Hello guys, I'm shotgunning parts exhaust parts onto my 2001 pathfinder 3.5 V6 2001 (midyear), had bad fuel inj and was blowing alot of unused gas down exhaust. I'm mechanically inclined, aircraft mech on various turboprops and regional jets and larger Airbus320, but...no car lift nor garage. So after doing a top end job of new coil packs, fuel inj's, valve cover seals, spark plugs, new OEM idle air control valve and had an electronics shop repair the ECU, runs fine now; plus new suspension all around as the car has a solid frame and the engine has the power valve design change from the prior 2000 yr models..SO as I have all new 02 sensors and all cats, is there anyway to reach the FWD cats that are bolted onto the exhaust manifolds WITHOUT REMOVING THE ENGINE? Or the exhaust manifolds themselves...I've literally relied on all the posts i could find on this site for anything I've done so far and various manuals scrounging..other than working from underneath and removing the bottom cats: what is the method to get to the forward/upper cats...I'm on the fence as I have tools but considering the known rusty frozen exhaust hardware arena i'm on the fence to just take it to a muffler shop...
thanxs in advance for prior headaches and scraped knuckles of "wisdom"...

My Haynes Repair Manual has a very straight forward process to remove your exhaust manifolds and catalytic converters without removing the engine and without the use of a lift. A couple of jack stands and wheel chocks will be needed. It's a fairly short process but there is bound to be rusty exhaust system component bolts that will make this a long drawn out ordeal. A can of PB Blaster penetrating catalyst and a propane torch will be very helpful in getting those exhaust bolts removed, hopefully without breaking them. Spray the PB Blaster on all the exhaust component fasteners at least once so they can soak of several hours at least before taking a wrench to them. Just before wrenching them apart, heat up the fasteners with the propane torch and then spray them with PB Blaster again. Get the Haynes Manual for details. It's not a terribly complicated task but there are details regarding heat shields to remove (more PB Blaster), a coolant line on the right side that has to come off, and the power steering pump reservoir that must be moved but not removed. Starting in order of removal: Front exhaust pipes first, then the catalytic converters, and then the exhaust manifolds. I would give this job a three skinned knuckle rating.

Great to hear those cats are accessible from underneath, I'm referring to the front/forward cats that bolt directly onto the manifolds. I've seen vids of reaching the 02 sensors etc, but not specifically the upper most cats or "pre-cats", I do have a compressor and 3/8 drive impact gun. I was concerned with reaching the 6 bolts shown on the diagram/images of the upper pre-cats, from underneath. Also..regarding the early 2000-yrs maximas with the VQ35 motor having the infamous timing chain guides wear problems; any knowledge of the VQ35 motors in the 2001-ish Pathfinders have similar timing chain guide failures? My 2001.5 Pathy only has 154G miles and runs quiet with no odd sounds...thanx for the info

Oh and the Haynes Book I have doens't show/describe removing the cats..just a photo of what one is..I can see i'ts straight fwd, buuut as with anything there's a way to do things

The Haynes manual is a bit lacking on pics for this task of removing the cats from the manifolds but it does give some guidance. What I have seen on my '02 Pathfinder is that there are lots of things that need to be taken out of the way for access to the manifold to cat bolts as well as the manifold to block bolts. It is more complicated in detail to accomplish than pages of pics would show. Basically, there is a boat load of plumbing that needs to be moved out of the way. As for the timing chain, I have 220K miles on my Pathfinder and it stills runs smooth as well. I'm sure changing the oil every 3000 to 3500 miles has saved me from having to put too much repair work into this. I hope it stays that way because I no longer have garage to mess with that level of engine tear down and the days of time it would take me.

Agree, I"m not intending on removing the exh. manifolds, just the upper cats or ? pre-cats that bolt onto the exh. manifolds as I wasnt sure which way, from underneath or above, they were accessible. From what I understand from your previous post/reply is they are accessible from underneath. I've seen in nissan exhaust images there are six bolts on the upper cats and three on the lowers. Good to hear of the high mi. numbers on your path. I've seen near new appearing valve covers on other cars where the mechanic/owner literally changed his engine oil ea 1,000 mi., YEP!,.."so imagine the clean engine inside", as the soot that produced from the fuel injected gas/combustion process of which is like 1 micron in size (soot particles) cant be filtered out by the oil filters,..turn the oil black whereas the oil darkens as it breakdown over time...

I found something new, sort of: There's always been a lingering symptom of white smoke blowing from the exhaust, as I"d move the pathfinder across the yard..and a pool of white fluid build up in the tail pipe AND with the cat back exhaust removed the right side cat spits antifreeze coolant out, I saw it collect on the cardboard I have laying under the car etc..SO everyone is telling me w/ only 154,000 miles on the car "IT CANT BE" well ive the proof now etc..Can I remove the heads with the engine in the car? I've done similar work on older Accords and Preludes, and with reading these forums etc...it's basically a timing chain removal and the heads etc, post intake and exhaust mani's, I've ALSO recently replaced the entire intake plenums and gaskets to get to the fuel injectors..any advice or rough estimate on having a small shop do it and I already have the head gasket sets and head bolts on hand...

I'd like to add; I realize the reason for the various suggestions on older/other posts for removing the engine is due to removing the water pipe on the back of the engine (?) and simply ease of access to the rest of the engine such as the front for the timing chain and it's rear cover etc..and is it practical to do a timing chain job while the engine is in the car after removing the rad and fan?!