyyy loose. I retested with the other plug on the same side reinstalled but not tight, and then got an equal number)
BUT I did not go WOT when I did the test. Is that ok? I read that its alright as long as they are all equal or close?
 

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GC8 FTW
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i;m lost...i thought when u did a comp test the entire spark plug was out..and all u did was crank the car
 

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Discussion Starter #5
right, but you have to loosen the other 3 spark plugs just slightly. On the one test where i got high numbers, the spark plug on the same bank was almost all the way out.
 

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Why do you need to loosen then other plugs? Just curious, I've never done that before. I've always just popped out the one for the cylinder I'm testing and went for it.
 

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Yup, all plugs out, car warm, WOT and crank for 3 - 5 revolutions. Can do with car cold but numbers will be lower. Numbers should be within 20% of each other.

I'm not sure on this and don't quote me but I've seen that 180psi is around 9.0:1 or 10.0:1 CR. I don't remember. You will only get that psi with a warm car. If you get it when the car is cold then you have a really tight engine.

[EDIT] Well all plugs in or out. I don't think it makes a difference. The cylinder should be sealed. I don't think one can interact with the other can they???
 

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GC8 FTW
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spshultz said:

[EDIT] Well all plugs in or out. I don't think it makes a difference. The cylinder should be sealed. I don't think one can interact with the other can they???
thats what i was thinking...each cylinder is its own...u could take all plugs out and test it...just try to put the plugs back in the same cylinder that they were in so that when u check your plugs the reading is accurate.....just what i remember from autoshop
 
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