Help please...

98 Mustang GT..

Crappy gas mileage (15~16mpg around city with a tiny bit of highway). I used
to get a lot more.. 20+. This is EASY driving no less.

I was welding in hangers for the mufflers (managed to snag some OEM hangers)
and I'll be damned.. I saw greyish-white smoke leaking from 2 cats.. the
same 'one' on each side (driver & passenger). It seems I have 6 of them
total.. they are the ones right before the last O2 sensor I think. I'll get
a better look when it warms up. I immediately thought coolant, but the
coolant level hasn't dropped a bit! Oil level is good too! Also, the car has
been running better & better on its own... the stutter is *almost*
completely gone & I haven't touched anything.. 'cept exhaust. Any ideas?
Thanks. And HAPPY HOLIDAYS!!!

-Mike

--
A happy kid behind the wheel of a 98 Mustang GT
Cold air intake
FRPP 3.73 gears
Steeda Tri-Ax Shifter
Flowmaster 40 Series mufflers (self-installed woohoo)
Hi-speed fan switch
255/60R-15 rear tires
Subframe connectors

Mike, I don't know whether its applicable to you, but here in Pa in November
they start putting a funky additive in the gas to reduce emissions in the
winter. Then in march they go back to the rgular mix. I have found that my
gas milage goes to **** with this mix.Preformance sucks too.Do they do this
out your way?

Dave
> wrote in message
m...
> 98 Mustang GT..
>
> Crappy gas mileage (15~16mpg around city with a tiny bit of highway). I
> used
> to get a lot more.. 20+. This is EASY driving no less.
>
> I was welding in hangers for the mufflers (managed to snag some OEM
> hangers)
> and I'll be damned.. I saw greyish-white smoke leaking from 2 cats.. the
> same 'one' on each side (driver & passenger). It seems I have 6 of them
> total.. they are the ones right before the last O2 sensor I think. I'll
> get
> a better look when it warms up. I immediately thought coolant, but the
> coolant level hasn't dropped a bit! Oil level is good too! Also, the car
> has
> been running better & better on its own... the stutter is *almost*
> completely gone & I haven't touched anything.. 'cept exhaust. Any ideas?
> Thanks. And HAPPY HOLIDAYS!!!
>
> -Mike
>
> --
> A happy kid behind the wheel of a 98 Mustang GT
> Cold air intake
> FRPP 3.73 gears
> Steeda Tri-Ax Shifter
> Flowmaster 40 Series mufflers (self-installed woohoo)
> Hi-speed fan switch
> 255/60R-15 rear tires
> Subframe connectors
>
>
>
>

they call it"oxygenated" gas.

Dave

"Deputy Dog" > wrote in message
news:5p2yd.4069$vF5.4052@trndny07...
> Mike, I don't know whether its applicable to you, but here in Pa in
> November they start putting a funky additive in the gas to reduce
> emissions in the winter. Then in march they go back to the rgular mix. I
> have found that my gas milage goes to **** with this mix.Preformance sucks
> too.Do they do this out your way?
>
> Dave
> > wrote in message
> m...
>> 98 Mustang GT..
>>
>> Crappy gas mileage (15~16mpg around city with a tiny bit of highway). I
>> used
>> to get a lot more.. 20+. This is EASY driving no less.
>>
>> I was welding in hangers for the mufflers (managed to snag some OEM
>> hangers)
>> and I'll be damned.. I saw greyish-white smoke leaking from 2 cats.. the
>> same 'one' on each side (driver & passenger). It seems I have 6 of them
>> total.. they are the ones right before the last O2 sensor I think. I'll
>> get
>> a better look when it warms up. I immediately thought coolant, but the
>> coolant level hasn't dropped a bit! Oil level is good too! Also, the car
>> has
>> been running better & better on its own... the stutter is *almost*
>> completely gone & I haven't touched anything.. 'cept exhaust. Any ideas?
>> Thanks. And HAPPY HOLIDAYS!!!
>>
>> -Mike
>>
>> --
>> A happy kid behind the wheel of a 98 Mustang GT
>> Cold air intake
>> FRPP 3.73 gears
>> Steeda Tri-Ax Shifter
>> Flowmaster 40 Series mufflers (self-installed woohoo)
>> Hi-speed fan switch
>> 255/60R-15 rear tires
>> Subframe connectors
>>
>>
>>
>>
>
>

I haven't heard anything a/b it... :x

-Mike

--
A happy kid behind the wheel of a 98 Mustang GT
Cold air intake
FRPP 3.73 gears
Steeda Tri-Ax Shifter
Flowmaster 40 Series mufflers (self-installed woohoo)
Hi-speed fan switch
255/60R-15 rear tires
Subframe connectors


