Chvy2003man

I'm new here and I'm hoping someone can help me out with some issues I'm having with my truck. It's a 2003 Silverado LT Z71 with 86k that I bought 2 years ago to replace a 95 Silverado. It's been a great truck with no issues until about 6 weeks ago. Check engine light came on and it ran like crap at idle, misfiring, almost stalling. Smelling bad. I scanned it with my scanner it said O2's so I replaced them, cleared codes. Light came back on, said mass air. Replaced it. Ran good for approx. 20 mins. back to square one. replaced fuel filter, cleaned throttle body like a mechanic friend told me to, still running bad at times, although it sometimes runs good. Check engine light is still on and it still says it needs o2's, mass air, and is missfiring, and running lean in bank one. I replaced the plugs too (sorry forgot about that). Seems to have most of its issues at idle although my highway mpg has tanked down to 9 mpg when it's really bad from high 20's . I'm at a complete loss here. Any ideas??

s34n

did it give a specific cylinder that is misfiring or just a random misfire. with these trucks they have the coil over plug concept. so a coil pack might have gone bad. im not too sure about the other problems. did you buy direct fit 02 sensors or universal?

Chvy2003man

It said Random multiple misfires and the O2's were direct fits not universals.

s34n

mdtahoe is a pretty good person to talk to about this. might want to shoot him a pm.

country_09

my moms tahoe was random misfirin and we replaced the plugs and got a set of new wires. Did you use iridium plugs or just any ole kinda plug?

Chvy2003man

I used just any kind of plug for now to see if it made any kind of difference. Which it didn't.

s34n

try delco iridium plugs. and i believe 8 or 8.5mm wires

MDTAHOE

You need to post at least the specific code numbers and descriptions if you have them. Just because you have a code for a sensor it does not mean that sensor is bad, it only means that the sensor is seeing the problem.

country_09

the newer silverados require the iridium spark plugs...or they'll run like crap. I had to learn that the hard way..switch to the ac delco iridiums and it'll run great

Chvy2003man

Sorry, I've been working long hours. Thank you for responding. There are 4 codes. Here's what I have....

Codes 1&2 are both this exact one
P0131
O2 Sensor Circuit
Low Volts (Bank 1 Sensor 1)

Code 3
P0171
System too lean (bank 1)

Code 4
P0300
Random/Multiple Cylinder Misfire detected

Those are all the codes that it currently has. It seems to be running rich to me....you can smell it, see it, it's running rich. Also, the engine light went out again on my way home from work last night, but I haven't done anything else to it so there's no reason for that. I was basically pulling into my driveway so I'm not sure if it's running any different. Didn't seem to be.

I have a freeze frame as well from code P0131 if you need me to type all of that out? Just let me know.