Ive got a 99 f150 w/ 4.2. It is throwing both codes p0172 (rich bank 1) and p0174 (lean bank 2). It also has an extreme loss of power. I was wondering if you guys might have any ideas as to what could be causing this although its more than likely a vacuum leak.

 

Lean on Bank1 AND Bank2?
What is common to both banks?
Define lean?
Could be too much air(both banks) OR not enough fuel(both banks)
Vacc leak(gasket or seal) or lack of fuel(fuel filter, fuel pump, fuel injectors)
Now use process of elimination.

 

Check the rubber 90* elbow under the throttle body leading from the pcv valve.It most likely has a hole in it!

 

Checked the 90* elbow and it looked fine. Still no luck. No power at all and around 3.5k rpm it starts making a fast popping noise like it is back firing.

 

Im having the same issue with my 04 Navigator. Im curious if you ever found the problem. I had to P0172 rich in bank 1 and P0174 to lean in bank 2. Rpelaced All PCV boots and lines and replace fuel filter no success! Im spinning my wheels at this point!!

 

That's what I call an engine that can't make up it's mind. Lean on one bank and rich on the other. Now if you could just get Bank 1 to start communicating with Bank 2 the ECM might solve this problem using adaptive strategy. I'm looking at clogged cats on these engine. You can pull the pre-cat O2 sensors and put in a exhaust gas backpressure tester. You should see less than 1lb at idle. Then bring the RPM up to around 2.5K RPM. You should see less than 3lb. If the needle jumps way up as you raise the RPM your cat is clogged and it's time to head to the muffler shop. A good muffler shop should have the exhaust backpressure tester. The shadetree way is to loosen the bolts at the flanges between the exhaust manifold and the cat. It's noisy, but if the truck performs better above 3K RPM you know your cat is clogged. You many have to do one side then the other if you don't know which side is at fault. You have to drive the truck to see if having the exhaust unbolted helps performance.

 

Im going to try the shadtree way tonight! I was worried that it may have been the CAT in the beginning but everyone was pointing me in the direction of vaccum leak and fuel delivery. I did have a leak at the elbow in the PVC line where it goes into my manifold but it didnt fix my performance issue at all so i guess but it wasnt a waste of time since it was leaking! Thanks for the advice! Hopefully this will sove it....

 

The F150s have P0171 and 174 from bad hoses causing vacuum leaks They also clogged EGR ports with high mileage. AutoZone sells a lot of unnecessary EGR parts to Ford truck owner when the real problem is soot and tar in the two intake ports. They also have a lot of misfires due to dead COPs. To kill a cat you have to feed it bad cat food(raw fuel) for a long time. When it gets that bad the CEL will flash telling you to fix it SOON. If you don't your cat will die. The symptoms from a bad cat are different than the other problems Fords usually have. There is money to be made fixing Ford EGR, COP and lean bank1 and 2 problems. I love Fords

 

It was definitly a plugged catalytic converter. I took a shot at the one that seemd to be a lot hotter after it ran a minimal distance and the power increased significantly. Definitly louder but i was able to just drill a few holes in it to get thru till i can get the new one shipped to me later in the week! Thanks for the help and advice!!

 

Changing the cat is a good idea, but only if you're feeding your cat good cat food. Have you fixed the problem that killed the cat? If not you'll be going to another funeral soon.

 

Well the To Rich in Bank 1 I believe was casued by the PCV leak, which if it was feeding it to much gas over a period of time could that possibly have caused the converter to plug up?? The CAT that was plugged was on the same side as the bank that was being fed rich?? Also I believe this is what caused a melted DPFE sensor from getting bad gas emissions from the plugged converter. Its almost running me in a cirlce and its hard to tell if the problems were all related by a domino effect or seperate issues all together?? Any insight is definitly aprreciated.

 

What happpens when a cat gets clogged? Where does that exhaust gas go if it doesn't go out the tail pipe? It has to go somewhere so it looks for the next easiest place to escape. On a "V" engine it can't go out the exhaust on the other Bank so it has to escape through the exhaust valve on another adjacent cylinder that has its' exhaust valve open, but the exhaust on that cylinder wants to get out(not in) so you have a problem. That's why the vehicle acts like it's having an asthma attack when the cat is clogged. A DPFE has to get real HOT to melt. There are rubber hoses between the EGR tube and the DPFE. Those must have melted or burnt too. Yes, this could have been a long chain of events that started with a cracked hose. If you had fixed that $5 hose sooner you might have avoided most of these problems.

 

F150 2003 code p0172 and 174 what is the problem what is the problem
Help

 

Vacuum leak.

 

https://www.obd-codes.com/p0172
https://www.obd-codes.com/p0174