"Deputy Dog" > wrote in message
news:5p2yd.4069$vF5.4052@trndny07...
> Mike, I don't know whether its applicable to you, but here in Pa in
November
> they start putting a funky additive in the gas to reduce emissions in the
> winter. Then in march they go back to the rgular mix. I have found that
my
> gas milage goes to **** with this mix.Preformance sucks too.Do they do
this
> out your way?
>
> Dave
> > wrote in message
> m...
> > 98 Mustang GT..
> >
> > Crappy gas mileage (15~16mpg around city with a tiny bit of highway). I
> > used
> > to get a lot more.. 20+. This is EASY driving no less.
> >
> > I was welding in hangers for the mufflers (managed to snag some OEM
> > hangers)
> > and I'll be damned.. I saw greyish-white smoke leaking from 2 cats.. the
> > same 'one' on each side (driver & passenger). It seems I have 6 of them
> > total.. they are the ones right before the last O2 sensor I think. I'll
> > get
> > a better look when it warms up. I immediately thought coolant, but the
> > coolant level hasn't dropped a bit! Oil level is good too! Also, the car
> > has
> > been running better & better on its own... the stutter is *almost*
> > completely gone & I haven't touched anything.. 'cept exhaust. Any ideas?
> > Thanks. And HAPPY HOLIDAYS!!!
> >
> > -Mike
> >
> > --
> > A happy kid behind the wheel of a 98 Mustang GT
> > Cold air intake
> > FRPP 3.73 gears
> > Steeda Tri-Ax Shifter
> > Flowmaster 40 Series mufflers (self-installed woohoo)
> > Hi-speed fan switch
> > 255/60R-15 rear tires
> > Subframe connectors
> >
> >
> >
> >
>
>

wrote:

> 98 Mustang GT..
>
> Crappy gas mileage (15~16mpg around city with a tiny bit of highway). I
> used to get a lot more.. 20+. This is EASY driving no less.
>
> I was welding in hangers for the mufflers (managed to snag some OEM
> hangers) and I'll be damned.. I saw greyish-white smoke leaking from 2
> cats.. the same 'one' on each side (driver & passenger). It seems I have 6
> of them total.. they are the ones right before the last O2 sensor I think.
> I'll get a better look when it warms up. I immediately thought coolant,
> but the coolant level hasn't dropped a bit! Oil level is good too! Also,
> the car has been running better & better on its own... the stutter is
> *almost* completely gone & I haven't touched anything.. 'cept exhaust. Any
> ideas? Thanks. And HAPPY HOLIDAYS!!!
>
> -Mike
>
> --
> A happy kid behind the wheel of a 98 Mustang GT
> Cold air intake
> FRPP 3.73 gears
> Steeda Tri-Ax Shifter
> Flowmaster 40 Series mufflers (self-installed woohoo)
> Hi-speed fan switch
> 255/60R-15 rear tires
> Subframe connectors
How many miles on the engine? Is the O2 sensor the original one? These
sensors do wear out. A sign that they're going bad is your gas mileage
getting slowly worse. They default to a rich mixture when they start going
bad - this is so you don't burn your engine with a lean mixture.
Rich mixture means you burn more gasoline than normal - so your gas mileage
gets gradually worse.


hope this helps,

Oskar

I did have codes for the rear 2 O2 sensors, but they went away. 122k miles
on the car. Dont' know if the sensors are original.. they probably are.

-Mike

--
A happy kid behind the wheel of a 98 Mustang GT
Cold air intake
FRPP 3.73 gears
Steeda Tri-Ax Shifter
Flowmaster 40 Series mufflers (self-installed woohoo)
Hi-speed fan switch
255/60R-15 rear tires
Subframe connectors


"boo" > wrote in message
m...
> wrote:
>
> > 98 Mustang GT..
> >
> > Crappy gas mileage (15~16mpg around city with a tiny bit of highway). I
> > used to get a lot more.. 20+. This is EASY driving no less.
> >
> > I was welding in hangers for the mufflers (managed to snag some OEM
> > hangers) and I'll be damned.. I saw greyish-white smoke leaking from 2
> > cats.. the same 'one' on each side (driver & passenger). It seems I have
6
> > of them total.. they are the ones right before the last O2 sensor I
think.
> > I'll get a better look when it warms up. I immediately thought coolant,
> > but the coolant level hasn't dropped a bit! Oil level is good too! Also,
> > the car has been running better & better on its own... the stutter is
> > *almost* completely gone & I haven't touched anything.. 'cept exhaust.
Any
> > ideas? Thanks. And HAPPY HOLIDAYS!!!
> >
> > -Mike
> >
> > --
> > A happy kid behind the wheel of a 98 Mustang GT
> > Cold air intake
> > FRPP 3.73 gears
> > Steeda Tri-Ax Shifter
> > Flowmaster 40 Series mufflers (self-installed woohoo)
> > Hi-speed fan switch
> > 255/60R-15 rear tires
> > Subframe connectors
> How many miles on the engine? Is the O2 sensor the original one? These
> sensors do wear out. A sign that they're going bad is your gas mileage
> getting slowly worse. They default to a rich mixture when they start
going
> bad - this is so you don't burn your engine with a lean mixture.
> Rich mixture means you burn more gasoline than normal - so your gas
mileage
> gets gradually worse.
>
>
> hope this helps,
>
> Oskar
>
>

