dogdog130

my girlfriends dads 5.4 is dieing randomly when ideling i got to give it gas to keep it running. now seems like running on half cycl but engine has 15k on it. replaced fuel filter was very dirty and idel air control. only 2 codes are p0171 bank 1 lean and p0174 lean bank2

dogdog130

anyone

rpm121370

check all vac lines for leak, check PCV tube and the ends for being very soft or leaking

Good Luck
Ron

Art.F96

Sounds like IAC, or as person above mentioned a vacuum leak somewhere, check hoses, maybe even a gasket somewhere at the throttle body.

dogdog130

Replaced idel air control and i replaced pcv valve going to remove throttle body today and check the back 90 for cracks

charliedyal

Like everyone else, I believe its a bad vacuum leak. Check the other hoses on the back of the manifold where you replaced the IAC and PCV hoses to be sure nothing has come loose. Is it skipping at all? Or is the problem just at idle?

4x4dave

This is a lean condition. As mentioned above look and listen for a vacuum leak.

Also - A bad exhaust leak can also trigger these codes. Basically some of the exhaust gases can escape and will be unmetered by the 02 sensors, so the o2 sensors are not reporting the correct gas mixture. When the o2 sensor reports more air than normal it triggers a CEL.

Also, you said your fuel filter is very dirty. It's very likely your injectors are so dirty they cannot inject enough fuel causing the lean condition. You may want to remove the fuel rail and inspect the condition of the lines. Clean evreything out and add some fuel treatment.

It probably wouldn't hurt to get new plugs installed as well.

kennyS

My 97 4.6 was doing this also and it turns out my negative battery cable needed to be tightend and it solved everything. still have to do it every now and again because i havent replaced the cables and all.

FCVFD

I just fixed the same problem on mine yesterday had 2 vacuum leaks one in the hose that goes in to the left of the throttle body and the one that was making it stall and idle real bad was the pcv elbow under the idle air control module. Also mine is a 5.4

norcal screw

I had a situation like this and it was the hose from the incoming air to the IAC. there is a little silencer box that I remove and used a piece of heater hose to replace it. With both banks lean I would have to say it is most likely a Vac leak or possibly a sticking open EGR valve.