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Old 12-24-2005, 19:01   #1 (permalink)
rottyguy70@yahoo.com
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92 f150 exhaust question

hey all, had to replace my entire exhaust system on my 92' f150 (inline
6). the old exhaust had an openning for the o2 in the front and
another opening for a line from what appears to be some emissions parts
(unsure what it is) right before the cat (it was a welded piece that
attached to a rubber line about 1" thick that run to the front of the
engine near the top). i bought a replacement exhaust system from
advanced auto that bolts in and hangs correctly but does not have this
extra openning for this line. anyone familiar with this engine can let
me know what the purpose of this line does (if i trace it up, it looks
like parts of it recircs the exhaust back to the engine and some
escapes to the exhaust). i'm having difficulty understanding why the
new system does not support this line and if it's really necessary. i
bought the car used in DC but wonder if this was an original california
car with some extra emissions required for that state (am currently in
DC).

thanks.

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Old 12-24-2005, 20:01   #2 (permalink)
Jim Warman
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Re: 92 f150 exhaust question

Sounds like the tube is for downstream air from the thermactor system. When
the motor is at operating temp, this air (from the "smog" pump) is delivered
to the exhaust manifolds but, when the cat is cold, the air is pumped to the
converer to help bring it to temp quicker.

When we get into some of these aftermarket parts, especially for older
vehicles, it can become a "one size fits all... or nearly all" thing. It
could also be the result of somone failing to read the footnotes in the
parts catalogue.

HTH


<rottyguy70@yahoo.com> wrote in message
news:1135475330.160211.195480@f14g2000cwb.googlegroups.com...
> hey all, had to replace my entire exhaust system on my 92' f150 (inline
> 6). the old exhaust had an openning for the o2 in the front and
> another opening for a line from what appears to be some emissions parts
> (unsure what it is) right before the cat (it was a welded piece that
> attached to a rubber line about 1" thick that run to the front of the
> engine near the top). i bought a replacement exhaust system from
> advanced auto that bolts in and hangs correctly but does not have this
> extra openning for this line. anyone familiar with this engine can let
> me know what the purpose of this line does (if i trace it up, it looks
> like parts of it recircs the exhaust back to the engine and some
> escapes to the exhaust). i'm having difficulty understanding why the
> new system does not support this line and if it's really necessary. i
> bought the car used in DC but wonder if this was an original california
> car with some extra emissions required for that state (am currently in
> DC).
>
> thanks.
>



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Old 12-24-2005, 23:01   #3 (permalink)
Shoe Salesman
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Posts: n/a
Re: 92 f150 exhaust question


"Jim Warman" <mechanic@telusplanet.net> wrote in message
news:oanrf.7041$AP5.5689@edtnps84...
> Sounds like the tube is for downstream air from the thermactor system.
> When the motor is at operating temp, this air (from the "smog" pump) is
> delivered to the exhaust manifolds but, when the cat is cold, the air is
> pumped to the converer to help bring it to temp quicker.


I think you got it backwards, can't pump air into the manifold above the O2
in closed loop, it would read too much O2. It will go upstream when cold,
then downstream when hot. Sounds like it could be a CA only thing too. I
think I would have a muffler shop weld the pipe on it, or better yet, get
the correct part.

>
> When we get into some of these aftermarket parts, especially for older
> vehicles, it can become a "one size fits all... or nearly all" thing. It
> could also be the result of somone failing to read the footnotes in the
> parts catalogue.
>
> HTH
>
>
> <rottyguy70@yahoo.com> wrote in message
> news:1135475330.160211.195480@f14g2000cwb.googlegroups.com...
>> hey all, had to replace my entire exhaust system on my 92' f150 (inline
>> 6). the old exhaust had an openning for the o2 in the front and
>> another opening for a line from what appears to be some emissions parts
>> (unsure what it is) right before the cat (it was a welded piece that
>> attached to a rubber line about 1" thick that run to the front of the
>> engine near the top). i bought a replacement exhaust system from
>> advanced auto that bolts in and hangs correctly but does not have this
>> extra openning for this line. anyone familiar with this engine can let
>> me know what the purpose of this line does (if i trace it up, it looks
>> like parts of it recircs the exhaust back to the engine and some
>> escapes to the exhaust). i'm having difficulty understanding why the
>> new system does not support this line and if it's really necessary. i
>> bought the car used in DC but wonder if this was an original california
>> car with some extra emissions required for that state (am currently in
>> DC).
>>
>> thanks.
>>

