runs rich, gas in oil

Hi,

1993 Chevy S10 Blazer 4.3L Vortec 4x4 auto, @191K mileage.

It has been running extremely rich and throttle even in neutral sounds sluggish like it is clogged and having trouble clearing out. If I mash the gas, it accelerates rough, but then clears up and runs smooth. Slowing down and the throttle response repeats itself almost like it is drowning itself. If I drive it up the road, it is very sluggish and feels as it is being held back until the speed increases and the throttle smooths out again. This happens continuously. Blue smoke out tailpipe and choking fumes and eye burning too. Black spots from rich exhaust also on grass.

My scanner Actron code reader said code for HO2 sensor rich. I replaced with a new HO2 sensor, started it and it ran no different. I reread any codes and this time I got the opposite saying HO2 sensor lean. It feels like it get's good pressure out the tailpipe so i don't think it is cat converter related. I dropped the oil and it overflowed out of my container there was so much gas in the oil. Not good for the engine. It's been a week or two of running it very sparingly and the oil looks overfilled again.

I've changed parts over the past few years like fuel pressure regulator, MAP sensor, EGR sensor, plugs, wires, cap n rotor, fuel filter a few years ago. I'm going to redo the fuel filter because it's good maintenance and I can rule that out. About 2 years ago I did have to open the intake plenum because a plug/hose came off one of the injectors and it was leaking in. I plan to open it again and recheck everything. Can anyone share any ideas or similar occurrences they've had with these older S10 Blazers?

Thank you.

Check fuel pressure real close.
Check for proper pressure and or fast leak down.
Any engine miss fires or cylinders missing.
How are plugs and wires?
Other things can be TPS or map coolant and air tempt sensors to computer and MAF sensor if it has one.
Needs put on a engine capable scanner and read out all sensor data.

And also check for restricted exhaust system.
What is engine vacuum at idle and at 2K rpm?

Check fuel pressure real close.
Check for proper pressure and or fast leak down.
Any engine miss fires or cylinders missing.
How are plugs and wires?
Other things can be TPS or map coolant and air tempt sensors to computer and MAF sensor if it has one.
Needs put on a engine capable scanner and read out all sensor data.

And also check for restricted exhaust system.
What is engine vacuum at idle and at 2K rpm?

I rang a bell with myself after posting this thread. Maybe it is related to something coming loose again under the plenim. It happened before, so I need to check that again. I'll start with this and post an update sometime later in the week. Thanks for the response MT. I'm just wishing I had the MT-2500 too. :-)

Gas in the oil is a classic plenum leak. Either the nut kit, regulator or the spider assembly.

Just as I suspected, there was a puddle of gas sitting under the plenim. Standing in front of the Blazer looking in at the plenim, the gas was accumulated on the right side rear. I pulled all the injector plugs and made sure they were good, dryed the puddle and checked the plug/wires in center on backside of pressure regulator. The pressure regulator I just replaced about a year or so ago so that should be good.

The two plastic fuel hoses that go from the center plug to the right rear of the plenim looked good to me, but the inner one made me second guess because that's where all the fuel was. After drying it out in there, I turned the key on KOEO to see if fuel would flow, but it didn't. I forget what I was told before about starting it with the plenim off, don't think you can do that safely. So, if it is a leaky plastic line, they are about 1/2 inch diameter and maybe 6 inches long, how can I actively verify this?

Do not hit that start button.
Just jumper fuel pump or.
Just turn key on a couple of times and let pressure build up and watch for leaks.

Do not hit that start button.
Just jumper fuel pump or.
Just turn key on a couple of times and let pressure build up and watch for leaks.

Ah, I only turned the ignition on once. I'll try cycling it. After looking up what a nut kit was, fuel line nut kit, I am now suspecting that this little assembly might be the culprit. I just wanted to verify it first by checking like you said. But if that doesn't work, then I may just replace it anyway. I am getting very close to the fix. This probably was the original culprit from a year or so ago too, but I didn't realize it. Thanks.

Ah, I only turned the ignition on once. I'll try cycling it. After looking up what a nut kit was, fuel line nut kit, I am now suspecting that this little assembly might be the culprit. I just wanted to verify it first by checking like you said. But if that doesn't work, then I may just replace it anyway. I am getting very close to the fix. This probably was the original culprit from a year or so ago too, but I didn't realize it. Thanks.

With fuel pressure primed up good you should be able to see where it is leaking.
Good luck and post back what you find.

Do not hit that start button.
Just jumper fuel pump or.
Just turn key on a couple of times and let pressure build up and watch for leaks.

MT, I havent had a chance this past week to look for a fuel leak. I should be able to in the next week, but one quick thought. Just for info, what would happen if the starter was turned and you inadvertently went past KOEO?

For info.
Not good.
If you try to start it with upper intake off.
Engine could run wide open and self destruct if key not turned off.

I always disable ign before testing it.

Not planning on it, just wondering what would happen with throttle not connected. I figured it'd run wide open. NOT GOOD, especially full of gassy oil.

It's a good idea to pull the coil wire off to disable ign. Another question though. How important is the upper plenum gasket? Meaning is there vacuum through there or is it just a plain old gasket that really doesn't do anything but hold the plenum on? I'm just wondering if you can get a vacuum leak if the plenum gasket is bad.

The plenum gasket needs to be good enough to hold 20 in vacuum.

Use a new gasket when you have it off.

The plenum gasket needs to be good enough to hold 20 in vacuum.

Use a new gasket when you have it off.

I didn't know that. That's why you get the big bucks! :-) My plenum gasket has a few spots that are not there. So, that's another issue I will address properly, but not the major fuel one. I just didn't know the importance of this seemingly trivial part.

Thanks for the tips. I'll post back when I know for sure.