97 LX450 / backfire / at start up (8 Viewers)

[Jim S.]

After engine cycles a couple of times for oil pressure and initially fires I get a loud pop. Had a 0420 code and replaced O2 sensors. I haven't had the code for several hundred miles. Thinking something something is up with the Cats, They are original and the truck has 130,xxx + on it. Truck is supercharged but I don't see that as an issue. No smog requirements in my part of Arizona and I could try an after market Cat, however I don't want to start throwing money at parts without a definitive cause.

Thoughts and advice appreciated.
Jim

 

[ChaseTruck]

After engine cycles a couple of times for oil pressure and initially fires I get a loud pop. Had a 0420 code and replaced O2 sensors. I haven't had the code for several hundred miles. Thinking something something is up with the Cats, They are original and the truck has 130,xxx + on it. Truck is supercharged but I don't see that as an issue. No smog requirements in my part of Arizona and I could try an after market Cat, however I don't want to start throwing money at parts without a definitive cause.

Thoughts and advice appreciated.
Jim

Not sure I'd think of the cat(s) first hand; I'd suspect something like too much unburned fuel, which is then combusting either in the header or in the cat(s)?

 

[Jim S.]

Not sure I'd think of the cat(s) first hand; I'd suspect something like too much unburned fuel, which is then combusting either in the header or in the cat(s)?

I was thinking that too, Possible bad injector? Plug ,wires and distributor cap were replaced a couple of years back and we don't put a lot of miles on it.