>
>



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Old 12-25-2005, 00:01   #4 (permalink)
Tom Adkins
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Posts: n/a
Re: 92 f150 exhaust question

Shoe Salesman wrote:


> I think you got it backwards, can't pump air into the manifold above the O2
> in closed loop, it would read too much O2. It will go upstream when cold,
> then downstream when hot. Sounds like it could be a CA only thing too. I
> think I would have a muffler shop weld the pipe on it, or better yet, get
> the correct part.
>




Nope Shoe,
Jim has it right. The air is diverted to the cats during warmup to help light off
the cats quicker, then diverted to the manifolds to help burn off unburned HCs before
the exhaust reaches the cats.
For a long time 3\4 ton and up trucks were exempt from some emissions regs.(It was
that way in the 70s, through at least much of the 80s and possibly very early 90s).
It's likely that his pipe was intended for an F-250 or better vehicle without the
Thermactor system. I've seen the 300CID\4.9L in F-250s many times, not sure about
heavier duty trucks. (Thus the melding of aftermarket part numbers)

Rott...
Take care of that motor in your truck and you will own it for quite a while. The
hose you are referring to was probably steel down to the cat originally. They tend to
rust off just above the converter. Someone probably "repaired" it with hose.(hopefully
silicone). To do it "right" you would have to have someone weld a nipple into it to
attach a replacement steel pipe to (Pipe is about $30). You could do the nipple and
existing hose also, but the hose usually burns off at the cat in a short while.

If you're in an area that doesn't do emissions testing, you could remove the
Thermactor pump and related plumbing, but on a 92 it would probably cause codes to be
set in the ECM and the EEC_IV system to default into "limp" mode. (Mr Warman can
likely elaborate on that if it's true, I don't remember).

On a personal note, it's a shame that Ford had to stop producing the 300\4.9. I'm told
that they couldn't make it meet emissions in later years. That motor was a real
workhorse. Given a choice between a 300 and a 302 (4.9 and 5.0L) in a pickup truck, I
would take the 300 hands down. (And I'm a big fan of V-8 Ford motors).
You could just about drag your house down the street for 200K miles, give the motor
a valve job, and drag it another 200K, with an F-150 equipped with a 300cid\4.9L six
and a 3 speed manual trans. That's stretching it a bit I know, but it conveys the
reliability and torque of that motor. They were tough little suckers with lots of
torque that would run for miles and miles..

Hope this helps, Tom Adkins
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Old 12-25-2005, 05:01   #5 (permalink)
rottyguy70@yahoo.com
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Posts: n/a
Re: 92 f150 exhaust question

hi all, thanks for the response.

the replacement cat does have a nipple that is sealed but is
significantly smaller then the metal tube from the thermactor (tom, it
did indeed rusted off as you said)-- like 1/4" to 1". would this
nipple suffice if i were able to find a converter or is it too small?

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Old 12-25-2005, 13:01   #6 (permalink)
Shoe Salesman
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Posts: n/a
Re: 92 f150 exhaust question


"Tom Adkins" <newton5@remove.comcast.net> wrote in message
news:hPadnbM-rdbooDPenZ2dnUVZ_tqdnZ2d@comcast.com...
> Shoe Salesman wrote:
>
>
>> I think you got it backwards, can't pump air into the manifold above the
>> O2 in closed loop, it would read too much O2. It will go upstream when
>> cold, then downstream when hot. Sounds like it could be a CA only thing
>> too. I think I would have a muffler shop weld the pipe on it, or better
>> yet, get the correct part.
>>

>
>
>
> Nope Shoe,
> Jim has it right. The air is diverted to the cats during warmup to help
> light off the cats quicker, then diverted to the manifolds to help burn
> off unburned HCs before the exhaust reaches the cats.


Ok, so, he said its a straight 6 right? So its got 1 manifold right? Its got
an O2 sensor in that manifold (or just below it). How can you pump air into
the manifold (when its warmed up) and not give the O2 false info?


