Jon Dahl

Last month I started this thread here: https://classicoldsmobile.com/forums...-question.html

I was having issues with the engine shaking while running. I thought it was the catalytic converter... So, I cut it off and replaced it with a straight pipe.
Still shakes.

I checked the sensors on the intake last night, and they still look fairly new. My father drove the hell out of that car and because of this replaced much of the engine. I had replaced all the spark plugs last year and checked them last night. They seem to be fine and firing.

The oil has me a bit concerned though. It looks like river mud and has a quart too much in the pan. If anything it should be low. Oil doesn't magically appear. (And if it does, you can bet I'm selling the car to Opec and retiring).
The radiator is full of nice transparent green antifreeze, but the car is going through gasoline at an alarming rate. I assume the fuel is somehow getting into the pan.

I didn't want to have to get rid of my car. It was a nice daily driver for the last 5 years. Right now I'm having to drive my '57 around town, and it's not 100% itself. (It's very hard to stop).

Any ideas of what is causing this? (Other than the 300,000 miles)

Eric Anderson

Does the oil smell like gas? I've had a couple fuel leaks to the crank case and it seems to thin the oil out the river mud sounds more like water.

The radiator is still full but is the overflow bottle still full ? That could account for a quart of coolant.

Jon Dahl

Honestly, I'm not sure about the smell. I did try, but I was unable to determine if it was gasoline in the oil. I'm thinking about putting some in a small pan and seeing how fast it burns. While it looks like river mud, it flows like water. My sense of smell has obviously been damaged by years of changing the diapers of my three kids.

I didn't even think of the overflow on the radiator, yes, it is empty, but I've not noticed the tell-tail signs of burning antifreeze.

csstrux

Sounds like you have water in the oil. Have you been losing coolant? Bad head gasket maybe? Sounds like my toyota did when it blew a head gasket.

dan2286

I dont know how the older 3.8s are, but the newer ones love to go through intake gaskets.

Here is a pic of my grandpas car when his went. It was bad enough to hydro-lock the engine, it actually ran great after we changed the gasket and got the anti-freeze out of the cylinders.

025.jpg

Lady72nRob71

Mechanical engine-mounted fuel pumps have been known to leak fuel into the oil. My mom's 307 did this once. Oil looked clean, but it flowed like water and the level increased.

Your car looks to be EFI, with an electric fuel pump. Recon it is running EXTREMELY rich? Extra gas can soak in through the piston rings and the car would run like crap. If this was the case, the SES light should be on.
Fuel pressure regulator maybe??

Oil looking like sludge makes me wonder though. I would think coolant would be getting mixed in for it to turn THAT color...
If so, head or intake gaskets may be needed.

Oldskeeper

Hi Jon
I have a 93 olds 98 touring sedan with 120K and had a similar prob, the bucking action was the crank sensor behind the harmonic balancer and the intake gasket leaking antifreeze into the oil pan is common.If you were burning the antifreeze the check engine light would be on (o2 senser does't like antifreeze).

Jon Dahl

I put a new harmonic balancer on it a few years ago, but you may be right about the sensor. I let it idle for about five minutes about an hour ago and the "Low Coolant" light came on, it hadn't done that before, but none of the other lights did.
I assume it is antifreeze in the oil, but it sure doesn't look like it. No foam, clean plugs, and the oil doesn't seem to separate when left to sit, but the antifreeze is going somewhere. It's not burning it
I had a Monte Carlo that blew the intake gasket. It ate O2 sensors.

I thought it may have been one of the sensors on the intake because of the amount of gasoline the car is using. I could literally see the needle drop as I drove around for about ten minutes trying to figure this out. (It took about an eighth of a tank to go just a few miles).

It's the strangest thing when this began. I was on my way to work when I decided to stop and get a coffee. I let the car idle outside, and when I got back in, it wouldn't run worth a damn.
Once I got to 30 mph, it straightened out and stopped bouncing around.
Now, it doesn't matter how fast I go, it runs terrible.
Even though it's a 1991, it's still much newer than what I'm use to working on, or even have diagnostic tools for.

I'll keep tinkering with it, thanks for the ideas!

joe_padavano

This could be any number of things, but let's start with the easy ones first. It's likely that the injectors are gummed up. The best way to test for this is to pull the injectors and have them flow tested at a shop, but by the time you do that, you mightaswell just stick in new ones. You can try to have injector cleaner run through the injectors first (the equipment to do this enables it to be done on the engine, so no disassembly is required). Also consider cleaning the throttle body. The other highly likely cause is the ignition module and/or coil packs.