Exhaust Manifolds (1 Viewer)

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BMThiker

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So, I'm pricing replacements from dealership and they want nearly $800/side for just the manifold parts (I can do the labor). Anyone used a different option? I'm all ears.

Pretty sure my primary cats are toast and it's why I keep throwing P0171/0174 codes. I've only replaced my secondary O2 sensors at this point. Didn't seem worth replacing the primary sensors if the cats are bad anyways.
 
So, I'm pricing replacements from dealership and they want nearly $800/side for just the manifold parts (I can do the labor). Anyone used a different option? I'm all ears.

Pretty sure my primary cats are toast and it's why I keep throwing P0171/0174 codes. I've only replaced my secondary O2 sensors at this point. Didn't seem worth replacing the primary sensors if the cats are bad anyways.

That's a pretty reasonable price actually, from the dealer. The other option I could recommend that people have used is the Magnaflow version.

 
Lean codes are, afaik, being read and thrown by front sensors.
Not sure how cats could cause these codes.
Longer story here that started last summer when we drove to Cali. . . Initial cause of issues could have been bad gas, bad coil packs, clogged injectors, not acclimating to higher elevations, don't really know. Threw all the same codes then, and only now when driving long distances. Floating theory is bad coils/injectors were not burning off all fuel in system and dumped gas out manifolds, that cooked the cats. Cat inefficiency is causing the engine to run leaner? It's still throwing downstream O2 codes (0420/0430) after a good couple months without any - but those don't control fuel trim like the primaries do (it simply stopped the dash lights temporarily).
 
Do you have access to a scanner that shows fuel trim?
Longer story here that started last summer when we drove to Cali. . . Initial cause of issues could have been bad gas, bad coil packs, clogged injectors, not acclimating to higher elevations, don't really know. Threw all the same codes then, and only now when driving long distances. Floating theory is bad coils/injectors were not burning off all fuel in system and dumped gas out manifolds, that cooked the cats. Cat inefficiency is causing the engine to run leaner? It's still throwing downstream O2 codes (0420/0430) after a good couple months without any - but those don't control fuel trim like the primaries do (it simply stopped the dash lights temporarily).
 
Do you have access to a scanner that shows fuel trim?
I do have an app (with Toyota diagnostics add-on) that has a surprising number of metrics. I will see what I can do with it.
 
Went ahead and replaced these last weekend (280,700 miles on ODO). The first time these were replace was Aug 2012 at 121,000 miles on ODO. So, 160,000+ miles doesn't seem unreasonable for lifespan on these.

So far, no downstream O2 codes, which I had constantly. Prior to this, dash lights would typically trip on after only a few miles of resetting pending & permanent DCTs (mostly P0420/0430, on longer trips I would get an occasional upstream code P0173/0174). Crossing fingers this week goes without any dash lights.

Once my skids were removed, it wasn't a terrible job to do, except a bit of debris in the face. Took me about 3 hours. My exhaust system bolts were not seized and everything came apart fairly easy. Having small hands and arms is probably my saving grace, since there are some tight spots to get a socket or wrench on. The manifold bolts came off fairly easy. I think the hardest was the forward driver side because the alternator is in the way.

I was really expecting my primary cats to look a lot worse and a bunch of crap fall out of them. The passenger side did have a small blockage.
ExhManifolds (1).JPG


Driver side
ExhManifolds (2).JPG


Once cracked with a 12mm deep socket and longer drive handle, I got in there with a ratchet-wrench. That upstream O2 sensor harness (upper left behind down pipe) gave me more headache than any of the bolts did. I ended up using a very small screwdriver to wedge the cantilevered lock open and then gave it a good tug.
ExhManifolds (3).JPG


New manifolds, gaskets and a few replacement studs just in case.
ExhManifolds (5).JPG

Didn't need the studs. I also reused my primary O2 sensors. I wanted to see if in fact these really needed to be replaced.

After the job completion and a few highway miles, they blued in real nicely ;)
ExhManifolds (8).JPG

ExhManifolds (9).JPG
 
I am way overdue for a cat-back replacement of most of the exhaust system. My muffler looks like a cheese grater and spins on axis. After I installed the driver side manifold and got everything torqued down, the secondary cat now rests on the trans crossmember and rattles. All to be addressed soon. . .
 
Well... common ”problem” in Toyotas, these are tuned so strictly, a little increased emissions ans P0420 and P0430 shows up. The real emissions are still fine and smog test can be passed easily.

Solutions: O2 sensor spacers
1635185280847.jpeg


Or URD Dual Rear O2 Simulator.
 
What I could not shake were the P0174 & P0171 codes that would pop in addition to the P0420/P0430. I've run over 1200 miles since replacing the manifolds/cats and nary a code has popped. I'm not sure if the O2 spacers would have fixed it.
 

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