Is MAF sensor failure related to catalytic converter blockage

[dnb5853]

I have owned a 2003 Explorer Sport for over 5 years. It has 121K, 4.0L, 5R55E and a K&N air cleaner element. This vehicle is stock and has been trouble free for the past 5 years except for one time when a split PCV hose split and triggered the CHECK ENGINE light. I have kept up thorough maintenance practice with engine oil changes, coolant changes, fuel filter changes, hose and belt replacements, and transmission oil/filter changes.
This week the transmission started shifting unexpectedly. Both downshifts and up shifts were not occurring properly. A transmission shop ran a diagnostic and did a test drive. There were NO CODES returned and the technician said I had a fuel or exhaust problem. I went to my local Ford dealer, but during the drive there (about 20 miles), the engine lost significant power. By the time I pulled into the dealer, I couldn't drive faster than 20 MPH.
The dealer’s analysis determined that the MAF sensor was bad. They also said that since I had driven it for 2 days with the malfunctioning MAF sensor that all the catalytic converters had been damaged and were essentially plugged up. This model has a catalytic converter on each leg of the Y-pipe and a pair in series ahead of the muffler.

Does this diagnosis sound accurate?
Is it unusual that my CHECK ENGINE light never came on?

The CHECK ENGINE LIGHT properly illuminates momentarily during startup.
Thanks for any help or insight offered.

 

[96eb96]

I have owned a 2003 Explorer Sport for over 5 years. It has 121K, 4.0L, 5R55E and a K&N air cleaner element. This vehicle is stock and has been trouble free for the past 5 years except for one time when a split PCV hose split and triggered the CHECK ENGINE light. I have kept up thorough maintenance practice with engine oil changes, coolant changes, fuel filter changes, hose and belt replacements, and transmission oil/filter changes.
This week the transmission started shifting unexpectedly. Both downshifts and up shifts were not occurring properly. A transmission shop ran a diagnostic and did a test drive. There were NO CODES returned and the technician said I had a fuel or exhaust problem. I went to my local Ford dealer, but during the drive there (about 20 miles), the engine lost significant power. By the time I pulled into the dealer, I couldn't drive faster than 20 MPH.
The dealer’s analysis determined that the MAF sensor was bad. They also said that since I had driven it for 2 days with the malfunctioning MAF sensor that all the catalytic converters had been damaged and were essentially plugged up. This model has a catalytic converter on each leg of the Y-pipe and a pair in series ahead of the muffler.

Does this diagnosis sound accurate?
Is it unusual that my CHECK ENGINE light never came on?

The CHECK ENGINE LIGHT properly illuminates momentarily during startup.
Thanks for any help or insight offered.

A bad maf could create a lean condition causing more gas to be put into the cylinders. Usually if its bad enough to damage cats you would get a code, that is very strange. I don't think cats could be damaged in two days either.

I know this is controversial, but oiled KN filters could cause your maf to get very dirty and cause issues. The very first thing I would do at this point is pull the maf out and clean it. Search the web for the procedure. Be sure to use special MAF cleaner.

Also, you can try disconnecting the MAF sensor (near the air cleaner) and driving it around a bit.

 

[dnb5853]

I had the dealer install a new MAF sensor. The dealer price on cats was VERY HIGH. I'm currently having aftermarket cats installed at a muffler shop.
Thanks for the tip about the K&N filter. I was wondering about that.

 

[96eb96]

I had the dealer install a new MAF sensor. The dealer price on cats was VERY HIGH. I'm currently having aftermarket cats installed at a muffler shop.
Thanks for the tip about the K&N filter. I was wondering about that.

Aftermarket is the way to go with cats, they have a 5 yr warranty.

Now if you were riding around for thousands of miles with a dirty MAF operating at its threshold - that could explain your cats getting fried -maybe.

Either ditch the KN or make sure you clean the maf every year or so.

Good Luck

 

[explorer1995]

Did the problem get resovled by replacing just the maf sensor? I am getting almost the same problem with my 95, once the car gets warm the performance drops and accelerates really really slowly. Put drives no problem first thing in the morning.

 

[dnb5853]

Did the problem get resovled by replacing just the maf sensor? I am getting almost the same problem with my 95, once the car gets warm the performance drops and accelerates really really slowly. Put drives no problem first thing in the morning.

No - there is significant blockage in the cats (according to the dealer flow test). The vehicle can't run over 20 MPH, so it's apparant there is a blockage.

 

[explorer1995]

Thank you for the update, mine def goes over 20 mph just has loss of power after driving for 20 minutes or so.