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Can someone tell me what these thing do? Do they like tell the computer that the cat's are there when they are not or what do they do? Thanks! 
hotrod90019
98 CSVT T-Red #4463
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Mileliminators trick the PCM by sending a signal to show that the pre-cats are working. If your pre-cats are bad or if you have headers, these will eliminate the P0420 Bank 1 and P0430 Bank 2 codes. Note that other codes not related to the pre-cats will still be sent to the PCM and light up the CEL.
"Always do the cheap and easy ones first."
1996 V6 ATX 96K miles
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I have a question about MIL and O2 sensors while we're on it...
Do normal O2 sensors have a variable signal that they send to the PCM? Like if the cats were doing one thing the O2 sensor would know that and the PCM would add more or less fuel?
The reason I ask is that my fuel mileage is crap and I wanted to replace my o2 sensor(s). If I use MIL eliminators instead will they act like brand me o2 sensors and help fuel mileage?
Brian W. -------------------- Black 1998 SE 5 speed - TOTALLED
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"Do normal O2 sensors have a variable signal that they send to the PCM? Like if the cats were doing one thing the O2 sensor would know that and the PCM would add more or less fuel?"
The upper O2 sensors (as well as other sensors but not lower O2 sensors *) will send signals to the PCM and have the PCM adjust the air/fuel mixture.
"The reason I ask is that my fuel mileage is crap and I wanted to replace my o2 sensor(s)."
If you have 100k miles or so on your upper O2 sensors, it might help.
"If I use MIL eliminators instead will they act like brand me o2 sensors and help fuel mileage?"
Mileliminators are for the lower O2 sensors only. In a previous thread, it was mentioned by two CEGers that the P0420 and P0430 codes do not affect fuel mileage. I do not agree * but do not have any technical documents to back up other than my personal experience with my fuel mileage being down when the CEL for P0420 was lighted (maybe there were also other issues or codes that I did not know about).
Last edited by Tony2005; 04/19/06 08:54 PM.
"Always do the cheap and easy ones first."
1996 V6 ATX 96K miles
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Tony,
Chicken... Egg... Chicken ... Egg ...
Which came first?
You're assuming that, in your case, that the cat codes caused the poor fuel economy.
More likely, the conditions that caused the poor fuel economy, ie, misfire, lazy upstream O2 sensor, or whatever caused an excessively rich exhaust, caused the cat to fail due to all the unburned fuel that was dumped into it. This then set the efficiency codes..
Makes more sense...doesn't it?
My 98 had recurring problems with the HO2S11 (P1131) several times, then misfires before 75K miles. Sure as can be, it got new cats under warranty as I've previously reported.
It is my conclusion that, in my case, the cat failure was accelerated by the rich conditions (P1131) and the unburned fuel from misfires.
hotrod,
I discussed MIL eliminators in detail a couple of months ago. See if you can dig up that tread in this forum.
Steve
98 Contour SE Sport 2.5 Duratec ATX The wifey's car
89 Taurus SHO - 246K miles
94 SHO ATX - 190K
1997 F-150 5.4L ATX - The Workhorse 150K.
ANY THREAD WITH "OMG" or "WTF" ETC IN THE TITLE WILL BE IGNORED!
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Originally posted by projectSHO89:
Tony,
Chicken... Egg... Chicken ... Egg ...
Which came first?
You're assuming that, in your case, that the cat codes caused the poor fuel economy.
More likely, the conditions that caused the poor fuel economy, ie, misfire, lazy upstream O2 sensor, or whatever caused an excessively rich exhaust, caused the cat to fail due to all the unburned fuel that was dumped into it. This then set the efficiency codes..
Makes more sense...doesn't it?..
Makes good sense.
Now, how about this? Cats failed (all things breakdown eventually) and plugged up causing the cats and engine not to work at full efficiency (due to increase in exhaust backpressure) i.e not enough vacuum in intake, with resulting loss in fuel economy and performance, causing CELs to come on.  (other codes too besides the P0420 or P0430)
Once again, chicken or the egg?
Yes, I will accept that the P0420 or P0430 will not put the PCM in limp mode (even though I don't have any documentation that says that). However, if you have the P0420 or P0430, chances are the car will run crappy eventually (when, after the CEL turns on, is anybody's guess).
"Always do the cheap and easy ones first."
1996 V6 ATX 96K miles
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P0420/P0430 codes are not necessarily coincidental to restricted flow.
Most dead cats flow just fine. It's just that the catalyst is contaminated/depleted and isn't performing any useful activity.
Plugged cats usually cause other problems, not efficiency codes.
Our 98 2.5 ran perfectly fine with high fuel efficiency with the efficiency codes set for two months while I was dinking with it and then waiting for the dealer to replace the pre-cats.
Remember, the downstream O2 sensors are only used for monitoring pollution controls, nothing else.
Steve
98 Contour SE Sport 2.5 Duratec ATX The wifey's car
89 Taurus SHO - 246K miles
94 SHO ATX - 190K
1997 F-150 5.4L ATX - The Workhorse 150K.
ANY THREAD WITH "OMG" or "WTF" ETC IN THE TITLE WILL BE IGNORED!
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Originally posted by projectSHO89:
...Plugged cats usually cause other problems, not efficiency codes.
...
Correct.
Here is something from the TSB (in our own backyard for documentation).
"P0420 - Catalyst System Efficiency Below Threshold (Bank 1) Indicates Bank 1 catalyst system efficiency is below the acceptable threshold.
�· Malfunctioning ECT/CHT
�· High fuel pressure
�· Damaged exhaust manifold
�· Cylinder misfiring
�· HO2S wiring concerns (shorted or chafed, bent pins, etc.)
�· Damaged exhaust system pipe
�· Damaged muffler/tailpipe assembly
�· Retarded spark timing
Damaged Catalytic Converter:
�· Use of leaded fuel
�· Oil contamination/consumption
�· Silicone contamination (sealants/cleaners)"
It appears, if the P0420/P0430 is caused by the top eight items, yes, the engine is already running rich or lean and the engine is sent to the limp mode (I am correct here). If it is caused by the bottom three items, it should not run in the limp mode until it causes other issues. So the P0420/P0430 codes does not necessarily cause the engine to run in a limp mode immediately all the time (you are correct here).
"Always do the cheap and easy ones first."
1996 V6 ATX 96K miles
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That's the code my car sent (P0420) will the mil eliminators fix my problem? If so how many do I need to buy.
Last edited by hotrod90019; 04/20/06 08:05 PM.
hotrod90019
98 CSVT T-Red #4463
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Originally posted by hotrod90019:
That's the code my car sent (P0420) will the mil eliminators fix my problem? If so how many do I need to buy.
it will since that is a cat efficience code, you need two, one for each bank and I do believe they are sold in pairs
- 95 Mystique LS - Zetec/5spd
- 99 Contour SeVT Sport - Duratec/5spd
Official NE-CEG Contour/Mustang Family
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