I just changed my sparkplugs today and when I got to the number 4 cylinder spark plug I pulled it out and it was covered in oil. I'm going to do a compression test I just have to get hold of the gauge later. So my question is does anyone know what the factory specs are when doing a compression test? I'm not going to jump to conclusions and say that my #4 piston blew, I just want to get this fixed. Thanks in advance for info.

 

Here's what GMDealerworld says about compression. It looks like it should be between 100-142 PSI. Or something like that.


Engine Compression Test
Perform the following steps to conduct a compression test.

Conduct the following steps to check cylinder compression.
1.1. Engine should be at room temperature.

1.2. Disconnect wiring from the ignition module.

1.3. Remove the spark plugs.

1.4. Throttle body valve should be wide open.

1.5. Battery should be at or near full charge.

For each cylinder, crank engine through 4 compression strokes.
The lowest reading cylinder should not be less than 70 percent of the highest.
No cylinder reading should be less than 689 kPa (100 psi).
Important: The results of a compression test will fall into the following categories:

• Normal -- Compression builds up quickly and evenly to specified compression on each cylinder.

• Piston rings -- Compression is low on the first stroke, tends to build up on following strokes, but does not reach normal. Compression improves considerably with the addition of oil.

• Valves -- Compression is low on the first stroke, does not tend to build up on the following strokes, and does not improve much with the addition of oil. Use approximately 3 squirts from a plunger-type oiler.

 

i had that problem with my eclipse, turned out to be a blown head gasket

 

yea usually thats not good

 

i dont think its the piston.

 

are you sure that the oil is coming from the combustion chamber and not seeping through the valve cover gasket? Did you look in the spark plug tube before you pulled the plug to make sure there wasn't any oil in it?

 

yes there was already oil in the spark plug tube. I tried to get a compression tester but it looks like i'll have to wait till tomorrow.

 

I'd bet it's just a bad gasket ring around the tube on the valve cover. When you pulled the plug oil from the tube got on it when you were pulling it out.

Do the compression test anyway just to be sure. There's enough problems with the #4 cyl on the ss/sc to warrant it. But I doubt it's anything serious.

Also you can rent a compression tester from autozone or something. Just make sure you look at it to make sure the needle is pointing at 0 before you use it. If the engine actually fires up while the compression tester is on it then it'll ruin the compression tester. I usually just pull the fuel pump relay and let the fuel out of the system to keep it from starting up.

 

I got to thinking about it and I think its the valve cover gasket to but i'm still going to do the compression test. I've already done one before at school so I know how to do it. I went to autozone and the advanced auto around here and neither of them have one I could rent out. I'll just wait and do it friday.

 

whatever works. Like I said, it's probably not that big of a problem. Especially if you're not getting a misfire code.

 

You should hear it in the idle if you cracked a piston ring, a misfire on a 4 cyl is usually pretty evident. If you see oil on the plug before you removed it, its not coming from inside the engine.

 

^^I got a misfire code last week but It didn't set off the CEL.
https://www.cobaltss.net/forums/problems-service-maintenance-69/many-dtcs-no-cel-76660/

 

Ouch, there's a bad sign.

 

you got a pending misfire code? On cyl #4?

 

I got P0300 misfire code. I believe its a random misfire code.

 

yea it's a random misfire. If you haven't thrown a cel then basically what's happening is your car is failing for a random misfire, but it passes on future cycles. So it creates a pending code and doesn't light the cel. If it fails for consecutive cycles then it'll light the cel.

How many miles are on your car?

I see you have a 2.7 pulley on your car. what kind of tuning is done?

 

29,000

 

I can pretty much safely tell you that all your problems are caused by your mods.

the P0172 is more than likely because of your 60#s and the fuel table settings you're using. Not saying its a problem, just that's why it's there.

The P0136 and P0140 says you have a bad O2 sensor. Downstream. Either that or your tuning has it set at a specific point and it isn't fluctuating, so it throws a code. But it's not constant so it doesn't throw a hard code. Also not a problem. It's just there.

The MAP problem sounds like you have an intake leak or a vaccum leak. But that could also be tuning related.

As far as the P0300 goes, it seems to me that it's pretty common for modified ss/sc to get pending random misfires. As long as it doesn't throw a hard code, I wouldn't worry about it.

I would just change out your valve cover gasket to stop that oil from leaking into the #4 plug tube. I don't know why you were replacing your plugs with 29000 miles... but I'm sure you have your reasons.

 

^^I know that my tune is messed up right now and i've been trying to get it retuned but schedule conflicts makes it really hard to do so. I'm going to do the compression test anyways probably friday and go ahead and change the valve cover gasket. Anyone know how much a valve cover gasket will cost?

 

probly 10-20 bux. depends on where you get it. Just make sure you tq the valve cover down right when you replace it.

 

Do you know what the torque specs are?

 

Torque specs on the valve cover are very very light believe me... if you try to tighten it down you will snap a bolt (did that). Get a small ratchet and get it hand tight... that's all.

That part of the engine isn't under pressure... so the cover just needs to be snug.

The number of bolts that hold the cover down are what's providing the force... so they don't need to be very tight. Also... make sure to keep the injector wiring harness (under the fuel rail) out of the way when putting the cover back on or you could pinch a wire which causes other problems (did that too).

 

Why would you need a new valve cover gasket? They are reusable, they are rubber and built into the valve cover.

 

Because its leaking.

 

i pulled my plugs today i have 37000 km pontiac pursuit gt and i have intake and exhaust done, but i have oil on the inside of my plugs. Im kinda worried. I also havent gotten any cel, but im curious if maybe i could be catching something on its way of going wrong?