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I've been popping P0420 codes recently, and also experiencing a few stalls (no code). I've done a lot of searching and believe that my cat is not likely the problem. Reference this thread.
Per TSB. Some causes of P0420
Ã?â??Ã?· Malfunctioning ECT/CHT
Ã?â??Ã?· High fuel pressure
Ã?â??Ã?· Damaged exhaust manifold
Ã?â??Ã?· Cylinder misfiring
Ã?â??Ã?· HO2S wiring concerns (shorted or chafed, bent pins, etc.)
Ã?â??Ã?· Damaged exhaust system pipe
Ã?â??Ã?· Damaged muffler/tailpipe assembly
Ã?â??Ã?· Retarded spark timing
Damaged Catalytic Converter:
Ã?â??Ã?· Use of leaded fuel
Ã?â??Ã?· Oil contamination/consumption
Ã?â??Ã?· Silicone contamination (sealants/cleaners)
I'm determining a game plan and want some grey-hairs to advise. I think I'll first run down the list above, specifically focusing on the checking for high FP & bad ECT. If these check out ok, I plan on cleaning the IAC, as it's been 4 yrs and ~63K since it's been installed as new. If I get this far without finding it, then things get fuzzy as to what to check next. Any suggestions from here (or my plan in general)? PS. My plugs/wires a 6 months old, and I'm not experiencing any misfires, so I suspect my ignition & coil are ok.
96 Sport 2.0L - 190,XXX miles
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Originally posted by fdunford:
...I've done a lot of searching and believe that my cat is not likely the problem...
Actually, it most likely is the problem.
Check with your dealer to see if a reflash is available for your specifc model.
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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AFAIK, the PCM reflashing for P0420 is not available for 1996. You are looking at new precat or mileliminators (with gutting of the precat; I think MI does not have smog emissions testing).
"Always do the cheap and easy ones first."
1996 V6 ATX 96K miles
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Originally posted by projectSHO89:
Originally posted by fdunford:
...I've done a lot of searching and believe that my cat is not likely the problem...
Actually, it most likely is the problem.
Check with your dealer to see if a reflash is available for your specifc model.
Steve
that and the pcm reflash is for the duratec only I believe
at 181k if the O2 sensors haven't been changed maybe try that first but most likely the cat is cooked
- 95 Mystique LS - Zetec/5spd
- 99 Contour SeVT Sport - Duratec/5spd
Official NE-CEG Contour/Mustang Family
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Originally posted by Tony2005:
the PCM reflashing for P0420 is not available for 1996.
This would support what I found (or didn't find) via search.
Originally posted by Tony2005:
You are looking at new precat or mileliminators (with gutting of the precat
If it weren't for the stalls I started getting, I'd tend to be in agreement with you. I'm not convinced that a bad precat would cause stalls?
96 Sport 2.0L - 190,XXX miles
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Originally posted by BrApple:
at 181k if the O2 sensors haven't been changed maybe try that first
They were changed about a year and a half ago. I think I read in a search thread that the O2 tests were done before the cat eff test. If true, I suspect the sensors are ok.
96 Sport 2.0L - 190,XXX miles
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Originally posted by fdunford:
If it weren't for the stalls I started getting, I'd tend to be in agreement with you. I'm not convinced that a bad precat would cause stalls?
you do not have a precat on a zetec, they are only on the duratec. the cat is bolted right to the exhaust manifold
if you have no codes for the O2 sensors and the only code is for the cat then it is most likely the cat.
at least on the duratec the cat monitor sensor should read about .7 volts at idle, if you graph the O2 sensor with the cat monitor over top the cat monitor should follow behind the O2 sensor when driving, if it doesn't that means there is an issue with the cat. IIRC the closer to 1 volt you are the richer the system and I believe the closer to .1 volts you are is lean, but it might be just the opposite.
- 95 Mystique LS - Zetec/5spd
- 99 Contour SeVT Sport - Duratec/5spd
Official NE-CEG Contour/Mustang Family
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Originally posted by BrApple:
... the closer to 1 volt you are the richer the system and I believe the closer to .1 volts you are is lean, ...
You are correct.
"Always do the cheap and easy ones first."
1996 V6 ATX 96K miles
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Originally posted by BrApple:
if you have no codes for the O2 sensors and the only code is for the cat then it is most likely the cat.
I'm not challanging you, but am simply asking your opinion as to the stalls I started getting about the same time. Do you think a low cat eff would cause them?
Originally posted by BrApple:
if you graph the O2 sensor with the cat monitor over top the cat monitor should follow behind the O2 sensor when driving, if it doesn't that means there is an issue with the cat.
They show the graph in the TSB Figure 5 & 6. Looks hard to graph w/o the correct tools.
96 Sport 2.0L - 190,XXX miles
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if the cat has become plugged up then it could cause stalling
either way the pcm is telling you that there is something wrong with the cat so I really don't think that it would be much else
- 95 Mystique LS - Zetec/5spd
- 99 Contour SeVT Sport - Duratec/5spd
Official NE-CEG Contour/Mustang Family
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