My truck keeps melting its cats!!!

[blk12b]

Someone please help! I recently drove across country in my 2000 4.0 explorer. I barely made it. When I arrived my cats were melted and the dealership said my fuel pump was bad. I replcaced my cats and on the way home i took a look under my truck and my new cat was glowing red! Can this all stem from a bad fuel pump? Also it idles really ruff and stalls out after a bit. Sometimes it wont even start. These are the codes it pushed out. P1131,1151,0171,0174 Lean Codes Bank 1 &2.

[shorod]

Sounds like you have a bad vacuum leak or misfire. You could possibly have a faulty Mass Air Flow (MAF) sensor as well.

Per the factory service manual, some items you need to check are:
Electrical:

• Short to VPWR in harness or HO2S
• Water in harness connector
• Open/Shorted HO2S circuit
• Corrosion or poor mating terminals and wiring
• Damaged HO2S
• Damaged PCM

Fuel System:

• Excessive fuel pressure
• Leaking/contaminated fuel injectors
• Leaking fuel pressure regulator
• Low fuel pressure or running out of fuel
• Vapor recovery system

Induction System:

• Air leaks after the MAF
• Vacuum Leaks
• PCV system
• Improperly seated engine oil dipstick

EGR System:

• Leaking gasket
• Stuck EGR valve
• Leaking diaphragm or EVR

Base Engine:

• Oil overfill
• Cam timing
• Cylinder compression
• Exhaust leaks before or near the HO2S(s)

If you keep driving the truck with the issue, the new cats will be shot in no time (if they aren't already!). Did the rough idle occur after you got home, or was it already there when you put the new catalytic converters on?

-Rod

[blk12b]

Rod...

Thanks for your help on the ideas so far. The rough idle started as soon as they took my truck off of the lift. It ran better but it got worse. I dont drive it at all now. But my cats were glowing red after a five minute drive! It started out with four cats and i went down to three could that be the problem? The dealershiip says its the fuel pump. They say it pressures up and then bleeds off. Get this also my car wont run at all with the spark plugs in the correct order but when i switch them and put them in the wrong order it runs but runs rough and super hot. Thanks for any help u could give me!

[shorod]

The dealer told you the pressurizes, but then bleeds off. Is this with the key turned to the "Run" position, or with the vehicle running? If this is just with the key to run, this is not indicative of a faulty fuel pump, but rather a faulty fuel pressure regulator or leak somewhere (fuel injector stuck open, etc). If the fuel pressure never reaches specification, then the first step would be to replace the fuel filter before condemning the fuel pump.

You may want to try removing the Sensor 1 oxygen sensor (pre-catalyst) from each cylinder bank and see if that improves the way the engine starts and runs. If that does, then it would seem you have an exhaust restriction.

Also, check the engine timing. If your timing is off, that could cause just about all the symptoms you describe, except the fuel pressure issue.

-Rod