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Joined: May 2000
Posts: 2,127
Hard-core CEG'er
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Hard-core CEG'er
Joined: May 2000
Posts: 2,127 |
Hey, don't take my word for it, let's hear what our resident Ford Service Manager has to say about this... http://www.contour.org/ubbthreads/showthreaded.php?Cat=&Board=trouble&Number=422653&page=0&view=collapsed&sb=5&o=7&vc=1Originally posted by Big Jim:
This is usually not an oxygen sensor problem. This is usually a marginal or dead cat. Your emissions warranty may cover it. Your extended warranty probably does not.
Your car has four oxygen sensors. One on each bank before any cats, and one after the front cat on each bank. The oxygen sensor behind the cat is actually called a cat monitor. It tells how effeciently the cat is operating.
An oxygen sensor produces a small voltage in the presence of oxygen. 0 voltage is a lean reading. .9 volts is a rich reading. The oxygen sensor is constantly switching between 0 and .9 on a properly running engine. The cat tends to stabilize the oxygen sensor readings so the swing between rich and lean will be either much slower or nearly non existant from the cat monitor oxygen sensor if the cat is working properly. The PCM compares the front and rear oxygen sensor and screams "tilt" if the readings are switching nearly at the same speed, turns on the check engine light, and sets a code. The cat monitor system in the PCM does not run constantly. It is an intermittant test that is only done when certain conditions are met including that all other monitors have run and the the engine is well warmed up.
On California emission system cars, the cats are warranted for 7/70. On Federal emission system cars, the cats are warranted for 8/80.
With all that said, I have had that code set on my car from time to time and the cat seems to have restored itself. I have not had it on for at least a year. I have scanned the oxygen sensors and the cat monitor oxygen sensors and they are switching as expected, fast in front and very slow in rear. The cat has not been replaced. It may help that I clean the throttle body, intake manifold, combustion chambers, and injectors often and keep the ignition system and air filter is exception condition.
Let us know how things work out with this.
So again, if the D/S sensor is switching like the U/S, then the CAT isn't working right. However, like I said before, if the engine is running lean, then the D/S sensor will probably stay in the lean range.
FWIW,
TB
"Seems like our society is more interested in turning each successive generation into cookie-cutter wankers than anything else." -- Jato 8/24/2004
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Joined: Sep 2003
Posts: 2,725
Hard-core CEG\'er
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Hard-core CEG\'er
Joined: Sep 2003
Posts: 2,725 |
Okay I see what your saying now.
Well before he did the work Friday I asked him again if he was sure that sensor was bad, he said he was.
If it comes back I will tell him I want a refund since he replaced a part that didnt need to be.
The code came on on the 2nd, and hasnt came back yet......
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Joined: Nov 2002
Posts: 851
Veteran CEG\'er
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Veteran CEG\'er
Joined: Nov 2002
Posts: 851 |
Originally posted by BOFH:
So like I said about a week ago, you DON'T WANT the downstream sensor switching at the same rate as the upstream.
You know, I was thinking about this, and it's too bad that Ford decided to use a different connector on the upstream and downstream sensors.
If they hadn't, you could easily replace your upstream sensor with a new one, and then put that old worn-out oxygen sensor in the downstream.
As it is, you could cut 'n' splice the wires I guess..
Given that oxygen sensors start switching slower as they age, this MIGHT make it stop complaining about a marginal cat, and because you replaced the upstream sensor, it'll be more likely to pass emissions. Hey, a bonus!
Or you could just get some MIL eliminators, but I wonder if any of the emissions test stations know to look for them yet?
Last edited by brianl703; 02/08/04 09:17 PM.
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Joined: Sep 2003
Posts: 2,725
Hard-core CEG\'er
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Hard-core CEG\'er
Joined: Sep 2003
Posts: 2,725 |
We dont even have emissions test here. Good thing to, I know many friends whos cars would fail.
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Joined: Aug 2001
Posts: 4,639
Hard-core CEG'er
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Hard-core CEG'er
Joined: Aug 2001
Posts: 4,639 |
171 is lean bank 1, 174 is lean bank 2. if u have a zetec i believe it only has one bank.
also see some of the other idling trouble posts for more info on this.
Hugo AIM:omegazodiac
95 gl & 99 contour svt #1750/2760
my profile pics stuff for sale
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