Hello,

This is my first time posting on this forum, as well as the first time owning a Ford. I've previously driven two Chevrolet trucks, and can say that I'd rather not do it again.

On Monday, I bought a 2004 F150 Lariat 4x4 (For which I'm still waiting for the title). The price seemed right, but it doesn't have catalytic converters. The seller showed me that it was able to get through emissions, but it did dispay the 2 corresponding cat codes, P0420 and P0430.

At some point, I will need to go through emissions (in the Phoenix Metro Area), so I'm wondering what I need to do here.

According to this diagram here, it shows 2 pre-cats and 2 full-cats, with O2 Sensors before and after the pre-cats.



Underneath my truck, I see NO cats at all, and 2 out of 4 O2 sensors. The exhaust configuration is 2 straight pipes into a Y-pipe, SISO. (I wonder if I could get away with just installing one Catalytic Converter and O2 Sensor, or if I need both cats and pre-cats)

Do I need to re-install some hardware, or find a way to permanently tune out the codes and get through emissions?

Thank you for your help.

 

First off, welcome to the site.

As you correctly noted, our '04's came with 4. In California you'd need 4. You can replace with two cats preferably aftermarket to save your wallet. On this forum Magnaflow 94106 & 94136 (same thing but has an O2 bung installed. You can buy universal versions of the factory cats from Magnaflow as well. I have the 94106's myself but mine are throwing codes due to a poor weld job, but I'm also becoming suspicious they might be damaged as well. If you are hooked up via OBDII for emissions you can't tune out the codes. It will result is "system not ready" thus resulting in a fail.

Hope that helps.

 

Thanks for the answer.

So you mean I can just install the 94136 in place of the precats, along with O2 sensors and call it good?

I was looking around and found the 24089s, which look like OEM replacements (length of pipe that comes with the precats and full cats), but to get both sides, it'd cost $700....

 

Yes the 94136 cats will be perfect one for each side. I am in mesa and running two maggie universal cats with no emissions issues for 3 yrs now. Way cheaper btw also. Granted I am not an '04 but I dont believe it will make a difference.

 

I'm running the 94136 cats but beware they make the truck very loud and I love it. It sounds like no cats but you are safe with emissions. No problems after 8 months with check engine lights or anything. They just make it sound way meaner.

 

Good deal, thanks guys. I just looked under it a second time and it turns out the second set of sensors is there. My bad.

Ill just have to take it to a muffler shop, since the last time it was done, the pipes were moved forward quite a bit, which will make it interesting to try to fit in the cats.

Otherwise, do you think a set of 91076s from Amazon would work? They do look like they're the same shape as the pre cats.

 

Yes, resurrecting a very old thread here...

What's the inlet/outlet diameter of the 94136? i.e. Did it match the diameter of the pipe, or is it meant to slip over?

Backstory:
The truck now has 328-something k miles on it. The original transmission lasted until 327,400, at which point, I had a rebuilt installed. After about 800 miles on it, it started shifting/accelerating sluggishly. The transmission shop couldn't find anything wrong with it, but suggested that the catalytic converters could be plugged. I don't remember what the transmission shop actually installed last time (in 2013), but it ended up being a Magnaflow universal (neither the 94136 nor 91076s).

I'm going to take it back to the exhaust shop on Monday to have it properly diagnosed, but should it need cats, I'm curious about the pipe diameter. The exhaust shop quoted me for a Magnaflow 51355, which has a 2.25" inlet/outlet diameter (and is much more expensive at $250/ea compared to $132/ea for the 94136). Also, the hole for the O2 sensors is located in the middle of the 51355 rather than towards the rear like on the current cats. Looking at the exhaust components in the catalog, the only diameter listed on any piece in the illustration is the Clamp after the Y pipe at 64mm or 2.51".

Taking the circumferences of the pipe and the inlet of the cat currently installed (I don't have a caliper), the pipe seems to be 2.15" in diameter (6.75"/ 3.1415), and the cat inlet calculated out to 2.6" in diameter (8.1875"/3.1415), but it's apparent they welded in the gap to make them fit. (This was done in Tucson, so that's no surprise.)

 

A very old thread and ironically the original responder right here 🤣

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Still got my truck too haha. From what I recall they are slip fit 2.5" in diameter. So stock piping is 2.5" OD. Magnaflow cat is 2.5" ID.

My engine light ended up just being the normal temp issue where you need to space the 2nd oxygen sensor a bit to trick the PCM from throwing the CEL. Still going from all these years later.

 

In case anyone else is looking up this information, and came across this with a websearch.......


AZBigIron needs a new exhaust shop. The truck has 2.5" pipes. Inlets and outlets on OEM exhaust parts are 2.5". MagnaFlow has an online catalog. You simply look up your truck, and it will give you the correct part. MagnaFlow will not sell you an exhaust component with the wrong sized pipe inlet/outlet. No competent shop would try to sell you the wrong part, or try to reduce your pipe size to make it fit.




So what? It's not as if anyone is posting anything new.