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Z-Rod and clogged cats?

This is a discussion on Z-Rod and clogged cats? within the External Engine forums, part of the LSx Technical Help Section category; Not sure if this is the case, but I notice a little sputter at low rpm in all gears. Below ...

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    Senior Member Naaman's Avatar
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    Z-Rod and clogged cats?

    Not sure if this is the case, but I notice a little sputter at low rpm in all gears. Below 2000 rpm, if I press on the throttle more than just a teeny bit, I get a lag or a lugging effect until the revs cross the 2000 mark.

    I have considered that it might be a clogged up intake. I have installed a fresh paper filter. I sprayed MAF cleaner on the MAF, and I sprayed TB cleaner through the TB. The sputter stayed.

    I have also noticed that my fuel economy seems to be "mysteriously" getting incrementally worse. Nothing major, yet, but it's been perplexing me: every tank I seem to get about 1/8 mpg worse than the last tank.

    If it's not the intake, could it be the cats getting plugged up?

    I have no codes at this time. Also, the engine in my car is from an 01, but the PCM is a 98, so it would be looking for certain devices that are not there (and thus those codes have been tuned out).


    How would I know if the cats are plugged up (they have 118K miles on them besides the Z-rod oil being run in the engine).

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    Veteran 0rion's Avatar
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    clogged cats will do that....they'll also take some of the balls out of the car. Without going over everything and logging it it's hard to say that's exactly what your problem is but it's definitely on the table. Could also be a vacuum leak, O2's on the way out, misfire, ect ect. so it could be a few things but clogged cats would be included in that list.
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    Z-Rod and clogged cats?

    If you have an infrared temp gun check the temp at pipe going into cat and pipe coming out , temp should be higher at rear of cat . Also engine vacuum should be below normal if cats are plugging up .

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    Senior Member Naaman's Avatar
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    Quote Originally Posted by 0rion View Post
    clogged cats will do that....they'll also take some of the balls out of the car. Without going over everything and logging it it's hard to say that's exactly what your problem is but it's definitely on the table. Could also be a vacuum leak, O2's on the way out, misfire, ect ect. so it could be a few things but clogged cats would be included in that list.
    Yeah. After thinking about it some more, I've also added the fuel filter to the list of possibilities. I'll be taking my car to have the cat-back swapped out later this month and so will hopefully be able to have the cats inspected/checked/whatever.

    Quote Originally Posted by douglowden116 View Post
    If you have an infrared temp gun check the temp at pipe going into cat and pipe coming out , temp should be higher at rear of cat . Also engine vacuum should be below normal if cats are plugging up .
    Don't have a temp gun, but might look into getting one.
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    Member SuperSSguy's Avatar
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    Hey Naaman...noticed you said you sprayed cleaner through your throttle body? Anyone think maybe he should do a more thorough cleaning like maybe remove and clean it...I heard that sometimes that if the blades/butterfly gets gummed up enough the blade wont properly close/open correctly?...also I think the fuel filter would be the next easiest and cheapest thing to try next...It is one of the most forgotten about parts on most vehicles.Also wouldn't the car throw a code if the cats were clogging/clogged?

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    Veteran 0rion's Avatar
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    he says some codes have been turned off.....I'm guessing 420 and 430 would be 2 of those.

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    Senior Member Naaman's Avatar
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    Quote Originally Posted by SuperSSguy View Post
    Hey Naaman...noticed you said you sprayed cleaner through your throttle body? Anyone think maybe he should do a more thorough cleaning like maybe remove and clean it...I heard that sometimes that if the blades/butterfly gets gummed up enough the blade wont properly close/open correctly?...also I think the fuel filter would be the next easiest and cheapest thing to try next...It is one of the most forgotten about parts on most vehicles.Also wouldn't the car throw a code if the cats were clogging/clogged?
    When I took the MAF off, I was able to manually open the throttle and I got it pretty much all the way clean (didn't scrub the back side, obviously), but I opened it up while the engine was running and sprayed through there, as well as through the little idle hole.

    I didn't make this clear in the original post, but, the reason I suspected the oil is because it's my understanding that zinc was no longer used in OEM applications because it clogged up cats (though, FBJ says that he's never had that happen using high zinc oil in engines with cats--also, it seems like motor oil should only be getting into the cats if there is something else wrong, no?).

    Quote Originally Posted by 0rion View Post
    he says some codes have been turned off.....I'm guessing 420 and 430 would be 2 of those.
    I'm not sure which codes have been turned off. I know the SAI and EGR have been, but I'm still running stock manifolds, so I'll have to find out from my shop which codes he turned off.

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    Member SuperSSguy's Avatar
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    Naaman...I see that you have 118k on the cats...To me no where near being in the fail range as per normal wear and tear (according to statistics and averages but??) Obviously the Dealerships warranty is long gone....But just in case...If you do have to R/R them ,Dont forget that you may still have recourse under Federal Smog Warranty? Dont have my manual handy but If I remember correctly I think it was pretty substantial? Just something to keep in mind in case...Sorry im not really sure how to help with your problem other then to agree with others about testing the cats with a Temp/ meter (gun)...I read about this while at a garage ,The owners had a book from one of the cat makers all about this and other important cat info....also like was said earlier...If you cant remember the last time your fuel filter was changed I would definitely do that...doesn't cost that much,Is easy to do and wouldn't hurt to eliminate that anyway...Please keep us posted! Good Luck...

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    Senior Member Naaman's Avatar
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    Fuel filter has 24,000 miles on it.

    I will update when new info is available.

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