Chevy Cobalt Forum banner

1 - 15 of 15 Posts

·
Registered
Joined
·
9 Posts
Discussion Starter #1
Hello everyone, I've got an '06 Cobalt with about 110,000 miles that has been relatively problem-free, until now. I hardly drive my car, but am diligent on regular oil changes and have been using Mobil 1 exclusively for years. Over the past few weeks I've noticed a stronger-than-normal exhaust gas smell coming through the vents during stops at red lights. I just explored further today and don't see any obvious leaks with the exhaust system, but when I took the oil cap off with the engine running at idle I could feel considerable pressure (and the exhaust smell) originating from the oil filler cap! I'm hesitant to take it into a shop and get raked over the coals for an engine rebuild. I don't hear anything abnormal, the oil looks great with no signs of antifreeze mixing in, and the coolant reservoir is also normal. I wonder if it's as simple as a bad PCV valve, but I know that's probably wishful thinking. Anyone had this happen yet, know what it is, or know of an "easy" fix? Thanks.
 

·
Registered
Joined
·
330 Posts
It is fairly common to have exhaust like smell from the oil cap. Excessive blow by is another thing though.

Easy trick is to get a small square of paper and hold it against the oil dip stick. It it is easily blown off, you can determine you’ve got a lot of blow by. The paper should almost flutter, as vacuum will draw the paper to the dipstick. That is what should happen on a normally running engine. Otherwise you’ve probably got bad piston rings, bad head gasket. Something to that effect. Likely rings. Unfortunately these cars are prone to this, even with diligent care.

Im assuming you’ve removed the oil cap with the engine running? If so yes oil and blow by may come out. It usually does on most engines. Some more than others.

As far as an easy fix if this is true, no. Absolutely no easy fixes. The only thing you can do is run a thicker oil. Possibly a quart of Lucas. I have been doing that the last oil change and it’s slowed my oil consumption on my ‘06 Cobalt.

I had used a product years back called Restore. It’s an oil additive that claims to restore lost compression. It used to be advertised on tv a lot. You shake the product before opening and adding it into the oil. Obviously you don’t want to overfill the oil, so doing so at an oil change is ideal. If the oil is being consumed by the engine, you may add it when it’s about a quart under full. Anyways, I had a Datsun 280Z that had started to smoke and lost compression on two cylinders. I got the cylinders that were weak to go from about 90-110 psi up to 140-150 psi. That was according to a compression tester, not just guessing. Maybe that’ll work for you, it can’t hurt at this point if you’ve got worn rings. Stuff can be bought at Walmart. I also think the stuff works to help oil leaks a bit also. Not only did that car smoke a bit, but also had a rear main seal leaking. The seal leaked less afterwards, but eventually failed to where it always leaked. Sorry to say the car is rusted out now. Not a surprise being a Nissan, or Datsun, of the ‘70s.

Other things can cause exhaust to smell heavily of unburned fuel. Bad spark plugs can, usually won’t unless one is no longer firing. Usually it’ll be obvious because of a misfire. Another thing that comes to mind is a bad fuel injector. Not uncommon to go bad on an older car, especially with higher mileage. That will create a fuel smell at idle that is very noticeable. If left like that can cause internal engine damage and also ruin the catalyst converter.
 

·
Registered
Joined
·
14 Posts
This cobalt does not have a PCV valve is your oil running low after two or 3000 miles and having to add a quart if so I second Lucas oil I had a main seal leaking and used Lucas at oil change in and it helped the problem


Sent from my iPhone using Tapatalk
 

·
Registered
Joined
·
9 Posts
Discussion Starter #4
It is fairly common to have exhaust like smell from the oil cap. Excessive blow by is another thing though.

Easy trick is to get a small square of paper and hold it against the oil dip stick. It it is easily blown off, you can determine you’ve got a lot of blow by. The paper should almost flutter, as vacuum will draw the paper to the dipstick. That is what should happen on a normally running engine. Otherwise you’ve probably got bad piston rings, bad head gasket. Something to that effect. Likely rings. Unfortunately these cars are prone to this, even with diligent care.

Im assuming you’ve removed the oil cap with the engine running? If so yes oil and blow by may come out. It usually does on most engines. Some more than others.

As far as an easy fix if this is true, no. Absolutely no easy fixes. The only thing you can do is run a thicker oil. Possibly a quart of Lucas. I have been doing that the last oil change and it’s slowed my oil consumption on my ‘06 Cobalt.

