Had this nice leak for a while and before I take it in to the shop and pay for a vacuum leak test I'll like to ask for you're guys opinion I have the P0171 P0174 so I've changed all 4 sensors (it has 150,xxx so I taught it was time) changed the vacuum line that has the pcv valve and goes to the back on the intake manifold changed the vacuum line that goes from the top of the manifold/tb to some valve thats right above the booster cleaned the maf and the idle air control valve also ive just changed the plugs. The idle is seems perfect no hesitations what so ever but it still throws the codes and with CA new DMV laws I cant get a 3 month permit anymore o with that said were else should I look or should I just take it in

its an 01 expy 5.4 awd/4x4 with 150,xxx

what will i look for if I think its the manifold it has one of those plastic ones???

 

Unmetered air can enter the engine through a vacuum leak, a dirty airflow sensor that is not reading airflow accurately, an EGR valve is not closing and is leaking exhaust into the intake manifold, an EGR valve that is allowing too much flow (because the EGR differential pressure sensor that monitors EGR flow is faulty and is under-reporting EGR flow

 

Exhaust leak close to the sensors can cause those codes too.

Try an un-litpropane torch around all suspected vac leaks while the motor is running, change in RPM=vac leak. Fix as needed.

I hate Cal smog tests! If you clear the codes it will have a P1000 if the proper drive cycles have not been completed and that is a fail on the test. I don't think that the budget code readers will pick up the P1000, so make sure you are good before you go in.

Also how are the brakes? A leaking power booster will throw those codes too.

Good luck
Jim

 

Ive used my superchip cortex to clear the codes that were i saw the p1000 ive changed the hose that goes to a valve on top of the booster and the brakes do feel a lil better but i still got the check engine burning bright

 

Kr619,

Hving the same issue with my 04 FX4. any resolution ? ? ?