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chromius
05-25-2004, 08:32 PM
Hey, just wondering if anyone has had a carbon buildup problem, that could help me out....I ran a compression test this weekend, and all the cylinders are reading high, however they are consistent across all cylinders (which is good i guess)... Now I am assuming that the only thing that could cause high compression is carbon buildup in the cylinders....so is it normal for the compression to have raised equally on all the cylinders? Or does anyone have any other ideas?

Also if it is carbon buildup...does anyone have any good ways to clean it? short of pulling off the head and blasting it....

Thanks

Jordan
05-25-2004, 10:54 PM
What compression PSI did you have on each cylinder? Hot or cold engine? Helpful if you provide such info....

Skunk#1
05-26-2004, 01:25 AM
they should all come up about the same because the cylinders should all be burning or operating the same. one good way but will require some work is to take the cat off the car. run the engine with good throttle and poor atf in the intake. that will smoke the $hit out of your neiborhood but the inside of your combustion chamber will be like bling bling. i dont recommend this unless it is the only way, just remember you dont need a lot of atf, like a cup (8oz) should be more then enough. or just squirt some in the cylinders via spark plug hole, the most important thing is to disconnect the cat, because if you dont the smoke comming out of the car will plug it up.

this can cause hot spots (carbon) and cause detonation, dieseling, etc. the labor rate for taking the head off and replacing the gasket is only 7.3 hours, so it is not a bad job or hit in the wallet. and while you have it out you cvan get the stud kit bmw sells for the head and use those instead of bolts. anyway im outty 5000.

chromius
05-26-2004, 03:27 AM
Thanks for the info Skunk#1..Thats helpful.

The cylinders were aprox between 195-205 psi across all cylinders on a cold engine, and with throttle wide open....if this helps...and thanks again:)

Jordan
05-26-2004, 03:46 AM
That does seem really high... You should be 160-170 cold.

Do it again with the throttle plate in the default closed place.

chromius
05-26-2004, 04:12 AM
I think I tried it with the throttle plate closed, and I was getting some pretty wacky readings...like after 7 cranks 110psi, then try again and it would be 130psi...I figured it wasn't getting enough air inlet to fill the chamber...and thats why I was getting the odd readings...and I know on the old carburated engines the throttle butterfly had to be open to check compression, So I would assume it would be the same on a Fuel injected engine.

But maybe I will try it again...

Jordan
05-26-2004, 04:30 AM
Well either way, the "proper" way to test for compression is this:

warm up engine, shut off

unplug all 6 injectors, unplug the wire at the coil.

remove all 6 spark plugs.

thread in your compression tester to cylinder 1

crank the engine 5-8 times for a proper reading

look at the gauge, record the reading, and move onto 2 etc

felixthecat
05-26-2004, 04:48 AM
i was gonna say...you cant check compression at anything above cranking,you wont get a true reading.

chromius
05-26-2004, 01:09 PM
Jordan, thats pretty much what I did, aside from doing it with the engine hot....and those are the readings I got....

Felix, what do you mean..anything above cranking?

Skunk#1
05-26-2004, 07:19 PM
hey man you have to take the fuel pump relay out, that is why it is going to be higher than normal. the the air going into your engine has fuel in it. this will make a difference of about 5-25psi in your readings. forgot about that.

chromius
05-26-2004, 07:56 PM
Originally posted by Skunk#1
hey man you have to take the fuel pump relay out, that is why it is going to be higher than normal. the the air going into your engine has fuel in it. this will make a difference of about 5-25psi in your readings. forgot about that.

Yeah I did that....well the fuse anyway