Hey guys, I just recentely bought a new code reader to scan my 99 4.3L 5 Speed S10 becuase it has been running like crap and the check engine light has been coming on. I scanned my truck and the code reader gave me two codes P0171 System too lean (Bank 1) and P0300 Random/Multiple Cylinder Missfire Detected. Before this i changed my plugs and wires, distributer cap and rotor, cleaned my Fram air fliter, blew off my MAF Sensor and changed my gas filter. I then deleted these codes and went for a 20 minute ride out the high way and came back to scan my truck again. It then gave me 4 codes. P0101 MAF or VAF A Circuit range/performance, P0131 02 Sensor Circuit Low Volts (Bank 1 Sensor 1), P0143 02 Sensor Circuit Low Volts (Bank 1 Sensor 3) and P0151 02 Sensor Circuit Low Volts (Bank 2 Sensor1). I was told to clean my MAF Sensor with break clean so im going to try it. Any help would be greatly appreciated I have no idea what to do. Thanks!!!

reset codes and cheack all plugs then take it for a ride then check it if u get a strage reading always reset and see if it shows the same codes again the codes you have i would be chcking my plug gap to make sure that it is 60 thousanths and that none are cracked or miswired

Hey Mattboy,

You may want to search this forum for EGR issues. Appearently carbon build up in the EGR valve can cause many of the codes you have listed. You may also want to search for P0300, I recall a couple of posts which traced this issue down to carbon in the EGR valve.

Good luck,

Sparky

yea right on thanks... After i cleaned my MAF althought i couldn't see any build up in it my truck suprisingly ran alot better! just one stupid thing i would never thought it would be now the only code im getting is enging missfire. I just put new Bosh platinum +4 plugs in it so i'll have too pull them all and check the gap THANKS AGAIN!!!

Also I did pull the EGR valve out and scraped off as much carbon as i could didn't seem like alot but who knows how much is inside of it but the little valve or whatever was opening and closing pretty well... is there anything i could flush it out with u know of?

Bosch plugs are known to cause performance problems in these engines. Possibly the worst plug that you can use in a Vortec. I would return them and get a set of AC Delco plugs. Same thing with the distributor cap, a lot of people have had problems with the cheaper ones, best to go with AC Delco on the cap, too.