I have a 1996 Suburban and it has the Vortec 5.7. My problem is that it is running very rich to the point that it has no fuel economy and has a very intense odor of unburnt gasoline everytime it is running. Another problem im having is that when it is idling, after a short time, it begins to have a grey smokey exhaust that has an even more rich smell and the engine misses. the exhause does NOT have an oil smell. I have changed the plugs which has helped with a lot of the missing problem but i am asking for any help in a good place to begin troubleshooting for the running rich problem. I thank you in advance for any help that you can give.

 

Check your coolant temp. sensor or just replace it. It happened to my 95.
The coolant sensor tells the computer the engine temp. and in my case it kept telling the computer that the engine was cold so the computer tells the injectors to run rich. A bad 02 sensor could also be the cause so check them both. And if you keep driving it this way you will eventually plug up your converter with soot, then you will have to replace that too.
Jack

 

I second that.

 

You probably need a new Oxygen Sensor. So you have nothing to lose.
Unplug the O2 Sensor ... pull it and examine it for being fouled with heavy sooting.
Swish the business-end of the Sensor in alcohol and brush it off, clean, with a soft-bristled tooth brush.
Don't use anything else other than straight cleaning alcohol or Electronic Parts Cleaner ... But, don't spray it with a strong stream of Elec Pts Cleaner. Shoot the cleaner into a shot glass and swish the business end of the Sensor around in it.

If you clean it and it works ... you saved a few bucks.
If you clean it and it don't work ... it was dead before you unplugged it!

 

my 96 had somewhat of the same prob. check your fuel pressure, if the regulator is malfuntioning( high pressure) you will run rich, and it will also give you error codes indicating prob. with your O2 sensors

 

First thing i'd check is the coolant sensor, these fail and tell the computer the engine is cold. Then the computer richens the fuel.

 

Is your check engine light on?