Oil in the Intake!

[coryatver]

My car is missing at idle and started to get really bad gas milege so I checked out to see if the air filter was bad and it had oil on it so i took off the intake and found more oil in the intake tube. Whats wrong? Where is this oil coming from?

[RednBlack]

Blowby, sry

[jmgtp]

I wouldn't jump to conclusions and say it's blowby.

That said, my reccomendation is to replace the PCV (positive crankcase valve) and inspect the rest of the PCV system. I had the almost the exact problem you described. The PCV was inoperative (clogged I assume) and engine vacuum drew small amounts of oil from the valve cover line that settled in the intake tube and TB when I shut the car off (even leaked down into my air filter which is an oil impregnated cone filter... when I noticed it was dripping oil I knew that it was coming from the pcv since I had not oiled the filter in quite a while). On start up there was enough residual oil in the intake tube and throttle body to make a large puff of blue smoke for a few seconds - then no smoke for the rest of the time I drove. I assumed the valve guides were gone until I had the intake off and opened the throttlebody up and saw the oil leak out. I replaced the PCV and the problem was instantly solved.

[coryatver]

The oil is definetly coming from the hose that plugs into the intake. I got a new PCV valve and put it on and a new filter and the thing still idles rough and misses. After putting the valve on i drove it for a few miles and pulled off the intake and it had a little oil in it again but maybe it was just the rest of the oil working out from before i don't know. I checked and it is running on all cylinders. It runs great on the road but still has a rough idle

[jmgtp]

Well sounds like the PCV was the problem. There is still probably a lot of oily residue in the intake. Go to your GM dealer and grab a can of top end cleaner (non aerosol) it will clean it out good. (You may also want to remove the rubber intake tube and air box and wash them clean). I think the instructions for running the can through the engine is on the site somewhere. I suppose that the plugs possibly may have fouled out. Pull them and check their condition. A can of GM top end cleaner in the gas tank at your next fill up couldnt hurt either.

good luck

[coryatver]

The car still has a bad miss at idle I can't figure it out. Also it will shutter sometimes when going down the road under light throttle in 4th gear. It has been this way for a while now. When it starts to shutter i just let off the gas and get back on it and it goes away. I thought it was the tranny but maybe it is related to the miss?

[coryatver]

I went out and cleaned all the oil out of the intake and then went for a drive. I came back and there is oil in the intake again. I don't know what the heck is going on. And the thing is only getting 200 miles to a tank of gas. It runs great on the road just idles like crap and gets horrible gas milege. It smokes a little on startup but after that its fine. I just don't get it.

[RednBlack]

Check your compression. Then get back to us. I have a feeling that you have trashed a cylinder. Has the car ever overheated?

[coryatver]

It hasn't overheated that I know of. But I bought it with 107,000 on it so i don't know. What is "blowby?" is that bad valve seals? I will see if i can find someone i know with a compression tool and find out what im lookin at. I tested it to make sure it was running on all the cylinders, when i pulled off each plug cap the engine noise changed so that means it running on all of them right?

[Lyle's GTP]

Blow-by is bad rings, which is almost always combined with burning oil (constantly). Your valve seals are letting go, because you are smoking a little on start-up. This happens because as your car sits for a while oil leaks down the valve stem and accumulates at the base of the valve. When you start your that accumulated oil burns off in the first few seconds. This will not result in poor preformance though unless you have a substantial leak in you PCV system. Did you change your PCV valve? A bit of oil accumulation in the intake tube is normal on higher milage engines, so cleaning it out won't help much at all. This oil is caused by excess gas build-up in the PCV system, in your case it could be from a blown head gasket (because of the quantity of oil you speak of). You should check your compression.

Lyle

[coryatver]

Yeah i changed the PCV valve. I looked around for a leak and couldn't find one but there could be one. Oil seems to be blowing in from the vacuum hose that plugs into the airfilter tube right before the intake. And that line runs to and plugs in to the front valve cover. I haven't checked the compression yet.

[Lyle's GTP]

Check that and get back.

Lyle

[coryatver]

I checked the compression on what I think is a weak cylinder becuase I checked to see if it was running on all cylinders again and the one made the least noise when I popped off the cap. It was the cylinder on the front bank beside the oil fill hole. It gave a compression of 120. Then I went over to the next one and it gave a compression of 140. What is the compression sopposed to be?

[RednBlack]

130 is a good average. I have checked cylinders that had higher than normal compression due to the amount of oil that it was using. When you pulled your intake, was there an port on the head that was oil soaked? If it is just 1 cylinder, it should stand out.

[coryatver]

I haven't pulled my intake. The plug was wet on the cylinder with low compression and the other one was burned clean.