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-   -   VX catalytic converter replacement (https://www.fuelly.com/forums/f10/vx-catalytic-converter-replacement-13072.html)

slogfilet 11-19-2010 07:26 AM

VX catalytic converter replacement
I'd like to remove my cat and examine it... I passed emissions, but my HC was pretty high. I also seem to be bogging a bit and losing power. In addition to my regular tune up, I'd like to take a look at the cat.


Is it easy to remove the cat? I thik it's just held on by some nuts and studs? Can I remove just the cat, or does the header have to come off too?

What do I look for when checking the cat? Is there a way to accurately guage its condition?

If it needs replacing, I assume OEM would be the easiest way to go... and also one of the most expensive. Is there a (quality) aftermarket cat that bolts right in?

EDIT: I'd also like to remove it so I can properly torque my block heater. I was lazy and just got it snug by reaching around the cat/header.

kamesama980 11-21-2010 05:06 PM

Re: VX catalytic converter replacement
unless it's physically damaged by something going through the engine and hitting it or overheating it by running rich and melting it, you cannot asses it's condition visually. since you say the engine is running anything but perfect, that points to another condition causing the rough running AND high HC (ie running rich).

I took a peek on your garage, I assume this is the VX and not the element? If so, what's the point of gutting the PCV valve? that could cause excess crankcase happyness to be burned in the engine resulting in dirty intake, IAC (depending on location of the PCV pipes) and high HC.

benfrogg 11-21-2010 08:39 PM

Re: VX catalytic converter replacement
Stock VX's come with a "gutted" PCV. There is a reason, to which I've forgotten, but it's required in this car. My PCV valve is simply a 90 degree elbow in the IM bracket. I assume he gutted a stock one because auto places don't sell the pcv without innards. Stealership only.

theholycow 11-22-2010 03:03 AM

Re: VX catalytic converter replacement
My Buick has just an elbow too. I've been puzzled about that. I had bought a PCV valve (which the parts stores had listed for my engine but none had in stock) then when I went to put it in there wasn't one there and it didn't fit. Maybe it wasn't originally equipped with a PCV valve.

slogfilet 11-22-2010 10:48 AM

Re: VX catalytic converter replacement
Yep, here's a thread on the VX's PCV valve:


As far as I can tell, it originally came with "gutless" valve.

benfrogg 11-22-2010 12:38 PM

Re: VX catalytic converter replacement
I will say, however, that kamesama980's point can be well taken anyway. When was the last time you cleaned the entire IM and TB? I know my TB gets nasty after 20-25k miles. If yours is particularly bad, that could elevate your HC's. It's basically un-metered HC's that are being sent through the IM. It's minor, I imagine, or at least it seems to me it would be a minor effect on a smog test, but it can't hurt to clean it if you haven't already done so.

slogfilet 11-22-2010 01:29 PM

Re: VX catalytic converter replacement
Sounds like a good idea!

Hi ho, hi ho, it's of to Helm's I go...

slogfilet 11-22-2010 01:31 PM

Re: VX catalytic converter replacement
But regardless, is it easy to remove the cat?

GasSavers_Erik 11-22-2010 02:12 PM

Re: VX catalytic converter replacement
You will likely twist off a few of the bolts because the corrosion will be too bad to loosen them- that is what usually happens to me anytime I work on an older car's exhaust system.

benfrogg 11-22-2010 02:15 PM

Re: VX catalytic converter replacement
I wouldn't say the cat is easy to remove. It depends on how rusty the nuts/bolts on the block side are and how bad the three bolts on the bottom of the cat. You'll pretty much have to cut those three with a sawzall or grinder/cut off disc (my preference). You'll have to replace them, the gasket that lives there, and the gasket at the top of the cat.

It isn't hard to remove either, i guess. It just isn't what I would call painless. Those nuts/bolts are pretty much cement on mine. As soon as you put a tool on em', they strip or break.

I read in your garage that your IACV was nasty. If that's the case, your Throttle body is gonna be worse. Make certain you back out (count the number of turns out and put it back in the same number of turns) the idle control screw. It's usually nasty in there.
You have to take off the throttle cable. Don't touch the adjustment allen screw/nut that is painted yellow. If you ever change it's setting (it adjusts how far the throttle plate closes) you'll hate yourself because you will NEVER get it back exactly right. I promise.
You'll need to buy a new gasket, most likely. (paper gasket) Don't try to use gasket maker or silicone. There are far too many nooks and crannies in there. I promise. (been there on both points)
You'll have to disconnect the coolant lines running through it. Thy only pee a little bit of coolant, so don't worry about it.
Take off the IACV again during the process. You need to clean the cavity between the IACV and throttle body.
You need a box of q-tips and THROTTLE BODY cleaner. DO NOT USE carburetor cleaner. It WILL eat gaskets at that location and further downstream. I only use carb cleaner on parts that are off of the car and have no gaskets and I can let them dry.
While you are at it, clean the IACV again. I usually set it on the bench and fill it with cleaner. Let is sit a while, then shake it with your hand covering the inlet/outlet.

If you are really up for a challenge, pull the whole intake manifold. You'll need another gasket to do this. Pull the injectors and buy gaskets for them too. Have them cleaned or look at my post on backyard mechanic cleaning of them. Take the IM to a shop with a kerosene parts cleaner and have them clean the inside of the IM. At the same time clean the EGR ports (search for it on this website). I had to drill and tap mine for later cleaning. I put four small and very short bolts with teflon tape on them to make it easy to repeat in a few thousand miles. Finally, remove the EGR valve and clean/test it for correct operation.

If it was me in your shoes, I'd start with the throttle body/IACV and make plans for cleaning the rest later.


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