cat replacement

[Doc8404]

do converters have an expected life?
wondering if that's what's causing my hesitation. I have to replace the rest of my rusted out exhaust and rockauto has a direct replacement for $100

 

[Kestas]

Does your converter rattle when you shake it? If not, then you can leave it alone unless you need to replace it for emission purposes.

A clogged converter will result in loss of high-end performance such as poor acceleration, and it will limit your top speed. Explain your hesitation problem.

 

[Doc8404]

http://theoildrop.server101.com/forums/s...6b4i8h05j1h7ii5

this weekend, fuel filter #2 (gas tank replaced with junk yard tank, filter changed right before that) and O2 sensor.

 

[Kestas]

A clogged fuel filter will give the same symptoms as a restricted exhaust. Both will result in loss of high-end performance. Did you clean the tank before installing it in your car? A dirty fuel tank will keep clogging fuel fiters (been there).

 

[Doc8404]

no, i doubt the mechanic did...and he said it was varnished.

however, this problem occurred before the new tank, with a fresh filter.

 

[SteveD2]

Almost sounds like a faulty throttle position sensor...if your car has one??

Usually a cat will only affect WOT...it will act as if it is lagging power because they restrict airflow.

steved

 

[Doc8404]

no TPS on this...as far as I know...I thought the same thing until i (believe) read that the MFI doesn't have it.

 

[Quest]

a worn throttle shaft would give you similar hesitation symptoms due to air leak so make sure you check that part out before you go shopping for cat.

 

[Doc8404]

WTH is a throttle shaft?

 

[SteveD2]

Have you sprayed the intake down lately to remove carbon deposits in the throttle body??? My Outback gets a hesitation and that's where it stems from...

steved

 

[Doc8404]

cleaned the Maf and did that....very little carbon there (and little if any oil...even with my K&N)

 

[Quest]

Rob-

EFI gasoline engines typically comes with a throttle body (with a throttle plate (aka "butterfly" plate) that is linked by a shaft and rotated via your accelerator cable.

Just like old carb, a throttle body with a worn shaft will introduce additional air through the enlarged shaft gap and that would typically cause hesitation during acceleration, or leads to difficulty in maintaining proper idle rpm.

Check it out.

Q.

 

[Doc8404]

funny you say that, yesterday, the idle increased by 300 RPM's, driving me nuts.

 

[alreadygone]

Cat shell is stainless steel, will outlast your vehicle. You cannot poison with lead as all fuel is unleaded. Unless it rattles when bumped with palm (as mentioned already), or you are using guart of oil each tank of fuel, it's highly unlikely cat is your problem. They will cause power loss under load, getting progressively worse as load/speed increases, not hesitation.

Use the $100. to get professional to diagnose.

Bob

 

[JustinH]

You can get a universal cat on ebay for almost free, less than 20 bucks.

Get a highflow one while you are at it. Carsound makes a good one.

Unless you are in cali, then they have strict cat rules, you can't use alot of replacements.

 

[moribundman]

Not only CA has strict rules...

Anyway, a $20 cat is worth what? $5? How long will that last? Two weeks?

 

[Doc8404]

thanks to all.
bought a 12-range Analog multimeter (it just hit me that i should've bought a digital) and will figure out how to use it and troubleshoot.

 

[Kestas]

Quote:

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Cat shell is stainless steel, will outlast your vehicle....

---

Not always. But it should last at least through the federally mandated emission warranty (80K?). Depending on the manufacturer, cat shells are made of 409 stainless steel, one of the cheapest stainless steels out there. One of the unique problems with this steel is sensitization of the welds, where the welds can crack in a corrosive environment. One of the auto manufacturers paid our lab good money to study this.

The japanese use better steel (321) for their cats and exhaust systems.

 

[MarkC]

My cat in my Jeep is bad @ 130k. Luckily there's a recall and it's getting replaced free.
It rattled for a long time, and for a couple of days the exhaust seemed restricted, but lately, no noise, no power loss. Just waiting for the new one to arrive.

 

[eljefino]

You can have a cat that's fine, albeit rattling-- if you can even hear it-- one day. The next, a chip of the loose innards can slide to the rear opening and almost plug it. Then it's time for a new one.

In addition to the multimeter, a vacuum gauge will tell you if you have a restricted exhaust. If it goes down to zero inches when you're driving down the road with a light throttle, or if it slowly drops when you idle at 2000 RPMs, you have trouble.