93 not running right, need help UpDate, Code 51.
 

Hey guys, my truck started running poorly a couple days ago and it is getting worst.
The check engine light has not come on.
It will start and idle well.
It will accelerate well.
When maintaining speed (slight throttle) it hesitates and seems to lurch.
When coming off the gas to coast to a stop, it idles way down and today it died a couple times. It always starts right back up and idles fine in park or neutral.
I believe the odor I detect when it is running is rich.
My thoughts; since it smells rich I think it may be a spark issue. I plan to replace the plugs, plug wires, distributer cap, and rotor.
Since it hesitates under partial throttle, it may be a fuel delivery issue, but I don't know.
What do you guys think?
I plan to try and check for codes sometime today.

Thanks

mine is having slightly similar issues, i have gone through all the normal stuff (cap rotor plugs wires oil change pcv iac thermostat etc) at this point i suspect the egr valve, ima try and clean it up first and then replace, if your not short on cash, i would throw that in the loop of things to change right off the bat...just an opinion, i am no pro lol

Tons of possibilities. First I would suggest to take a look at every wire, hose, connection. It can be a vacuum leak to a bad coil cap rotor. A tune up would be a good start.

Ok, I ran the codes and got #51 fuel system lean. So, any idea what may be causing this? I thought it smelt rich, which would be lean, right?

Problem solved, it was a bad O2 sensor.