Why does my engine run rich?

Po172 and po175 and po300

It was the MAF sensor thank you so much

I have a S10 pick with a 4.3L runs rich on both banks does have service engine light on.

Hello,

I have a 95 S10 2.2L automatic. I've owend this truck for about 2 years and have sense done numerous amounts of work to it. Shortly after I purchased the truck I discovered it had a blown head gasket and had the head checked, milled, added new seals, etc. Ever since i've owned this truck it had odd idel problems or acceration problems. I've change the plugs/ wires/ vaccum hoses, etc. Numerous times. I've also installed a new egr valve about 1 year ago. In the past the truck seemed to downshift sporadically at different speeds, however that seemed to clear up after I installed some new vaccum lines. I've also installed a new feul filter & feul pump. Now the truck is hard to start. It will take several seconds to crank and normally needs to be assited with pumping the throttle. Once it starts will will idel ok at times, then it will suddenly change its idel and accerate alittle higher with a low end bog. Or a bog at and speed when accerating. To cure this problem i've attempted to replace the throttle position sensor (twice now) and also the crank sensor. With little results. Also, when I start the truck it will blow feul out the tailpipe. What could be the source of this truck running rich with a low end bog?

Any ideas or suggestions would be greatly apperciated. Thanks -Jimmy

Engine Performance problem
1994 Chevy S-10 6 cyl Four Wheel Drive Automatic

what can cause the pass, side 0f a 4.3 vortec to foul and it is only the passenger side and you can smell that it is runnig way to rich

My truck wont pass smog, and I was wondering what causes a 2.8L to run rich. Please help

2.5 vin code E running very rich. I replaced the oxygen sensor, coolant temperature sensor, map sensor and air sensor in the intake manifold. I can unplug three sensors and make it go into open loop and it runs good, but fuel economy suffers. The tailpipe is shooting out black smoke indicating the running rich. Any help is appreciated.

Did you ever figure this out? I have the same truck and the same problem. I did not know you can unplug three sensors and make it go back to open loop. So I will try that. I know the OBD trick but no code to read just 1, 2 flash.

Truck runs for a few minutes fine the starts to stutter and shut off. You can smell the unburned fuel and it acts like it runs rich and stalls out. Can start right back up and do it again. Not sure if the timing is when the IACV closes or just the computer kicking into “closed loop” (if I got that right). Pretty much all sensors and distributor changed.

No codes and yes fuel pressure.