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1998 Crimson Pearl STS 'W'
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266 Posts
Discussion Starter · #1 ·
I ask because my local fuel stop had their forecourt ripped up and the nearest one i could use was the dreaded BP,i dropped half a tank in and set out on a 20 mile web clearing blast,the car was faultless on the outbound journey with good accel/top speed but on the way home it started to ever so slightly pull back and seemed to struggle pulling anything above 80mph.
Once home i pulled the codes and have the..

P0420 'Catalyst system efficiency' current.
SES light never appeared.

I've done the WOT trick and nothing from the tailpipe and every other aspect of the car is 100%,good idle,temp at 12 always,no vac leaks, so my only thought is the BP fuel i pumped in.I cleared the code that night and took it for another run,same thing happened as above and the code returned.

Whats your views on this guy's..bad gas or bad cat.
Thanks.
 

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Administrator
2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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73,446 Posts
Your car has, in addition to an O2 sensor in each exhaust manifold, a pre- and post-cat O2 sensor. Those compare what went in to what comes out and that calculates cat "efficiency", so something's wrong.

Can you get Chevron TECHRON over there ??? If so, before you go replacing the cat, dump a 20 oz. jug into a tank of 93 octane and hit the motorway. See if that clears the problem. If it doesn't, then check the two O2 sensor pigtail connectors for integrity. Plugs, coils, wires all good ?

What options, other than BP, do you have for gasolines ?
 

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1998 Crimson Pearl STS 'W'
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266 Posts
Discussion Starter · #3 ·
What options, other than BP, do you have for gasolines ?
Hi Sub,
Not many to choose from..BP,shell and esso where i live,i usually use Esso 98 RON.
No chevron over here also,plugs and wires changed by previous owner at 85k (now at 93k) with OEM parts but you mentioned the coils which i never thought of,is it possible for these to be the problem once operating temp has been reached,i had a Austin mini that would run great until the coil started overheating and made it run like a bag of hammers.I'll get it up on the ramp to check those O2 sensor pigtails,if it is the cat on its way out ROCKAUTO is my only source for a new item,they sell a few so if possible could you look over their list and recommend one,if its no trouble of course.
Thanks again.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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73,446 Posts
You might remove the coils and ICM and clean the coil-ICM contacts as well as the ICM-engine ground wire terminals. If the miss just started the plug wire-coil connections are proper, but important. Each coil tower feeds a specific cylinder of the pair.

Shell is designated as a top tier fuel here - I wonder if it's blended with TECHRON there........I ran ESSO in my 327 Chevelle in Naples in the late 60's and had to decarbonise every 6 months !
 

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1998 Crimson Pearl STS 'W'
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266 Posts
Discussion Starter · #5 ·
I'll take a look tomorrow sub,also thanks for the info on SHELL/ESSO,gonna do some reading on both for comparison...:thumbsup:
 

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1998 Crimson Pearl STS 'W'
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266 Posts
Discussion Starter · #6 ·
Well i think i found my problem today.
This CAT is not stock,can anyone confirm..?


 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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73,446 Posts
Different years, but that looks nothing like my stock cat.

Also, an observation - I thought the 1999 had a pre- and post-cat O2 sensor. From the pics it looks like you have only 3 sensors: the manifold units and the post-cat, similar to mine. The resonator is the same as my old original, though, and the long exhaust pipe is the same - 1998 and earlier had a very different pipe route.
 

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1998 Crimson Pearl STS 'W'
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266 Posts
Discussion Starter · #8 ·
Your right on the O2 sensors sub,only 3 on this car that i seen today,now i'm 60% certain this CAT is the problem,would the original have bolted up both sides or like it is now bolted/welded...Just wondering what route to go down.

OEM CAT
AFTERMARKET
DE-CAT WITH SPARK PLUG ANTI- FOULERS :hmm:
 

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Super Moderator
2010 DTS
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88,148 Posts
Sub, I think by '99 they had already dropped the pre-CAT sensor. I know my '97 had 4, but if my memory has not failed me, I am pretty sure my daughters '99 only had 3, so I'm guessing the change was in '98 or '99.
 

