The effects of adding Too Much Oil

[speedyx14]

94 V6 Firebird
Okay everyone. I've been a member here since I bought my Firebird back in July. I got the car for cheap as a project, and have found Your advice very helpful.
With your help I have fixed oil leaks, fuel pump issues etc. I am very close to having the car in prime running condition.
Along the way I have often made issues worse through my own ignorance. I consider this car as being my auto mechanic class.

The biggest mistake I made happened months ago when I had a rapid oil pressure sending unit leak and added oil much too liberally(about 3 quarts too much) which can be attributed to my ignorance. My car got some very bad side effects: Clouds of blue smoke in exhaust, black soot in exhaust, loss of power.

I have had the oil at the proper level for a couple of months now. The power has returned, but the car runs very rich. A half tank of gas will be gone within 10 miles of driving. I can idle the car for just 30 minutes and I can notice a loss of fuel on the gauge. I am so close to having this car on the Road but I aint gonna drive it running this rich.

I know a lot of things can go wrong when you overfill your oil, but the engine sounds good. I had a compression check and all cylinders hit 180 but one(170, but hit 180 after sprinkling some oil). I changed the Oxygen Sensors the other day and not much seems to have changed. Changed the Air filter(which was partially soaked in oil) Still runnin' rich. I Seafoamed the car and saw no improvement.

Do you guys think the black oil soot wiped out my cat converter?I thought it just might clear itself out. Is the engine done? Can it be brought back to it's previous performance? What can I do to get my mileage back? EGR? Cat? New Engine?
Please help. I'm gonna throw some new spark plugs in there soon, but I have a feeling it won't help because the excess oil should have burned off by now.

[FadeToBlak121]

Re: The effects of adding Too Much Oil

cat is prolly bad. do you have a ses light on? still though 10 miles on half a tank of gas is ridiculously bad, idk if a bad cat could make you get that bad of mileage.

[speedyx14]

Re: The effects of adding Too Much Oil

I got the check engine light on when the incident first happened. But I don't get anything now. Maybe I exaggerated when I said 10 miles on half a tank because I haven't really measured it(although I wouldn't be surprised). A lot of what I notice is from the car idling. Say I let it Idle an hour, I might me down nearly a quarter tank. I originally thought the oil would just burn itself out of the Cat.But maybe that soot is still stuck in there causing back pressure.

[FadeToBlak121]

Re: The effects of adding Too Much Oil

a clogged cat generally stays clogged. not saying that is the only problem but that seems pretty likely.

[cam98aro]

Re: The effects of adding Too Much Oil

i dont see how your car would run if it was using 7+ gallons of gas in 10 miles

[flamingchicken]

Re: The effects of adding Too Much Oil

i dont see how your car would run if it was using 7+ gallons of gas in 10 miles

thats like filling the combustion chamber halfway with gas, and thats called hydro-lock. cant compress a liquid.

but honestly, get some realistic numbers. my cat clogged up once and i had no power, at all. i had to pull over on the interstate and pry the caseing open to get some flow. you would notice a difference in power if your cat was clogged.

[nascar24jd]

Re: The effects of adding Too Much Oil

If it is drivable, you need to drive it and calculate the actual mileage that you are getting. There is no way that it can be using 1/4 tank of gas by idling for 1 hour unless it is leaking.

Are there any fuel leaks?

[speedyx14]

Re: The effects of adding Too Much Oil

If it is just past 1/4 mark and I let it idle for 30 minutes, I will notice it a bit under the 1/4 mark. I will lose 1/4 of a tank within 10 miles of driving. I will Test the car with more gas very soon, but all I know is that that oil crapped something out big time and my mileage is screwed.It can't be a fuel leak because the mileage was fine until I overfilled the engine. I am seriously starting to think that it may be the cat. If I had all that oil soot visibly in my tail pipe, I can only imagine how much got into the cat.

[ssms5411]

Re: The effects of adding Too Much Oil

Change your oil and put 4.5 quarts in, check the fuel filter to mke sure there are no leaks coming from it. The gauges for the fuel , I know on mine will stay around the 3/4 mark for along time then it will start to go down fast. I know they are not correct, I wait until it gets to almost gets to the 1/4 mark then fill up. Takes around 13.5 gallons when I do this. So just keep track of how many miles per gallon your using.

[Mr. Logger]

Re: The effects of adding Too Much Oil

Perhaps the O2 sensors were fouled so much they call for too much fuel... Just a thought

[Mogobs30th]

Re: The effects of adding Too Much Oil

Mileage of the car would help, but I can't honestly see how the engine is burning thru gas that fast. If you're getting less than 12 mpg city driving, then the car probably wouldn't be running in the first place. And no codes?

[speedyx14]

Re: The effects of adding Too Much Oil

94 is OBD1. I got engine/gauges light during the overfill, but have since reset the computer and never checked them.

[tkoforpresident]

Re: The effects of adding Too Much Oil

ok bud, first of all check those codes, the computer stores them so you can see what may be wrong.

secondly (after you've checked out the codes) i'd replace the cat converter and both o2 sensors, both are possibly shot and they're not that expensive to replace ( 20$ per o2 sensor and 50$ for a catco cat converter)

[Teal3800]

Re: The effects of adding Too Much Oil

If it is just past 1/4 mark and I let it idle for 30 minutes, I will notice it a bit under the 1/4 mark. I will lose 1/4 of a tank within 10 miles of driving. I will Test the car with more gas very soon, but all I know is that that oil crapped something out big time and my mileage is screwed.It can't be a fuel leak because the mileage was fine until I overfilled the engine. I am seriously starting to think that it may be the cat. If I had all that oil soot visibly in my tail pipe, I can only imagine how much got into the cat.

If you are gaugeing your potential mileage on the last 1/4 tank of gas, you can't do it that way with these cars at all. I used to get an average of 600 km to a tank, roughly 36mpg in my 97 that I used to own and in my 96 before my cam , I'd get about 450 on the top half, 150 to the 1/4 mark then I'd fill up because I'd be very lucky to get 50 out of the bottom. From what I have read the tank is triangle shaped and our gas gauges are far from accurate. Put a full tank of gas in it and drive it.

I'd still replace the cat also since it probably is toast.

[tkoforpresident]

Re: The effects of adding Too Much Oil

If you are gaugeing your potential mileage on the last 1/4 tank of gas, you can't do it that way with these cars at all. I used to get an average of 600 km to a tank, roughly 36mpg in my 97 that I used to own and in my 96 before my cam , I'd get about 450 on the top half, 150 to the 1/4 mark then I'd fill up because I'd be very lucky to get 50 out of the bottom. From what I have read the tank is triangle shaped and our gas gauges are far from accurate. Put a full tank of gas in it and drive it.

I'd still replace the cat also since it probably is toast.

yeah my fuel gauge stays all the way at the full mark for the first 6 or 7 gallons before it starts to plummet like a stone in a pond.