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Possibly burning oil

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PurpleMystique

Hard-core CEG'er
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Nov 16, 2004
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Greater Des Moines Area
Well I think I might be burning oil. I changed it around 500 miles ago and put in 6.5 quarts of full synthetic, and at this point the dipstick is showing the level about halfway up the "safe" range. My exhaust tips get caked with residue pretty quickly, and there's even some on my back bumper. When I got the car it was suffering from a misfire in cylinder 3 and when I went to change the plugs I found a little bit of oil on two of them. Since then the misfire's been fine but now I'm getting a P1131. I changed the fuel filter in hopes that it would clear up, but if not I have a new O2 sensor waiting.
From what I've read, the burning oil could be piston rings, head gasket, or maybe cats? I did drive for a week or so on the misfire until I had time to get replacement plugs and install them, and I've heard that's not so good for the cats. How do I check for problems in each of those areas?
 
PurpleMystique said:
From what I've read, the burning oil could be piston rings, head gasket, or maybe cats? I did drive for a week or so on the misfire until I had time to get replacement plugs and install them, and I've heard that's not so good for the cats. How do I check for problems in each of those areas?
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You can check the engine for compression that should give you a rough estimate of the condition of the rings. Search for something like "Compression Test" For testing the pre-cats there have been plenty of posts that give instructions for removing the O2 sensors in a given order to test the amount of flow coming out of the bungs with the engine running. Search for "clogged precats" or something of that sort. If your head gasket was leaking it could mean you're burning oil, oil is getting into the antifreeze, or antifreeze getting into the oil, or you're just plain leaking oil. I haven't really heard of any of that happening with our engines though, supposedly the head gaskets are strong. That combined with the idea that these engines have an aluminum block with aluminum heads so they don't have the same heating/cooling problems with head gaskets as older cast engines with aluminum heads did.
 
Also, I just remembered a bad smell, possibly rotten egg-related. I went to check my oil after a ~20 minute drive and popped the hood. The guy riding with me smelled it right away. Would clogged precats cause oil to burn?
 
hi buddy i know u know what rings look like but ive tooken a pic of mine any ways these are the diamand racin pistons with the rings on there that are goin on my v6 block when my parts come in, but these are what u would need to change to stop the engine burning oil :)
 

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you could also be burning oil through the PCV valve. IDK if the V6 has an oil seperator but if so it might not be working properly. pull off one of the lines going from the PCV valve to the intake manifold and see if it is oily inside. if so you can add an oil seperator inline. also keep in mind that if you are burning oil it will be running rich (due to the oil in the cylinders). running rich will eventually melt down the cats which will give you a rotten egg smell.

do a compression test and if any cylinder is low (under 180PSI maybe. IDK what it should be for the V6) then do a cylinder leakdown test. this will tell you where your compression loss is. if the rings are bad (which is a suspect due to the oil burning) then you will hear air coming from the oil fill cap.
 
well the PCV valve wont stop the oil. thats the oil separators job. but if your gonna be in there it might not be a bad idea.

to build your own oil separator is like $20. you buy an air compressor filter from home depot, 2 X 1/4" NPT to 3/8" hose adapters, enough 3/8" fuel line hose to go from the PCV valve to the separator (wherever you decide to mount it) and back to the intake manifold. you basically replace the pipe that went from the PCV valve to the intake manifold.
 
You don't need an oil seperator. If the PCV valve is working properly you don't have enough flow to have a problem. Yes check or change the PCV valve. Also oil blowby will naot cause rich. The pcm will just back off the fuel mixture to compensate.
 
twocontours said:
You don't need an oil seperator. If the PCV valve is working properly you don't have enough flow to have a problem. Yes check or change the PCV valve.
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first off there is enough flow that IF the oil separator is not doing its job then it COULD suck oil into the intake. he needs to check and see if there is oil in the tubing going from the PCV valve to the intake manifold. if there is then he either needs to replace the factory oil separator or install another one.



Also oil blowby will not cause rich. The pcm will just back off the fuel mixture to compensate.
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only if the O2 sensor is working properly, which judging by what he stated earlier its not. because the sensor indicates lean its just gonna add even more fuel.

PurpleMystique said:
Since then the misfire's been fine but now I'm getting a P1131
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[FONT=arial,verdana,helvetica,sans-serif]P1131[/FONT][FONT=arial,verdana,helvetica,sans-serif]Lack of Upstream Heated Oxygen Sensor Switch - Sensor Indicates Lean - Bank No. 1.[/FONT]
so now it has the correct amount of fuel+oil from somewhere+extra fuel cause the PCM thinks its running lean. a car that is running Rich tends to have more blow-by. more blow-by means more crankcase pressure. increased crankcase pressure means more tendency of oil to get past the oil separator and into the in intake manifold.


start with replacing the bad sensor and looking in the line between the PCV valve and the intake manifold for oil. if there is no oil in the line then the oil almost has to be coming from the oil control rings. then do a compression check and a cylinder leak down test.
 
striker2 said:
start with replacing the bad sensor and looking in the line between the PCV valve and the intake manifold for oil. if there is no oil in the line then the oil almost has to be coming from the oil control rings. then do a compression check and a cylinder leak down test.
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I'll try and take car of this either tonight or this weekend, whenever I get time.

Dandan27 said:
How many miles do you have on this car?
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82,100, I've had it for 2,000 of those miles. The previous owner installed a custom exhaust and the clutch is already showing some wear, so I'm guessing he ran it fairly hard.
 
Okay, today taking an onramp with all 4 windows down I got a very strong rotten egg smell. I cleared the codes a couple days ago and the P1131 hasn't come back yet. Is the smell because I need to replace the O2 sensor or is it bad pre-cats?
 
pre-cats or cat most likely. its most likely to be bank 1 as thats the one that the code is for. sounds like its time to either gut the pre-cats or get a set of headers.
 
I did buy an O2 sensor from Advanced Auto to put in but when I looked at it it had the circular connector and I need the square one.
I replaced the fuel filter and I've gone a couple hundred miles without the O2 sensor coming back. I'm going to gut the precats asap and we'll see what happens.
 
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More Check engine light to come

More Check engine light to come

Sensor replacement is easier than precat gutting..Advance Auto should be able to provide a sensor that fits, they may have given you Downstream sensor you need Upstream. Check their web site. You will also get a CEL from precats no longer working. There is some workaround (MIL eliminator), I believe.
 
FavoriteMystaque said:
Sensor replacement is easier than precat gutting..Advance Auto should be able to provide a sensor that fits, they may have given you Downstream sensor you need Upstream. Check their web site. You will also get a CEL from precats no longer working. There is some workaround (MIL eliminator), I believe.
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It should have been the right part...even on their website it's listed as upstream for 1/2/99 on, a Bosch 15718.

So two questions:
1. Is there any danger to using the MIL eliminators? What if something really was wrong, but the CEL didn't tell me because the MILEs were faking it out?

2. Is it possible that replacing the sensor/gutting the precats will stop me from burning oil?
 
1: the only thing the MILs will prevent the CEL from coming on for is a malfunctioning CAT or rear O2. you can do the same thing in a tune by turning off the rear O2s

2: not likely.
 
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