98 zj 4.0 high flow catalytic converter - JeepForum.com
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post #1 of 21 Old 02-14-2020, 11:40 AM Thread Starter
Gregory98zj
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98 zj 4.0 high flow catalytic converter

hey I need to know if a 400 hole high flow cat will throw my zj into limp mode.my old converter is getting red hot and needs replaced.

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post #2 of 21 Old 02-14-2020, 01:01 PM
jtec
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A 1998 zj 4.0l And you have a catalytic converter problem.
The Converter being red hot suggests there is excess fuel dumping into it, or less likely a seriously blocked exhaust.

A 1998 is a OBDII system, I would scan for codes, post ALL codes.
The cat is being damaged by a issue and you should correct the problem before it damages the new cat.
Tell us if you have access to a scanner to look at live data ECT, FUel trims, o2 sensor voltages.

When I see the price of OEM I think aftermarket.
When I see the quality of aftermarket I think OEM.
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post #3 of 21 Old 02-14-2020, 01:10 PM Thread Starter
Gregory98zj
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I've been using zinc additives in my oil for 3 years now and it's the cause of the clogged cat.
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post #4 of 21 Old 02-14-2020, 01:11 PM
zjosh93
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Yeah, a red hot cat is working, it just won't be working for very long. Replacing that cat is just going to result in a second melted cat.
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post #5 of 21 Old 02-14-2020, 01:13 PM Thread Starter
Gregory98zj
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I go threw this about every 3 yrs.it takes that long to clog one with oil addative (ZINC).
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post #6 of 21 Old 02-14-2020, 01:40 PM
zjosh93
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In that case. Are you looking at the standard Magnaflow ceramic matrix high flow cats or one of the metal matrix race cats? The Magnaflow won't set the catalyst efficiency code. The metal matrix ones might but you should be able to get around it with a O2 sensor spacer.

How much zinc are you running and how much oil do you burn? I exclusively use the diesel oil with more zinc and my cat is still good after 5 years (Magnaflow 3" high flow).
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post #7 of 21 Old 02-14-2020, 01:52 PM
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Quote:
Originally Posted by jtec View Post
A 1998 zj 4.0l And you have a catalytic converter problem.
The Converter being red hot suggests there is excess fuel dumping into it, or less likely a seriously blocked exhaust.

A 1998 is a OBDII system, I would scan for codes, post ALL codes.
The cat is being damaged by a issue and you should correct the problem before it damages the new cat.
Tell us if you have access to a scanner to look at live data ECT, FUel trims, o2 sensor voltages.

This.

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2002 Dakota aka Winnie aka Mad Max
1996 Grand Cherokee aka Puddles aka Pikey Life
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Originally Posted by kg6mov View Post
The 4.0 is dumb old tractor motor, itís too stupid to know itís supposed to die.
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post #8 of 21 Old 02-14-2020, 02:00 PM Thread Starter
Gregory98zj
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ok just pulled codes with friends obd11.got nothing.i use 1 tbs for every quart, so that 7 tbs of zinc.
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post #9 of 21 Old 02-14-2020, 02:02 PM Thread Starter
Gregory98zj
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my motor has 65000 original miles on it app I use 0 that burn no oil between changes.i was looking at another type of cat than a magnaflow.
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post #10 of 21 Old 02-14-2020, 02:04 PM Thread Starter
Gregory98zj
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magna flow. looking at the 2.25" Thunderbolt Catalytic Converter High Flow T409 Stainless Steel Rear O2 Nut
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post #11 of 21 Old 02-14-2020, 02:53 PM
Mr. Puddles
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Originally Posted by Gregory98zj View Post
ok just pulled codes with friends obd11.got nothing.i
Ok will that scanner pull live data or only codes?

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2002 Dakota aka Winnie aka Mad Max
1996 Grand Cherokee aka Puddles aka Pikey Life
Quote:
Originally Posted by kg6mov View Post
The 4.0 is dumb old tractor motor, itís too stupid to know itís supposed to die.
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post #12 of 21 Old 02-14-2020, 02:56 PM
Mr. Puddles
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Unless you are burning excessive amounts of oil Id say thats not it. What kind of mpg are you getting? Are you sure there is nothing in the exhaust and the pipe is not damaged?

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2002 Dakota aka Winnie aka Mad Max
1996 Grand Cherokee aka Puddles aka Pikey Life
Quote:
Originally Posted by kg6mov View Post
The 4.0 is dumb old tractor motor, itís too stupid to know itís supposed to die.
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post #13 of 21 Old 02-14-2020, 03:17 PM
zjosh93
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Quote:
Originally Posted by Gregory98zj View Post
magna flow. looking at the 2.25" Thunderbolt Catalytic Converter High Flow T409 Stainless Steel Rear O2 Nut
That's a ceramic matrix so it shouldn't trigger a catalyst code. In any case an O2 spacer almost always fixes it.

What zinc additive are you using? If you aren't burning much oil it shouldn't be poisoning your cats. Besides when a cat dies that way they typically just go cold not overheat. I'm just wondering if your getting into the too much zinc side of things.

Edit: If you want flow you can also just use a bigger cat. More flow area = less restriction. I put a 3" cat on my 93 and it blew through emissions here just fine.
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post #14 of 21 Old 02-14-2020, 03:52 PM Thread Starter
Gregory98zj
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no it will only pull codes.im was getting around 19 to 20 mpg.now about 15.
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post #15 of 21 Old 02-14-2020, 03:54 PM Thread Starter
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I only use 1 tbs of Lucas engine break in oil addative which is zinc or zddp.
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