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Old 12-25-2005, 13:01   #7 (permalink)
aarcuda69062
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Posts: n/a
Re: 92 f150 exhaust question

In article <9ICrf.7450$ka.1602@tornado.socal.rr.com>,
"Shoe Salesman" <someone@microsoft.com> wrote:

> "Tom Adkins" <newton5@remove.comcast.net> wrote in message
> news:hPadnbM-rdbooDPenZ2dnUVZ_tqdnZ2d@comcast.com...
> > Shoe Salesman wrote:
> >
> >
> >> I think you got it backwards, can't pump air into the manifold above the
> >> O2 in closed loop, it would read too much O2. It will go upstream when
> >> cold, then downstream when hot. Sounds like it could be a CA only thing
> >> too. I think I would have a muffler shop weld the pipe on it, or better
> >> yet, get the correct part.
> >>

> >
> >
> >
> > Nope Shoe,
> > Jim has it right. The air is diverted to the cats during warmup to help
> > light off the cats quicker, then diverted to the manifolds to help burn
> > off unburned HCs before the exhaust reaches the cats.

>
> Ok, so, he said its a straight 6 right? So its got 1 manifold right? Its got
> an O2 sensor in that manifold (or just below it). How can you pump air into
> the manifold (when its warmed up) and not give the O2 false info?


By programming the PCM to ignore O2 sensor signals under
conditions when air is being injected upstream.

Notice that in Jim and Tom's replies the absence of the word
'always.'
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Old 12-25-2005, 14:01   #8 (permalink)
Shoe Salesman
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Posts: n/a
Re: 92 f150 exhaust question


"aarcuda69062" <nonelson@sbcglobal.net> wrote in message
news:nonelson-5C139A.13525925122005@newsclstr02.news.prodigy.com...
> In article <9ICrf.7450$ka.1602@tornado.socal.rr.com>,
> "Shoe Salesman" <someone@microsoft.com> wrote:
>
>> "Tom Adkins" <newton5@remove.comcast.net> wrote in message
>> news:hPadnbM-rdbooDPenZ2dnUVZ_tqdnZ2d@comcast.com...
>> > Shoe Salesman wrote:
>> >
>> >
>> >> I think you got it backwards, can't pump air into the manifold above
>> >> the
>> >> O2 in closed loop, it would read too much O2. It will go upstream when
>> >> cold, then downstream when hot. Sounds like it could be a CA only
>> >> thing
>> >> too. I think I would have a muffler shop weld the pipe on it, or
>> >> better
>> >> yet, get the correct part.
>> >>
>> >
>> >
>> >
>> > Nope Shoe,
>> > Jim has it right. The air is diverted to the cats during warmup to
>> > help
>> > light off the cats quicker, then diverted to the manifolds to help burn
>> > off unburned HCs before the exhaust reaches the cats.

>>
>> Ok, so, he said its a straight 6 right? So its got 1 manifold right? Its
>> got
>> an O2 sensor in that manifold (or just below it). How can you pump air
>> into
>> the manifold (when its warmed up) and not give the O2 false info?

>
> By programming the PCM to ignore O2 sensor signals under
> conditions when air is being injected upstream.
>
> Notice that in Jim and Tom's replies the absence of the word
> 'always.'


So its downstream when cold then diverted to atmosphere when it reaches
norm operating temp, exept under certain conditions? What are those
conditions?


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Old 12-25-2005, 16:01   #9 (permalink)
aarcuda69062
Guest
 
Posts: n/a
Re: 92 f150 exhaust question

In article <H_Crf.6351$pE4.3438@tornado.socal.rr.com>,
"Shoe Salesman" <someone@microsoft.com> wrote:

