Need help with Codes, Exploder running rough

[maelstromracing]

It's a friend of mine's Explorer that I need help on. It's 99 4.0 SOCH. I am getting 4 codes (Didn't pass emissions)
P0174 System Too Lean Bank 2
P0171 System Too Lean Bank 1
P0300 Random Multiple Cylinder Misfire Detected
P0420 Catalyst System Effieciency Below Threshold Bank 1

Any ideas where to start? I am thinking it is running lean from a messed up 02 sensor, clogged fuel filter or injectors or fuel pump not giving a lot of pressure or possibly a vacumm leak. Car runs like crap when it is cold out until it warms up. Air Cleaner is new. I haven't check the plugs yet. Thanks!!!

Lee

 

[huskyfan23]

I'd guess o2 sensor(s), DPFE or EGR faults.

 

[thundertiger]

Inlet manifold gaskets

Hi My Ex was running rough a couple of weeks ago so I had a look on the net and found out about the Inlet Manifold Gaskets. Because the manifolds are plastic and where they mount on the engine is metal the rates of expansion by heat are different which causes the gaskets (these are 6 'O' rings on the bottom part and 2 rubber gaskets on the upper part) to scrub only a very small amount but after 83000 miles as mine has done it takes its toll. I checked for fault codes as the engine check light came on and 174 came up system too lean bank 2. This is because air is being sucked in past the gaskets and is not being metered by the maf sensor. Any way with the help of my haynes manual and about 2 hours I succesfully changed the gaskets myself and now she runs as good as new. I hope this helps . Steve

 

[thundertiger]

by the way mine ran better once it had warmed up before i changed the gaskets

 

[Glacier991]

sounds very much like the manifold seals.... and maybe something else thrown in. Don;t get excited about changing 02 sensors... they MAY just be telling the truth.

 

[maelstromracing]

I was thinking it wasn't the 02 sensors since there was a fault code with them, but rather they were 'stuck' at a certain voltage. I will check for the intake gasket leak. Could you hear the hiss of the intake leak? Thanks!!