Interesting... I just (out of curiousity) romped on it while the car was
semi-cold.. almost warmed up. No stutter *at all* to 4,500RPM. I didn't
wanna go higher.. and even that was making me uncomfortable. I did it three
times.. not a single hint of a stutter.. then I drove it for another 15 mins
to let it warm up.. stomped on it.. stuttered a bit =(.

-Mike

--
A happy kid behind the wheel of a 98 Mustang GT
Cold air intake
FRPP 3.73 gears
Steeda Tri-Ax Shifter
Flowmaster 40 Series mufflers (self-installed woohoo)
Hi-speed fan switch
255/60R-15 rear tires
Subframe connectors


> wrote in message
m...
> 98 Mustang GT..
>
> Crappy gas mileage (15~16mpg around city with a tiny bit of highway). I
used
> to get a lot more.. 20+. This is EASY driving no less.
>
> I was welding in hangers for the mufflers (managed to snag some OEM
hangers)
> and I'll be damned.. I saw greyish-white smoke leaking from 2 cats.. the
> same 'one' on each side (driver & passenger). It seems I have 6 of them
> total.. they are the ones right before the last O2 sensor I think. I'll
get
> a better look when it warms up. I immediately thought coolant, but the
> coolant level hasn't dropped a bit! Oil level is good too! Also, the car
has
> been running better & better on its own... the stutter is *almost*
> completely gone & I haven't touched anything.. 'cept exhaust. Any ideas?
> Thanks. And HAPPY HOLIDAYS!!!
>
> -Mike
>
> --
> A happy kid behind the wheel of a 98 Mustang GT
> Cold air intake
> FRPP 3.73 gears
> Steeda Tri-Ax Shifter
> Flowmaster 40 Series mufflers (self-installed woohoo)
> Hi-speed fan switch
> 255/60R-15 rear tires
> Subframe connectors
>
>
>
>

It could also be that the fuel trims aren't quite right. Did you reset
the PCM after the exhaust install? You might try this just to clear all
the trims and let the PCM re-adapt.

It sounds like you've had an OBD scanner on there? True?

O2 sensors can cause this as well as the EGR system.
..
Dan
2003 Cobra convertible
With some stuff and things

I didn't reset the PCM via battery-disconnect yet.. I guess I could. What
are "fuel trims"? (Excuse the ignorance please). Yeah.. I've had an OBDII
scanner on it (I have a coder reader)... and come to think of it.. the
driver-side O2 sensor is about 40k miles old. The passenger side I think is
original. I replaced the EGR valve roughly 20k miles ago.. maybe less.

-Mike

--
A happy kid behind the wheel of a 98 Mustang GT
Cold air intake
FRPP 3.73 gears
Steeda Tri-Ax Shifter
Flowmaster 40 Series mufflers (self-installed woohoo)
Hi-speed fan switch
255/60R-15 rear tires
Subframe connectors


"Dan" > wrote in message
oups.com...
> It could also be that the fuel trims aren't quite right. Did you reset
> the PCM after the exhaust install? You might try this just to clear all
> the trims and let the PCM re-adapt.
>
> It sounds like you've had an OBD scanner on there? True?
>
> O2 sensors can cause this as well as the EGR system.
> .
> Dan
> 2003 Cobra convertible
> With some stuff and things
>

The PCM maintains a set of parameters that allow it to adapt the
changes in the system over time. Some of these are short term fuel
trims (STFT) and long term fuel trims (LTFT) which are time averaged
parameters that the PCM uses to shift the AFR. For example, if your car
tends to run lean, the fuel trims will cause the mixture to be a little
richer to accomodate this. The long term fuel trims are also used by
the PCM at WOT as the open loop fuel modifier (OLFM).

It can happen, for a number of reasons, that the trims shift too far
and cause some mild drivability issues. It's not very common but it can
happen.

..
Dan
2003 Cobra convertible
With some stuff and things