Good afternoon All,

Finally i got new cats on my wife's 97 5.4L v8 4x4 expy, however i am getting codes p0174 and p0171 "system too lean on bank 1 and system too lean on bank 2.

I put a new MAF sensor & applied fuel injector cleaner into the tank, however this has not helped at all and engine is still missing...

I changed all 8 spark plugs about 3 weeks ago....

any ideas guys? it's like is loosing power .......and shuts off on me sometimes when i turn AC on.......

Also the pulley tentioner i know is bad cuz is making squicky noises......could that be part of the miss?

Again guys your help is much much appricated thanks a bunch!

 

Sometimes the plug comes out of the airbox where the MAF goes. Heard of that causing problems like you describe.

If that isn't it, I would look at a vacuum/air leak as the source of your problem.

 

Sounds like someone used cheap universal cats instead of Car Sound (MagnaFlow) or Imco direct fits. Both of those codes are O2 sensor codes from the exhaust. Might be an exhaust leak at the manifolds but sounds more like either a change in the O2Sensor placement or a light load cheap cat.

 

Those O2s are before the cats. If the cats were not working right, he would get an emissions efficiency code.

 

While both of the codes emanate from the forward O2 sensor, it doesn't mean anything about the operation of the cats.

 

bad bad news....it left me stranded this morning with wife n kids......had to get cab ...go get superduty, then go to autozone and buy fuses then drive back home without it luckely shutting off again....

FUSE # 30 below steering wheel on fuse box keeps popping...what can cause that?

service engine light on ....codes p0171 & p0174 .....