please help at end of rope!!!

[mikemedic3]

Well I know it's been discussed and I have searched extensively, but. My truck 03 Yukon 5.3 not flex fuel, a while back threw the maf code and started to idle rough while in gear, so with a 140000 on her I changed it, for it to come back with intermittent 304 and consistent 161 171! so after research I changed the intake gasket, checked intake itself, barely in spec for warp. After which maf code gone but bank 2 o2 161 171 still there with rough idle still there in gear!!! So I changed the o2's both after cat with no change, both still throw code, (heater malfunction). So I checked pcm1 fuse ,good, checked wires from o2 sensors and found the pink wire was broken on bank 1 sensor2, so I respliced. Went down road for about 5-6 miles and check engine light came on!!!!!!!! po161,171 still with rough idle. I am at a loss, I can't afford to send to a garage, I don't have a scan tool to read anything other than codes!! Really need help with this it is also throwing a 304 code too (lean cylinder 4) no bank given. What the hell can this be?????????

 

[mikemedic3]

Anyone? Anyone?, Bueller?, Bueller?

 

[kschumake83]

my 2000 silverado threw a code for bank 2 sensor 2 so I threw a new o2 sensor in. It didn't work, so I did a little research there and I was told that where the rear o2 sensor wire goes around the trans they tend to pinch. I never verified this as I only have to pass an emissions test once a year, and if you drive it like you stole it for a couple miles it will heat up the sensor and the code will go off. So I would immediately drive to my inspection mechanic and get it inspected, then I would return to driving like grandpa with the check engine light on.

 

[JennaBear]

O2s after cat don't do anything with fuel, P0304 isn't lean cylinder four it is misfire.

cylinder 4 is on bank 2
1357 on bank 1
2468 on bank 2

Could very well be fuel pressure that is causing rough idle.
P0304 and P0171 Check fuel pressure, if low, start from there...at idle it should be about 50psi.

 

[2005SnowKon]

Try cleaning your mass airflow sensor. .

Sent from my SPH-L710 using Tapatalk 2

 

[mikemedic3]

Thank you all for the replies, will try fuel pressure end of it. Seeing I replaced Maf it shouldn't be that! Not that it couldn't be bad already. but that code went away after i replaced the intake gasket.

I heard about the wires getting pinched and tried to follow them. But after it goes over the trans I can't see until it comes around by rear of engine, what I can see the loom is ok with gentle bends.

This is the problem, I have checked, replaced all that I could think of and the damn thing is still acting up. I will get a pressure guage today and try that, I have to replace the water pump on the wifes blazer today, cause of course that is giving me trouble too, just did the intake gaskets on that, because it was old faithful on the top! Get that done and now the pump is leaking. It just never ends!! I told her I am getting her a new truck one part at a time! The blazer I have done over the past 3 yrs the alternator, bothfront wheel bearings, master brake cylinder, then of course broken rear brake line! thermostat, intake gasket and yesterday the idle pulley and today the water pump. Still need to do the rear pinion bearing, and fuel sending unit! Really wish I had the money for something new!!!

 

[JennaBear]

MAF is unrelated to fuel pressure. Your pump might be going out.

Sent from an ice cream sammich.

 

[mikemedic3]

Here's another question for those that think it's the fuel system IE pump or such. What does that have to do with a heater circuit malfuntion code for the after cat sensor's? I don't see how a weak fuel pressure/lean condition would trip that code? I am just tring to learn.

 

[saltygq]

MAF is unrelated to fuel pressure. Your pump might be going out.

Sent from an ice cream sammich.

X2, my truck was giving rough idle and in gear plus the random cylinder misfire. From what you explained I would change the pump, I banged on the tank a couple times and it started working again. Maybe try that and see if it runs better, if so you will know for sure its the pump. Or better yet rent a fuel pressure tester from autozone and test the pressure at the rails. Should be over 50/55 IIRC.

Hope you get it fixed soon.

 

[mikemedic3]

checked the fuel pressure and it's spot on at 50. So doesn't seem to be fuel. I am really at a loss here.