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Old 07-22-2008, 10:42 PM   #1
dawnnewsome3
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Question Bad catalytic converter ?

I'm getting the typical smell of a bad catalytic converter , Low power , Stalling . My question is how hard is it to remove the manifolds to remove and change them , or would it work to leave them on and just remove the cat material from them and replace the second set , of that is what they are . I have access to a Hilti drill that will remove any material as it drill , would this even be worth trying . I don't know to much about these engines and I see no way to get to the manifols bolts from the top . And suggestions . This is a all stock engine except a M's K&N filter and dual exhaust from the rear back .Thanks for any help .
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Old 07-27-2008, 11:14 AM   #2
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Re: Bad catalytic converter ?

First off, ditch the K&N filter and restore the stock OEM CAI and filter as the oil from the K&N is known to degrade the MAF sensor to failure. A cone filter will actually rob you of power in the summer.

Secondly, the VH45DE has dual exhaust as it comes from the factory with very low restriction.

The Nissan catalytic convertors are very robust (why they are frequently stolen for their high platinum content) so seldom fail without abuse like running too long with a failed O2 sensor or non Tier 1 Premium fuel.

How about posting a maintenance history? Or got to Infiniti Onlin Mechanic Forum on www.nicoclub.com and post the same information?
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Old 07-27-2008, 02:32 PM   #3
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Re: Bad catalytic converter ?

Thanks for the reply , I bought the car from a person at the local bank and she let her daughter drive it . After reading up on the Three Way Catalyst Converter system I found out running low octane can cause the converters to overheat and fail and I know for a fact she always put the cheapest stuff she could in it . I don't Drive it much and I just recently started noticing the noticable smell of a bad cat . So I have decieded instead to replace all , I already have the motor set up on a motor holder that keeps it in place as I have removed the front subframe so I can remove the manifolds from the bottom . According to the diagnostic test of the heated oxygen sensor monitor all read OK , No Fail ?
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Old 07-28-2008, 04:27 PM   #4
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Re: Bad catalytic converter ?

Quote:
Originally Posted by dawnnewsome3
I found out running low octane can cause the converters to overheat and fail and I know for a fact she always put the cheapest stuff she could in it . I don't Drive it much and I just recently started noticing the noticable smell of a bad cat. I already have the motor set up on a motor holder that keeps it in place as I have removed the front subframe so I can remove the manifolds from the bottom .
Do refill with a Tier 1 premium and use some BG44K or the Redline SI1 injection cleaner in a few tanks. Replace the fuel filter first.

While the engine is suspended, do replace the two front motor mounts, the 3rd motor (transmission) mount and the associated exhaust hangars.

Hope you are not replacing all the catalysts without confirming they have failed. OEM is expensive as they last 350K+ miles if not abused. 3rd party replacements are lucky if they last 2 years. Be very careful.
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Old 07-28-2008, 10:31 PM   #5
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Re: Bad catalytic converter ?

Great advice thanks , I also noticed bad steering rack boot so I plan on fixing those also . I did run the Engine with the rear cats and pipes off and the first stage one's smelled fine , a friend suggested running a back pressure test on the other cats also to check for restrictions does this sound right , After working at a GM dealership you get in a bad habit of just replacing things instead of doing any real thorough testing .
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Old 07-28-2008, 10:45 PM   #6
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Re: Bad catalytic converter ?

Quote:
Originally Posted by dawnnewsome3
I did run the Engine with the rear cats and pipes off and the first stage one's smelled fine , a friend suggested running a back pressure test on the other cats also to check for restrictions does this sound right , After working at a GM dealership you get in a bad habit of just replacing things instead of doing any real thorough testing .
Yes, pressure checking is the way to go.

Be sure to flush all fluids and change all filters for a baseline. Check steering rack bushings, anti-sway bar bushings and links, and upper links per the FSM. I am sure you know how to check ball joints.

Extracting the R134a and lubricant, replacing the drier, and refilling per FSM is good too if you have the technology and expertise. Adding a B&M 70268 or 70264 ATF cooler is highly recommended for longer ATF life. www.summitracing.com

Call Infiniti of Scottsdale for OEM parts. Great service and you will save a ton or at least a little if you get trade discount from dealer as most charge over recommended list.

www.infinitipartsusa.com
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Last edited by maxnix; 07-29-2008 at 12:27 AM.
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Old 07-29-2008, 08:22 PM   #7
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Re: Bad catalytic converter ?

Thank you for all the help , I still have all access to the Chevrolet Dealership I worked at as my father is still the service manager so My car is there now on a lift and all the equipment I need is there to do about any thing as they work on other car than GM vehicle's as they service many different tradein's . Thanks for putting me on the right path . Your knowledge is most welcome . Another quick question about the rear suframe bushing , can you lower it enough to replace them or does it need to be dismantaled , Two have play in them and I think that is what is wearing the rear tire's out . The tire's wore nice and even and I have new one's but at the price of 19" tire's I want it fixed and alined before mounting they , Thanks Again .
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Old 07-30-2008, 09:48 PM   #8
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Re: Bad catalytic converter ?

