Modded Mustang Forums banner

1 - 12 of 12 Posts

·
Registered
Joined
·
929 Posts
Discussion Starter #1
Last week I finally installed the used catted X pipe I bought last year. No idea what brand, but it's 2.5" mandrel bent Stainless with 2 high flow cats. It kinda looks like a BBK or Bassani. After 5 days of driving the CEL came on. I pulled the code and it said "catalyst efficiency below threshold". I don't remember the actual code number, but I read somewhere that even some hi-flow cats may require MIL eliminators like an O/R pipe does.

Is this the same code an O/R pipe triggers? Is this a common problem for most catted mid-pipes with just 2 converters?
 

·
Registered
Joined
·
1,318 Posts
I have heard of some catted mid-pipes having this error. I think it depends mainly on what brand the converter is. My SLP high-flow cats have not thrown a code thus far.
 

·
Registered
Joined
·
3,415 Posts
Last week I finally installed the used catted X pipe I bought last year. No idea what brand, but it's 2.5" mandrel bent Stainless with 2 high flow cats. It kinda looks like a BBK or Bassani. After 5 days of driving the CEL came on. I pulled the code and it said "catalyst efficiency below threshold". I don't remember the actual code number, but I read somewhere that even some hi-flow cats may require MIL eliminators like an O/R pipe does.

Is this the same code an O/R pipe triggers? Is this a common problem for most catted mid-pipes with just 2 converters?
Most aftermarket catted mid-pipes do not clean up the exhaust enough to keep the catalyst monitor happy. You can have the rear 02s turned off with a tuner or run MIL eliminators
 

·
Registered
Joined
·
929 Posts
Discussion Starter #8
It was originaly the 49 state standard 4 cat system. I doubt the cats are plugged or fouled, but I suppose I could try a mild Seafoam treatment to clean the cats. The X pipe came off a '99 Roush with 39K miles, but I don't know if it was a factory Roush piece or not. I'm thinking along the same lines as tbirdscwd and probably just need to add MIL eliminators for now until I get a tuner. It was kinda interesting that I drove a fair amount the first 4 days without issue on 1/4 tank of E10, then I filled up with straight 87 Unleaded and 40 miles later it tripped the CEL. They say E10 burns "cleaner", so I wonder if the aftermarket cat efficiency was so close to borderline acceptable that the switch to a non-ethanol fuel made the difference and set off the CEL?
 

·
Too Soon, Junior!
Joined
·
3,830 Posts
It should be P0420 and P0430 codes for the cats. I agree the high flow catted X just didn't burn enough of the excess fuel to keep the rear O2 sensors happy. Let me know if you need a set of MIL eliminators, I have a TON of them sitting here.
 

·
Registered
Joined
·
929 Posts
Discussion Starter #11
It should be the P0420 AND P0430 codes. I agree the high flow catted X just didn't burn enough of the excess fuel to keep the rear O2 sensors happy. Let me know if you need a set of MIL eliminators, I have a TON of them sitting here.
I think the only code was 420 (bank 1?). I gather it didn't throw the code for both sides, which I imagine is not uncommon and would depend on the actual condition of the individual cats and/or the individual sensors. The car they originally came off of had a cracked header on one side which may have fattened up the fuel mixture on that side and consequently been harder on that converter. If the code returns consistently I'll PM you about some MIL elims.
 

·
Registered
Joined
·
2,709 Posts
throwing a light with or/x pipe is common
 
1 - 12 of 12 Posts
Top