Bad catalytic converter?

[greatmizzou]

While chasing and diagnosing p0101 I believe I have identified more symptoms.

 

I already replaced intake manifold and gasket, fuel lines and filter were redone 8k'sh miles ago,  replaced spark plugs and wires with OEM.  Replaced airfilter and inspected housing.   Intake air MAF elements seem very clean

 

Symptoms are this,   When turning truck on cold and getting onto highway right off my driveway, truck seems really sluggish and unresponsive until I get to 2nd then 3rd gears and get to highway speeds.  I will give it gas but really wont change much in "oomph".   I throw p0101 when accelerating to highway speeds, mainly when towing.   Highway MPG is about 14mpg....seems low.

Fuel smell coming from exhaust.  Smells like its running rich still....which explains the poor mpg.  Oil consumption isnt too bad, seems normal.

 

With all that said im thinking my cats are bad.  They are original stock and probably met their end of life.   Thoughts?

 

2002 chevy 1500 ext cab LT 5.3.  Max tow package 4x4  175000miles

 

 

[Jstevens7700]

Check your fuel pressure sounds like maybe fuel pump starting to act up like my 2005 GMC Sierra 1500. Same exact symptoms. Fuel pressure tester is around 30 or 40 bucks at harbor freight definitely would look into it.

Sent from my Pixel 3 XL using Tapatalk

[Jstevens7700]

Fuel pressure should be around 60 idling. Get someone to rapidly accelerate the truck in other words put the hammer down pressure should drop slightly then return to 55 or 60 still at high idle.

Sent from my Pixel 3 XL using Tapatalk

[CamGTP]

Do people always disregard the code thrown and just start throwing parts at things?

 

P0101 is a MAF code for a circuit range/performance. Not sure how fuel pump or bad cats is the first things that come to mind but whatever.

 

Go ahead and check fuel pressure as it never hurts but I'd be looking into the circuit issue or the MAF sensor itself for a possible cause to that MAF related code. If you know someone with a similar truck, swap MAF sensors as a test to see if it runs better.

 

 

 

[Jstevens7700]

Maybe considering there is no fuel pressure sensor for the computer to read from the Mass Air Flow calculations and thresholds set from the factory may not be met if there is no fuel pressure. If the owner can only get to about 2000 to 2500 rpm and the computer won't let the truck shift until the rpms are lowered which uses less fuel which is exactly what my truck did with the MAF code and probably in the future as the problem gets worse some o2 sensor codes saying the fuel is too lean. Moral of the story my opinion check the fuel pressure or get it checked and go from there. The codes thrown aren't always the problem.

 

 

 

 

[davester]

Also check for broken exhaust manifold bolts.  It's not unusual to happen (at least for the 6.0, don't know about the 5.3), and can result in clean air getting into the exhaust, screwing up the O2 sensor readings, and the ECM will dump more fuel into the engine to try to compensate.  And low fuel pressure will make it worse, but if both are happening, then you'll  probably start getting codes for bank too lean.

 

As for the MAF sensor error, P0101, it sounds like you've replaced everything around the sensor, but not the sensor itself.  It's presumably 16 years old, time to replace it.  If possible, pay extra and get an ACDelco one, these trucks seem to prefer OEM sensors.  I was getting a P0101 error, replaced the MAF with one from NAPA (I forget the brand, but not oem), and it worked fine most of the time, but when it got cold out (as in, Northern Alberta cold), it would throw a P0101 error, I replaced it with a used ACDelco one from a parts truck I have, no more errors regardless of temperature.

[bg1988]

5 hours ago, greatmizzou said:

While chasing and diagnosing p0101 I believe I have identified more symptoms.

 

I already replaced intake manifold and gasket, fuel lines and filter were redone 8k'sh miles ago,  replaced spark plugs and wires with OEM.  Replaced airfilter and inspected housing.   Intake air MAF elements seem very clean

 

Symptoms are this,   When turning truck on cold and getting onto highway right off my driveway, truck seems really sluggish and unresponsive until I get to 2nd then 3rd gears and get to highway speeds.  I will give it gas but really wont change much in "oomph".   I throw p0101 when accelerating to highway speeds, mainly when towing.   Highway MPG is about 14mpg....seems low.

Fuel smell coming from exhaust.  Smells like its running rich still....which explains the poor mpg.  Oil consumption isnt too bad, seems normal.

 

With all that said im thinking my cats are bad.  They are original stock and probably met their end of life.   Thoughts?

 

2002 chevy 1500 ext cab LT 5.3.  Max tow package 4x4  175000miles

lol 

 

try cleaning it First  then do a drive cycle  or   to see if it comes back

 

dude 14MPG is normal   

citing

A: it's a 4x4

B: 2002  ext cab  it is normal to run rich while it's warming up

 

if your CAT was failing you would be getting P0420 stoner code      P0420 = Catalytic converter is stoned

 

 

but you will be getting a P0430 soon as a secondary code (normally that means the MAF is dead for sure )

 

 

be sure to get an OEM parts like Delphi  don't use aftermarket  they will never work right and you need to replace often

[XJ2.5]

I've seen plugged cats trigger a MAF code. It had no power, replaced the MAF with no change, loosened the y pipe bolts and it came right back

Sent from my VS987 using Tapatalk

[swathdiver]

A good scan tool can solve this "mystery" in a minute.  The computer does indeed see fuel pressure, you just need a good piece of equipment to see what it is.  An ODB BT adapter with Torque Pro and a phone works as does the same tool the dealer used to use on these, the mighty Tech-2.  

[davester]

13 minutes ago, swathdiver said:

A good scan tool can solve this "mystery" in a minute.  The computer does indeed see fuel pressure, you just need a good piece of equipment to see what it is.  An ODB BT adapter with Torque Pro and a phone works as does the same tool the dealer used to use on these, the mighty Tech-2.  

No, there isn't any FP sensor.  The earlier trucks (99-03 or so) have a vacuum operated pressure regulator at the fuel rail, and the later trucks (04-07)  have the fuel pump itself maintain the right fuel pressure.

 

The ecm is hard-coded to assume that 60psi is present at the fuel injectors.

 

If the fuel system can't maintain 60 psi (majority of cases, it has lower pressure if something fails), the ecm "notices" in closed-loop mode by opening the injector for X amount of time, cylinder fires, O2 sensor reads lean (as not as much fuel goes in with low FP), ecm opens injector a little longer, repeat until O2 sensor reads a proper burn.  The engine will run, but poorly as the gas doesn't atomize right, and eventually the ecm just hits the limit for how long it can keep the injector open.

[swathdiver]

8 minutes ago, davester said:

No, there isn't any FP sensor.  The earlier trucks (99-03 or so) have a vacuum operated pressure regulator at the fuel rail, and the later trucks (04-07)  have the fuel pump itself maintain the right fuel pressure.

 

The ecm is hard-coded to assume that 60psi is present at the fuel injectors.

 

If the fuel system can't maintain 60 psi (majority of cases, it has lower pressure if something fails), the ecm "notices" in closed-loop mode by opening the injector for X amount of time, cylinder fires, O2 sensor reads lean (as not as much fuel goes in with low FP), ecm opens injector a little longer, repeat until O2 sensor reads a proper burn.  The engine will run, but poorly as the gas doesn't atomize right, and eventually the ecm just hits the limit for how long it can keep the injector open.

Didn't know that about the earlier ones, thanks for clarifying.