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'98 STS (RIP @ 206,xxx miles)
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4,854 Posts
Different years, but that looks nothing like my stock cat.

Also, an observation - I thought the 1999 had a pre- and post-cat O2 sensor. From the pics it looks like you have only 3 sensors: the manifold units and the post-cat, similar to mine. The resonator is the same as my old original, though, and the long exhaust pipe is the same - 1998 and earlier had a very different pipe route.
Just to clarify - the Seville chassis redesign took place for the 1998 model and was essentialy unchanged through 2004 with the exception of the availability of magneride shocks & struts. The '98+ chassis is significantly different from '97 and earlier models which makes me cringe when I read owners/drivers of '97 models trying to assist with questions that pertain to '98+ models (but that's a personal problem).

As to the O2 sensors. The change from four to three O2 sensors took place during the 1998 model year for all Devilles, Eldos, and Sevilles.

Anyone with a 1998 Service Manual will see two different sensor schematic diagrams in the Engine Controls section with a note that says the four sensor diagram applies to early production and the three sensor diagram is for later production. My '98 has a build date of February and my car has three O2 sensors.
 

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1998 Crimson Pearl STS 'W'
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266 Posts
Discussion Starter · #11 ·
Can anyone recommend a cost effective replacement,might as well replace the resonator with a lighter item when i get round to it also.
 

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1999 Eldorado 2000 Jeep TJ 2000 Ford SD 4X4 Diesel crew cab
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372 Posts
My 1999 Eldo only uses 3 sensors. Just put a cat on it last year because the old one was rattleing I replaced it with a OEM unit and no problems.
 

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1998 Crimson Pearl STS 'W'
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266 Posts
Discussion Starter · #13 ·
My 1999 Eldo only uses 3 sensors. Just put a cat on it last year because the old one was rattleing I replaced it with a OEM unit and no problems.
I'd like to use OEM but Cadillac parts suppliers in the UK dont exist..lol,i'd use rockauto for the next best though.
 

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2000 Cadillac STS
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133 Posts
Hold the bus, been there, done that. I think the rockauto piece was an converter marked as a direct fit from the eastern company. It fits, yes, but does it work efficiently enough for an ODBII vehicle, NO. The same code 420 will appear shortly after. After a couple hours of research, I found this model 46006:
http://www.magnaflow.com/02catalytic_converters/02product/universalCARB/460.asp
It's CARB certified(one of the highest standards in the USA) and has been on my '00sts for >35k miles and 3yrs. w/o any issues, codes or smells. Google it for the best price in your area and have someone weld it up for ya. Make sure the pipe is 2.5" in and out.
 

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2002.5 F55 CORSA STS, 2014 Explorer XLT FWD
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Hold the bus, been there, done that. I think the rockauto piece was an converter marked as a direct fit from the eastern company. It fits, yes, but does it work efficiently enough for an ODBII vehicle, NO. The same code 420 will appear shortly after. After a couple hours of research, I found this model 46006:
http://www.magnaflow.com/02catalytic_converters/02product/universalCARB/460.asp
It's CARB certified(one of the highest standards in the USA) and has been on my '00sts for >35k miles and 3yrs. w/o any issues, codes or smells. Google it for the best price in your area and have someone weld it up for ya. Make sure the pipe is 2.5" in and out.
He's in Great Britain. Some aftermarket parts house will have to export the converter to him.
 

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1997 Cadillac STS (BOSE w/AUX In, Massage Seats, URPAS, "Z")
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6,405 Posts
There is no converter like the OEM converter. Unfortunately the OEM may be discontinued by now even for the '99 cars. I also noticed that in Europe a '99 car is actually build in '98, not that it matters in this situation, the cat is the same. Also my '97 has only 3 O2 sensors, one in each manifold and one post cat. Mechanically there is no much difference between the '97 and '99 cars, very minor details in the engine compartment some of the components have different location. Other than the body, the suspension and the electronic modules, everything else is the same as the older models. And even the parts that are not the same are same idea just slightly redesigned.
That Cat (if you can call it so) is by far the worst aftermarket patch I have ever seen.
I searched high and low for a OEM cat for my car, they were discontinued and even $1000 won't get me one. Eventually I found one in New Jersey forgotten in the back room of some dealership (was ordered years before and customer change his mind - lucky me). Even so it was from a '99 Eldorado not a '97 Seville. Although is not the same P# I have enough experience to know that the parts are basically the same. I was about to buy a used OEM cat, aftermarket was my very LAST option.
 