I had used a product years back called Restore. It’s an oil additive that claims to restore lost compression. It used to be advertised on tv a lot. You shake the product before opening and adding it into the oil. Obviously you don’t want to overfill the oil, so doing so at an oil change is ideal. If the oil is being consumed by the engine, you may add it when it’s about a quart under full. Anyways, I had a Datsun 280Z that had started to smoke and lost compression on two cylinders. I got the cylinders that were weak to go from about 90-110 psi up to 140-150 psi. That was according to a compression tester, not just guessing. Maybe that’ll work for you, it can’t hurt at this point if you’ve got worn rings. Stuff can be bought at Walmart. I also think the stuff works to help oil leaks a bit also. Not only did that car smoke a bit, but also had a rear main seal leaking. The seal leaked less afterwards, but eventually failed to where it always leaked. Sorry to say the car is rusted out now. Not a surprise being a Nissan, or Datsun, of the ‘70s.

Other things can cause exhaust to smell heavily of unburned fuel. Bad spark plugs can, usually won’t unless one is no longer firing. Usually it’ll be obvious because of a misfire. Another thing that comes to mind is a bad fuel injector. Not uncommon to go bad on an older car, especially with higher mileage. That will create a fuel smell at idle that is very noticeable. If left like that can cause internal engine damage and also ruin the catalyst converter.
Thanks, I did the paper test and took a video here:
Paper test video

Strangely, nothing unusual at the oil dipstick location, just a lot of pressure from the filler cap. The oil is full (maybe sightly overfilled, but not by much if at all). What do you make of that, or my next steps in troubleshooting? If the oil is sightly over filled would that cause this?
 

·
Registered
Joined
·
9 Posts
Discussion Starter #5
This cobalt does not have a PCV valve is your oil running low after two or 3000 miles and having to add a quart if so I second Lucas oil I had a main seal leaking and used Lucas at oil change in and it helped the problem


Sent from my iPhone using Tapatalk
I don't notice any unusually high oil burn in this car, but then again I probably only drive 2,000 miles per year on it, if that.
 

·
Registered
Joined
·
9 Posts
Discussion Starter #6
Today I talked to a local mechanic and he said to try filling with premium and running the engine really hard for a bit to see if the seal can reseat itself. I also bought a bottle of Lucas for the next oil change, which unfortunately won't be for a while since I don't want to dump my fresh batch of Mobil 1 that went in a few weeks ago. Assuming the worst that I've got a bad seal and the additives don't work, is it reasonable to postpone an engine overhaul until the problem gets much worse? Or will this problem result in sudden engine failure, leaving me stranded somewhere?
 

·
Registered
Joined
·
508 Posts
Since you just Changed your Mobil full synthetic and put in 4 to 8 Oz of seafoam then take a long drive. A Good 1/2 tank long drive. Your Lucas oil treatment will work. 1/2 qt over full of oil will not hurt.
Short start & stop drives will not work as well a long drive is a must.
Then have your mechanic perform a compression check on all cylinders.
Have him log the pressure in all cylinders both DRY and with 1/2 to 1 Oz of oil.
Then share your numbers.
 

·
Registered
Joined
·
9 Posts
Discussion Starter #8
Since you just Changed your Mobil full synthetic and put in 4 to 8 Oz of seafoam then take a long drive. A Good 1/2 tank long drive. Your Lucas oil treatment will work. 1/2 qt over full of oil will not hurt.
Short start & stop drives will not work as well a long drive is a must.
Then have your mechanic perform a compression check on all cylinders.
Have him log the pressure in all cylinders both DRY and with 1/2 to 1 Oz of oil.
Then share your numbers.
Thanks, I have had the seafoam in this tank for a while as a stabilizer since I hardly put any miles on this car. My cobalt has been at the mechanic's since this morning for diagnosis/compression checks, and he actually called with an update before I saw your reply. He said the compression was excellent, but the spark plugs were very dirty. Said they think this amount of pressure/blow-by may be common in that 2.2L ecotech and didn't sound concerned at all.

I didn't see your post in time to ask about running the check dry and with the oil though. I'm picking up the car tomorrow so I'll ask how they did the test exactly, and what the log shows for each cylinder. I'm skeptical though, because I can smell a presence of exhaust through the vents at IDLE and stopped, that they couldn't detect. My theory is that there's so much positive pressure being generated that it's enough to leave the engine compartment and enter into the cabin air intake when the vehicle is stopped. (Like a clogged PCV in an engine that has one) But I'm not a mechanic, just someone that tries to be on my days off.