> "aarcuda69062" <nonelson@sbcglobal.net> wrote in message
> news:nonelson-5C139A.13525925122005@newsclstr02.news.prodigy.com...
> > In article <9ICrf.7450$ka.1602@tornado.socal.rr.com>,
> > "Shoe Salesman" <someone@microsoft.com> wrote:
> >
> >> "Tom Adkins" <newton5@remove.comcast.net> wrote in message
> >> news:hPadnbM-rdbooDPenZ2dnUVZ_tqdnZ2d@comcast.com...
> >> > Shoe Salesman wrote:
> >> >
> >> >
> >> >> I think you got it backwards, can't pump air into the manifold above
> >> >> the
> >> >> O2 in closed loop, it would read too much O2. It will go upstream when
> >> >> cold, then downstream when hot. Sounds like it could be a CA only
> >> >> thing
> >> >> too. I think I would have a muffler shop weld the pipe on it, or
> >> >> better
> >> >> yet, get the correct part.
> >> >>
> >> >
> >> >
> >> >
> >> > Nope Shoe,
> >> > Jim has it right. The air is diverted to the cats during warmup to
> >> > help
> >> > light off the cats quicker, then diverted to the manifolds to help burn
> >> > off unburned HCs before the exhaust reaches the cats.
> >>
> >> Ok, so, he said its a straight 6 right? So its got 1 manifold right? Its
> >> got
> >> an O2 sensor in that manifold (or just below it). How can you pump air
> >> into
> >> the manifold (when its warmed up) and not give the O2 false info?

> >
> > By programming the PCM to ignore O2 sensor signals under
> > conditions when air is being injected upstream.
> >
> > Notice that in Jim and Tom's replies the absence of the word
> > 'always.'

>
> So its downstream when cold then diverted to atmosphere when it reaches
> norm operating temp, exept under certain conditions? What are those
> conditions?


Your question was;
"How can you pump air into
the manifold (when its warmed up) and not give the O2 false
info?"

I gave you the answer.
The rest has already been covered.
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Old 12-25-2005, 17:01   #10 (permalink)
Shoe Salesman
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Posts: n/a
Re: 92 f150 exhaust question


"aarcuda69062" <nonelson@sbcglobal.net> wrote in message
news:nonelson-35E9A0.16501325122005@newsclstr02.news.prodigy.com...
> In article <H_Crf.6351$pE4.3438@tornado.socal.rr.com>,
> "Shoe Salesman" <someone@microsoft.com> wrote:
>
>> "aarcuda69062" <nonelson@sbcglobal.net> wrote in message
>> news:nonelson-5C139A.13525925122005@newsclstr02.news.prodigy.com...
>> > In article <9ICrf.7450$ka.1602@tornado.socal.rr.com>,
>> > "Shoe Salesman" <someone@microsoft.com> wrote:
>> >
>> >> "Tom Adkins" <newton5@remove.comcast.net> wrote in message
>> >> news:hPadnbM-rdbooDPenZ2dnUVZ_tqdnZ2d@comcast.com...
>> >> > Shoe Salesman wrote:
>> >> >
>> >> >
>> >> >> I think you got it backwards, can't pump air into the manifold
>> >> >> above
>> >> >> the
>> >> >> O2 in closed loop, it would read too much O2. It will go upstream
>> >> >> when
>> >> >> cold, then downstream when hot. Sounds like it could be a CA only
>> >> >> thing
>> >> >> too. I think I would have a muffler shop weld the pipe on it, or
>> >> >> better
>> >> >> yet, get the correct part.
>> >> >>
>> >> >
>> >> >
>> >> >
>> >> > Nope Shoe,
>> >> > Jim has it right. The air is diverted to the cats during warmup to
>> >> > help
>> >> > light off the cats quicker, then diverted to the manifolds to help
>> >> > burn
>> >> > off unburned HCs before the exhaust reaches the cats.
>> >>
>> >> Ok, so, he said its a straight 6 right? So its got 1 manifold right?
>> >> Its
>> >> got
>> >> an O2 sensor in that manifold (or just below it). How can you pump air
>> >> into
>> >> the manifold (when its warmed up) and not give the O2 false info?
>> >
>> > By programming the PCM to ignore O2 sensor signals under
>> > conditions when air is being injected upstream.
>> >
>> > Notice that in Jim and Tom's replies the absence of the word
>> > 'always.'

>>
>> So its downstream when cold then diverted to atmosphere when it reaches
>> norm operating temp, exept under certain conditions? What are those
>> conditions?

>
> Your question was;
> "How can you pump air into
> the manifold (when its warmed up) and not give the O2 false
> info?"
>
> I gave you the answer.
> The rest has already been covered.


No, I just asked what those conditions were. What was covered was when
warmed up, it goes to the manifold. Then you said not "always". What I want
to know is the "not always" part when its warm. When during closed loop does
the ECM not look at the O2 (when is it injecting air in the manifold in
closed loop) like you said? If you don't know just say so, I'm just trying
to learn about the system here....


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