Bad primary cat? - Toyota GR86, 86, FR-S and Subaru BRZ Forum & Owners Community

blsfrs · 02-26-2022, 05:23 PM

I have a a couple of signs that the primary cat has gone bad. I just want to confirm my suspicions before I knock it out. There's loss of power that's getting worse the last few times I the car took the car out. The upstream pipe temperature is higher than downstream. I was holding 2500rpm when the picture of the scan tool was taken. Last year, when I had the rocker problem, I had to drive the car 20-30 miles with a misfire which, I know, is death for a cat . It's an afe catted header .

All in favor of knocking the cat out say "aye"

NoHaveMSG · 02-26-2022, 05:33 PM

Yeah, I would say cat needs to go. If you can get the car on jack stands and check it with a cheap temp gun. Should be pretty obvious that way.

blsfrs · 02-26-2022, 09:00 PM

Quote:

Originally Posted by NoHaveMSG

Yeah, I would say cat needs to go. If you can get the car on jack stands and check it with a cheap temp gun. Should be pretty obvious that way.

Thanks. Did that. Near as we could tell, looked like 200*c difference pre vs post cat.

NoHaveMSG · 02-26-2022, 09:11 PM

Quote:

Originally Posted by blsfrs

Thanks. Did that. Near as we could tell, looked like 200*c difference pre vs post cat.

Some quick googling shows the outlet should be a touch hotter then the inlet at the cat, which I didn't know. So for sure sounds plugged.

blsfrs · 02-26-2022, 09:59 PM

Quote:

Originally Posted by NoHaveMSG

Some quick googling shows the outlet should be a touch hotter then the inlet at the cat, which I didn't know. So for sure sounds plugged.

I found a couple of videos on back pressure testing. Just for giggles, I try it as further confirmation.

Grady · 02-27-2022, 10:22 AM

Time for a gut job!

blsfrs · 02-27-2022, 09:56 PM

Good increase in power. Still wants to bog down at higher rpms. Seemed to improve after a few wot pulls. I'm guessing the ecu will need a couple of drive cycles to figure itself out.

Jabbing the throttle showed back pressure with my handy dandy DIY gauge.

The primary cat was toast. It had come loose from the inside of the housing. Still took 45 minutes to get it out.

02-26-2022, 05:23 PM	#1
blsfrs Senior Member Join Date: Dec 2018 Drives: 2013 frs base Location: central Virginia Posts: 1,428 Thanks: 2,637 Thanked 1,421 Times in 676 Posts Mentioned: 13 Post(s) Tagged: 0 Thread(s)	Bad primary cat? I have a a couple of signs that the primary cat has gone bad. I just want to confirm my suspicions before I knock it out. There's loss of power that's getting worse the last few times I the car took the car out. The upstream pipe temperature is higher than downstream. I was holding 2500rpm when the picture of the scan tool was taken. Last year, when I had the rocker problem, I had to drive the car 20-30 miles with a misfire which, I know, is death for a cat . It's an afe catted header . All in favor of knocking the cat out say "aye" Attached Images

02-27-2022, 09:56 PM	#7
blsfrs Senior Member Join Date: Dec 2018 Drives: 2013 frs base Location: central Virginia Posts: 1,428 Thanks: 2,637 Thanked 1,421 Times in 676 Posts Mentioned: 13 Post(s) Tagged: 0 Thread(s)	Good increase in power. Still wants to bog down at higher rpms. Seemed to improve after a few wot pulls. I'm guessing the ecu will need a couple of drive cycles to figure itself out. Jabbing the throttle showed back pressure with my handy dandy DIY gauge. The primary cat was toast. It had come loose from the inside of the housing. Still took 45 minutes to get it out. Attached Images

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