On a side note, I just bought a portable carbon monoxide detector for the extra peace of mind, and to see if I'm just imaging it.
 

·
Registered
Joined
·
2 Posts
19750
That the pcv valve for the cobalt LSJ 06 supercharger so yes they have one you have to take off your supercharger and intake manifolds to get to it
This cobalt does not have a PCV valve is your oil running low after two or 3000 miles and having to add a quart if so I second Lucas oil I had a main seal leaking and used Lucas at oil change in and it helped the problem


Sent from my iPhone using Tapatalk
 

·
Registered
Joined
·
2 Posts
This cobalt does not have a PCV valve is your oil running low after two or 3000 miles and having to add a quart if so I second Lucas oil I had a main seal leaking and used Lucas at oil change in and it helped the problem


Sent from my iPhone using Tapatalk
 

·
Registered
Joined
·
9 Posts
Discussion Starter #11
Since you just Changed your Mobil full synthetic and put in 4 to 8 Oz of seafoam then take a long drive. A Good 1/2 tank long drive. Your Lucas oil treatment will work. 1/2 qt over full of oil will not hurt.
Short start & stop drives will not work as well a long drive is a must.
Then have your mechanic perform a compression check on all cylinders.
Have him log the pressure in all cylinders both DRY and with 1/2 to 1 Oz of oil.
Then share your numbers.
All cylinders were above 145psi, dry. No misfires, no smoke in exhaust. I asked him to pull the "pcv hose" to see if it's clogged with a white sludge because I just read about that on a youtube comment with a similar issue. We'll see what they come up with, but something seems not right.
 

·
Registered
Joined
·
330 Posts
This engine hasn’t got a replaceable PCV valve. It’s got baffles in the valve cover to help keep oil from coming through, although the design sucks and oil comes right through into the intake manifold.

I wouldn’t be surprised if you did need new spark plugs. They need to be changed a little more often than usually on these cars sometimes. Especially if you’re experiencing oil consumption. That can make the car run rich and smell of fuel at the exhaust.

Over full oil could be a number of things. Either your or someone else has over filled the engine with oil at some point. Or it is getting fuel in the oil and is now over filled because of fuel. Fuel in the oil will be fairly obvious as the oil will smell heavily of fuel and be much thinner than regular oil.

I have noticed the oil will show over full on my 2.2 if the engine has sat for a bit. I usually start it for about 15-20 seconds. Turn it off. Then check the oil level. I noticed this when I’ve done an oil change, the recommended amount of oil over fills until the car is started and rechecked.

Also another thing you can experience fuel smell at the exhaust I forgot to mention is a bad fuel injector. If there’s an injector that’s not fully closing and letting fuel continually spray, it’ll smell a lot like fuel from the exhaust. Usually you’ll notice poor fuel mileage. This will also not be good for the internal parts of the engine. Mainly piston rings. Can cause oil consumption over time. And fuel in the oil as well.

Anyways. Spark plugs for these cars are cheap. I run the NGK 5019 G-Power platinum. Autozone still has them for cheap, $3.99 each. They used to sell for $3.49 each at O’Reillys but have since gone up to $5.99 each there.

Also, running one tank of premium fuel will not change much. I have only noticed a difference after using premium 93 models octane for at least a month or so. The only thing I gained was a lighter wallet really. Although the fuel mileage has risen slightly. I’m sure the valve seats are staying cleaner now, as advertised by Shell, which is all I use for fuel. Otherwise doing an induction cleaning will create the same effect. I did one when I first bought the car, it did make the fuel mileage go up. Although I also had to change plugs at the same time.
 

·
Registered
Joined
·
9 Posts
Discussion Starter #15
This engine hasn’t got a replaceable PCV valve. It’s got baffles in the valve cover to help keep oil from coming through, although the design sucks and oil comes right through into the intake manifold.
Thanks, do you know if the pcv ducting can be easily cleaned with a pipe cleaner from the pcv hose without removing the valve cover? My next plan is to pull the throttle body and clean out the intake, but if I can actually ensure the pcv system is completely unobstructed that would help.
 
1 - 15 of 15 Posts
Top