2003 Mazda B3000 3.0

I posted another thread earlier this week about sluggish performance up hill. I replaced a bad TPS from that, but before I could get the TPS, the performance dropped a lot. Before, I could drive mostly normal on level ground, but had trouble up hills. Now even on flat ground, I can't get above 20 mph, whether I floor it or try to accelerate gradually.

New TPS
New coil pack
New plugs and wires
New air filter
Cleaned MAF sensor
New fuel filter

The engine is not throwing any codes. It will occasionally throw random codes for misfires, but that seems more of a side effect. There are no codes that I can create consistently.

Bad O2 sensor?
Catalytic Converter issue?

Also, I have the Torque Pro app on my phone with a Bluetooth OBD2 adapter, so feel free to suggest any diagnostics I can do with that.

 

Check your fuel pressure, should be at around 75 psi.
There is a schrader valve on the fuel rail for this.

Fuel pump maybe failing and or fuel filter is blocked.

 

Fuel pressure is 64 psi. I guess that's low enough to cause problems like this?

I replaced the fuel filter last week. I'll look into testing the fuel pump.

 

Actually, I'm seeing information that the fuel pressure for that engine is 64 +- 8 psi. So I think my fuel system is dead on, and not the issue.

 

Yeah, that seems fine.
If I think of something else, I'll post.

 

I would bring it to an auto parts store like advanced auto and they will check for codes for free. It sounds like your CAT.

 

Are you able to easily unbolt the exhaust connection, it's an easy way to check for a blockage.

 

I would spray pb blaster on it like a day before!!!

 

Thanks for the replies, everyone. It was indeed a blocked CAT. I pulled the upstream O2 sensor to relieve pressure and it runs a lot better. I suspect the CAT on the driver side exhaust pipe is clogged, or it fell apart and the material is clogged at the first inline CAT. Earlier this week before the performance totally tanked, I had two tiny holes come up in the weld joints on that CAT. They are sealed now. Also, I installed new plugs on the truck this week, and the three plugs on the driver side all had their terminal points burned away, I assume from excessive heat on that side caused by the blockage.

My strategy for this is to pull the inline CAT assembly. That way I can examine those two, then send a scope up the two exhaust pipes to inspect the other two. I'm guessing I'll clear out the debris from that upper driver side CAT and hopefully be back to normal.