Hello all. I have on 02 xlt with the 4.2l. I had the motor replaced about 6000miles ago. From the intake up is old parts from motor and down is all brand new. It has had a check engine light on since motor was replaced with the 0171 and 017r lean bank 1 lean bank 2. It will drop idle from 650 rpms to about 100rpms then back up again while sitting at a red-light with foot on brake. It also will die periodically while in reverse with foot on brake. Truck gets about 8.5 miles to gallon in town driving and about 11 on hwy. Shop that put motor In said it was vacuum leak which they fixed. Still same codes. Then it was ignition coil pack. Same codes. Then anything and everything electric. Same codes. New hoses all around. New evap system. New gas cap. New o2 sensors. The list goes on and on. Shop will no longer return my calls so I need help from you all please! Thanks in advance

 

Easy peasy solution, most likely.

You need new intake manifold gasket and isolator bolts. That’s a rite of passage for owning a 4.2.

Reading this, I wish you had come in for advice before firing the infamous Random Parts Cannon at the engine. Pretty much nothing you replaced correlated to those two codes.

 

Johnny Paycheck

Thank you! I will have my new mechanic look at it. I was following the advice of my old mechanic on the 'parts cannon firing'. He got about $7500 out of me on it before he quit responding. Thanks again.

 

Before chasing any vacuum leaks, make sure the MAF sensor is working properly. Since the codes are for both sides, it is like something like the MAF which affects both sides of the engine.

Also check the fuel pressure and do a smoke test to verify if any leaks actually exist.

 

smoke test has been performed. Fuel pressure also which was 32 psi. Right in middle of parameters of what it should be. Ty for suggestion

 

Try MAF cleaner. Don't touch the thin wire inside they are delicate and can be damaged.
You likely have "security" screws holding the MAF in place and these will need to be removed.

 

DaddyM75,

It’s been a few days since you last posted. Have you resolved this issue and if so, please post the solution? Feedback is important so that we all learn solution paths to these issues.

Thanks in advance

Jimboy

 

I had a new pump, injectors and a new throttle body put in and now p0172 and p0174 codes. Rich bank 1 and 2. Had it back at mechanic and replaced all o2 sensors. Now the P0172 has popped back up. I am at a loss and so is my mechanic at this point. His OBDII isnt showing anything else.
Thank you

 

Did you clean the MAF?

 

New MAF also put on. Sorry, forvot that with original post