Just had a shop install my DT long headers, Y-pipe, 4 o2 spacers, and Gibson exhaust on my 05 V8. Sounds real loud! Unfortunately it smells super rich and threw a few P0430’s.

Think it’s because I have the upstream sensors with the spacers that the ECU isn’t adjusting correctly?

No spacers on the upstream O2 sensors! Take those off ASAP, I've heard cases of people accidentally putting them on the upstreams and it's causes issues due to things running too rich, aside from the fact that you're only supposed to put them on downstream to turn the CEL's off. Congrats on the entirely brand new exhaust though, I'm hoping to get the Y pipe and Gibson soon to pair with my LTs

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Exactly this, you're doing it wrong! Never space out an air/fuel ratio sensor. Only space out a catalyst efficiency sensor.

Ok, I was wrong. Took a look under the rig and they installed it correctly - only spacers on the second o2's. Everything looks right and clean under there.

Still smells really rich - I pulled the battery negative to reset the ECU again.

Talking a look at my long term fuel trim on banks 1-4 seem to all average around 0 - some up and down while driving but nothing major.

Any other ideas?

It's going to smell rich since you don't have cats!

X2

The catalyst performs a chemical reaction to unburned hydrocarbons (CO and oxides of nitrogen too) and changes them to other chemicals (ie water and CO2). Since you don’t have any cats, that is no longer happening on your truck....

Therefore raw (unburnt) fuel smell.

You ever smell a 60’s muscle car on cold start?

Sure but this just felt (smelt?) extreme - much more than just muscle car smell.

Ended up getting violent rattle at highway speeds this am as well - so back to the shop and have them take a look.

One of the front o2 sensors may have been damaged during removal or install, but if your fuel trims are showing close to zero, I’d not be inclined to think so.

Yeah, could be. What's a 'normal' long term fuel trim range? Mine average around 0 but do swing up to 4.75 or so. I assume banks 3 and 4 should always be 0 since we only have two?

Not sure about range for Toyota’s, but Audi can range between +14 to -14 on the LTFT before a CEL. I would figure Toyota would have tighter tolerances ( but I’m speculating with no real knowledge).

If it’s averaging around 0 that means the O2s are seeing a pretty correct air fuel ratio and no correction is needed long term.

Have you looked at STFT? Those should bounce back and forth neg and positive as it actively corrects. If one of the trims looks “lazy” it might be a failed O2.

Again I am probably speaking out of turn here. Hopefully someone with a lot more Toyota experience will chime in.

Oh I thought you meant it was running rich, not just smells rich. No cats anywhere and yes it'll stink. Mine didn't stink with stock y pipe but as soon as I took the rear cats off it'll sting your eyes. The P0430 means the spacers aren't enough to trick the catalyst efficiency monitor it took me 3 spacers and even then had an occasional fail with the y pipe 02 sensor locations. I ended up installing a universal URD 02 simulator and was able to remove all spacers with no worries now.

People still occasionally pop a code with the URD simulator as well. That is why I make the cat caps, they are 100% foolproof.

After a battery reset of the ECU and tightening down the exhaust bolts which seems to have rattled loose after 48 hours of use (and for some odd reason the drive shaft wasn't torqued correctly and I'm sure didn't impact the smell), the smell has gotten back to what I would expect without cats. I can see the short term and long term trims swinging up and down throughout a drive relatively in tandem, so I'm assuming the O2 sensors are working well.

If the smell really gets to me, I assume I can have an exhaust shop weld in a high flow cat downstream of the Y pipe, although that would be a shame with the Gibson. I know it's a hot topic for another thread but the 2K drone is F'ing annoying during long range freeway driving. Maybe that would change the resonance a little bit...

True, but luckily the universal one has some adjustments. So far on the recommended adjustments I've had no faults over a few thousand miles. The cat caps are for sure another great solution.