shayandude

hey guys, i was driving and the light came on , so i stopped at work, Advance auto parts, and hook the machine up
i got p0171 and p0174
it says system too lean bank one,
system too lean bank 2
the truck is a 02 z71 silverado 1500 ext. cab with 71,000 miles

do they both go out together at the same time?
is that my upstreams?
truck is wanting to die, sucks gas like crazy, and jerks, like mrrrrr.... mrrrrr...... at a red light.
any help is much appreciated.
thank you,
Shayan G.

10gunman

When u get a lean code or a rich code it doesn't always mean that ur O2 sensor/s are bad and besides I don't think both of them would go out at the same time. u should start by remembering when was the last time u changed the fuel filter and start there, also check fuel pressure just a thaugh.

shayandude

hey,
thanks,
i changed the filter, it seemed pretty heavy, so i guess it needed a changing. But the light came back on the next day.
and my gas is disapearing like crazy.
so i just got two 02 upstream sensors, and plugs and wires, and see if that takes care of it
i sure hope so.

mschanha

Have a 99 Silverado 130,000, went through the same thing your seeing, and doing. Replaced O2 sensors, cleaned MAF sensor with contact cleaner, but SES light still came on. Finally broke down and took it to a garage ($$$). They found that the manifold gaskets were sucking air. Morale of the story, when it comes to the SES light it could be a million things.

Maritime

How did the mech. fix the leaky manifold gaskets. My engine light came on last winter. Cleared the code, all summer long the light never came on. First night with temp below 32 the light came on and truck idles rough until it warms up. I have heard that the manifold warps when it gets too cold. Does this sound like your truck??

mschanha

That's exactly what my truck did last year. This year when it got cold, the light stayed on all the time. They replaced the intake manifold gaskets.

shayandude

hey,
yeah wow
it runs rough when cold, ad light goes on and goes off when ever it wants.
changed the 2 sensors, plugs, wires. so the intake manifold gasket is next
lol
thanks guys
its under the aul warantee.

ZX1100F1

Before you go through the expense and hassle of replacing the intake manifold gasket make sure to have the injectors cleaned.
I have seen several cases where the same symptoms that you describe have occurred andwe were able to straighten it out by cleaning the fuel injectors. GM recommends that you use the GM UPPER ENGINE AND FUEL INJECTOR CLEANER but if you do not have access to this system then buy several (4-6) 16oz bottles of Techron Fuel System cleaner and add them to one full tank of fuel then drive untill the tank is nearly empty.

shayandude

thanks zx
i put two bottles of the lucas fuel injector cleaner.
also when its cold, the car idles normally at 500-600 rpms, and all of a sudden it drops close to 0 and comes back up and jerks the whole truck. like a coughing symphtom you could say.
any idea on that?

10gunman

if the truck idles rough it could be a couple of things like mschanha said it could be the intake manifold gasket it could be misfiring due to different things no spark or no air or no gas or a vaccum hose disconnected. you could start by checking the vac hoses but it's kinda cold now for that just an option that is the cheap way or check the iac motor not sure if the silverado has one check the spark plug wires for any breakage and make sure they are all hooked up nice and tight o wait u just replaced them never mind. I know that in the chevy malibu in the 97-03? the intake manifold starts leaking and must get a new gasket done it's pricy if u have it done by a shop and a little time consuming but it seems like chevy didn't do a good job sealing that manifold I'm not sure if it's the same case with the silverado have not seen it often well good luck I'll keep checking to see how u are coming with your search....