Quote:
Originally Posted by dawnnewsome3
Another quick question about the rear suframe bushing , can you lower it enough to replace them or does it need to be dismantaled , Two have play in them and I think that is what is wearing the rear tire's out . The tire's wore nice and even and I have new one's but at the price of 19" tire's I want it fixed and alined before mounting they , Thanks Again .
If rear subframe bushings are leaking, you need to drop the frame and replace them after burning or pressing them out. If NVH is not a concern, you can use Z32 polyurethane (I can search for which energy suspension ones later or call them yourself), or order a new rear subframe from Joe ( www.infinitipartsusa.com ) as the bushings themselves are not known to be available.

Be sure you read the FSM before starting anything and that there is a access for any help you have (make them consult it before wrenching).

http://www.nicoclub.com/FSM/Q45/

I really recommend against 19" unless you exceed the OEM specified diameter of 26.1" say 26.7". It's tough to get strong enough tires with sufficient load capacity (minimum 95) required. XL rated top tier tires will work and be load rated 98-100, but off or secondary brand ones will not last long. Be sure all the rubber in the suspension is up to as new snuff. New Tokico blue shocks might be good also. Important for the wheels to be light and strong as even forged wheels will be adding unsprung rotational mass. This will decrease your car's ride comfort and dynamic performance.

Checking driveshaft balance might be worthwhile if you have the equipment.

Ohm test your injectors and KS and replace the KS harness if you replace them.

If it is a 1990 - 1993 you must remove the front timing covers and verify the newer metal backed timing chain guides are installed. If they are the old type, you should replace them and the tensioners and account for all pieces or be prepared drop the oil pan to retrieve the rest of it so it doesn't clog the oil pickup. The latter is extremely close to the bottom of the sump, so it is also worthwhile to inspect the pan bottom for any dents on the flat bottom as high RPM oil starvation can ruin your engine.
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Old 08-11-2008, 09:05 PM   #9
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Re: Bad catalytic converter ?

Thanks , It is a 1994 and the wheels are 19x8 Tenzo R Pysco with a 235-35-19 General / Exclaim UHP Tire , replaced rear cats and O2 sensors , plugs , and valve cover gaskets as ther was oil in the spark plug tube causing a bad connection . Cleaned the MAF sensor , the K&N filter I'm running is a dry one with a filter sock on it and it is seperated from heat from the engine by a heat shield as for the rear bushings I'll fix later . It is running great now I think the plugs in oil had a lot to do with it . Thanks for the help .
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Old 08-11-2008, 10:03 PM   #10
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Bad tire size!

Quote:
Originally Posted by dawnnewsome3
235-35-19 General / Exclaim UHP Tire.
91 is way below OEM minimum 95 load rating. Not a good thing and safety and handling are seriously compromised. You really need to think about 255/35 to meet that specification, although a 9" wide wheel is what is required, but 8.5" will work. +35mm offset might work as it does in 18".

Whatever you do, don't speed as an overloaded tire negates the speed rating.

For an experiment sometime, open the K&N and an OEM and compare the total filter medai area. Of course, that doesn't account for the filter media's effectiveness. Most don't beat OEM but rather allow larger chunks of contaminants in pursuit of added horsepower claims, which is horsefeathers in reality.

Few understand that the OEM CAI inlet is located in a high pressure area.
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Old 08-18-2008, 09:53 PM   #11
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Re: Bad catalytic converter ?

Thanks for the advice , and yes the oem air box does snake down to cooler unristricted air under the bumper where the air is much cooler , one question do you think the oem box would work with out all the baffling that lowers the intake resonant noise because this was removed them I got the car. I hate to change the wheels as I have a chunk of money in them as they are no longer made in 19" unless I could sell them and use the money for a better set .
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Old 08-20-2008, 04:52 PM   #12
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Re: Bad catalytic converter ?

Well, realize that the baffles are to prevent water intrusion and that there are also resonating chambers tuned to particular frequencies to produce a harmonic resonance boost to the intake charge at particular rpms. This is why almost all after market tuner intakes do little or usually impede engine performance. The VH45DE in particular is free breathing and exhausting with low restriction true dual exhausts. Total power loss vs. open system is about 3%, tough to improve upon without a major comprise of intake filtering or exahust noise and vibration.

Just be real careful with your tires, and personally I wouldn't go over 80 mph, especially in summer. You probably do have legal recourse to the shop and probabably some leverage with them for installing such under specification tires.
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