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2018 Camaro 2SS/NPP/F55/AQJ, Sold: 2015 Camaro, 2006 STS (EXP) 1997 Seville STS (EXP)
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448 Posts
Also my '97 has only 3 O2 sensors, one in each manifold and one post cat.
...hmmm...sure? ;)

...because...

...have a look to the 1997 FSM (book 2 of 2)...page 6-789 and 6-693...

...it says you should have 4 oxygen sensors....

manifolds:
1 front (Bank 2 Sensor 1)
1 rear (Bank 1 Sensor 1)
and:
1 pre-converter (Bank 1 Sensor 2)
1 post-converter (Bank 1 Sensor 3)
 

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2000 Cadillac STS
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133 Posts
There is no converter like the OEM converter.
That's right, most converters last longer before they set a 420 code at <100k miles.

That Cat (if you can call it so) is by far the worst aftermarket patch I have ever seen.
Evidently you negleted to read the link that was provided. :bigroll: or have any real world experience w/the model quoted.

Although is not the same P# I have enough experience to know that the parts are basically the same.
There is no way to tell the content of metallurgically deposited catalyst material internal to a converter by simply 'looking' at it. :tisk:

I was about to buy a used OEM cat, aftermarket was my very LAST option.
In the states it's a federal offense to put a used cat on a car that originally came with one.
 

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1997 Cadillac STS (BOSE w/AUX In, Massage Seats, URPAS, "Z")
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Evidently you neglected to read the link that was provided. or have any real world experience w/the model quoted.
Derone I don't really understand what you are referring to. I was talking about the "Cat" pictured few posts before.

There is no way to tell the content of metallurgically deposited catalyst material internal to a converter by simply 'looking' at it.
There is absolutely NO difference between a '99 Eldorado ETC engine and a '97 Seville STS. But absolutely NONE! Often suppliers change a small detail in the manufacturing process (like the paint) and that results in a new P# of basically the same part. With that being said you are right you can't tell the difference between the coating of the bricks just by looking at it. I did study both Cats (not with a microscope though) and I can tell that everything was IDENTICAL. It works happily in my car for over one year now, I have passed emissions with flying colors back in May last year.
In Canada as long as long as the car pass the emissions, no matter what you have in, is good to go for another 2 years.
Something tells me that a '99 brand new Cat is better than any aftermarket Cat by a distance so great that I can't even describe.
Took me about a year to locate a new OEM Cat, I ended up searching even in Germany, '97 is discontinued period. That's why I started looking in post '97 Eldorado (as is basically the same car, not many people realize it). There was the engine change in 2000, so after that yeah it kind of make sense for the Cat to be different, actually after '99 every year the Cat has a different P#, but there was no engine change between '00 and '02.
I was suggested by exhaust shops to weld two aftermarket Cats in serial if I am not comfortable with just one :) so imagine! I don't do monkey stuff in my car, NO WAY.
And in US it may be illegal to purchase a used Cat, but bet you any money a used Cat is better than a new aftermarket one (especially one that is like $130). Not to mention when I look under my car I see what it came from factory not something like ... well you can see it in that picture.

PontiacV8, last time I had the car on the lift was last weekend, I spent a good 3h replacing my inner tie rods, the ones that it says in the 2 years old bill were AcDelco, and look nothing like AcDelco :annoyed:. Back to the O2 sensor, I am pretty sure I haven't seen one, in fact I inspected the pre Cat flex pipe and Y pipe while I was there (still good). I can only see 1 O2 sensor (post Cat) the other 2 (manifolds) I have no way to see from under the car (or any position). But now I am curious, I will look specifically for it with the first occasion.
 
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