49 psi is the fuel rail pressure. It bleeds off pretty quickly when you
depress the Shraeder valve near the injectors. If it's truly running too
rich, it's likely that the upstream 02 sensor is going bad, that is the
sensor that sets the air-fuel mixture. Have you checked all your plugs for
wear and unusual appearance?

Jerry
--
Jerry Bransford
PP-ASEL N6TAY
See the Geezer Jeep at
http://members.***.net/jerrypb/
"M. E. Bye" <fxdyna@hotmail.com> wrote in message
news:2h3fj0p2u0tig9g9d8dbeug8i4hsq0s0eo@4ax.com...
> On Wed, 01 Sep 2004 17:39:45 -0500, M. E. Bye <fxdyna@hotmail.com>
> wrote:
>
>>About a week ago, my '98 TJ (2.5L, 5-speed, 71K miles) began missing
>>at highway speed, bucking like a bronco. I chalked it up to a bad
>>tank of gas, so I dumped in a bottle of HEET and a bottle of fuel
>>injector cleaner. The problem continued, so I did the same thing with
>>my next fill-up at a different station. No improvement. Since then,
>>I've changed the plugs, installed new wires, distributor cap and
>>rotor, have cleaned the throttle body, and have disconnected all
>>electrical connections to the throttle body and fuel injectors and
>>have sprayed electrical contact cleaner on them. I still have an
>>intermittent miss at speed. Not as severe as before, but I still have
>>the problem. What's next?
>>
>>Thanks in advance for any assistance!
>>
>>Mark
>>'98 TJ
>>'98 XJ
>
> Jerry,
>
> My buddy hooked up his code reader and no codes displayed. He does
> have a couple of questions tho...
> What is fuel pressure supposed to be and what is the "bleed down"
> rate? He also noted (by looking at the tailpipe) that it appears I'm
> running a bit rich, but also wondered if that had something to do with
> all the chemicals (the HEET and injector cleaner) that I'd had in the
> last couple tanks of gas.
>
> Really appreciate any help.
>
> Mark
> '98 TJ
> '98 XJ
>

 

49 psi is the fuel rail pressure. It bleeds off pretty quickly when you
depress the Shraeder valve near the injectors. If it's truly running too
rich, it's likely that the upstream 02 sensor is going bad, that is the
sensor that sets the air-fuel mixture. Have you checked all your plugs for
wear and unusual appearance?

Jerry
--
Jerry Bransford
PP-ASEL N6TAY
See the Geezer Jeep at
http://members.***.net/jerrypb/
"M. E. Bye" <fxdyna@hotmail.com> wrote in message
news:2h3fj0p2u0tig9g9d8dbeug8i4hsq0s0eo@4ax.com...
> On Wed, 01 Sep 2004 17:39:45 -0500, M. E. Bye <fxdyna@hotmail.com>
> wrote:
>
>>About a week ago, my '98 TJ (2.5L, 5-speed, 71K miles) began missing
>>at highway speed, bucking like a bronco. I chalked it up to a bad
>>tank of gas, so I dumped in a bottle of HEET and a bottle of fuel
>>injector cleaner. The problem continued, so I did the same thing with
>>my next fill-up at a different station. No improvement. Since then,
>>I've changed the plugs, installed new wires, distributor cap and
>>rotor, have cleaned the throttle body, and have disconnected all
>>electrical connections to the throttle body and fuel injectors and
>>have sprayed electrical contact cleaner on them. I still have an
>>intermittent miss at speed. Not as severe as before, but I still have
>>the problem. What's next?
>>
>>Thanks in advance for any assistance!
>>
>>Mark
>>'98 TJ
>>'98 XJ
>
> Jerry,
>
> My buddy hooked up his code reader and no codes displayed. He does
> have a couple of questions tho...
> What is fuel pressure supposed to be and what is the "bleed down"
> rate? He also noted (by looking at the tailpipe) that it appears I'm
> running a bit rich, but also wondered if that had something to do with
> all the chemicals (the HEET and injector cleaner) that I'd had in the
> last couple tanks of gas.
>
> Really appreciate any help.
>
> Mark
> '98 TJ
> '98 XJ
>

 

49 psi is the fuel rail pressure. It bleeds off pretty quickly when you
depress the Shraeder valve near the injectors. If it's truly running too
rich, it's likely that the upstream 02 sensor is going bad, that is the
sensor that sets the air-fuel mixture. Have you checked all your plugs for
wear and unusual appearance?

Jerry
--
Jerry Bransford
PP-ASEL N6TAY
See the Geezer Jeep at
http://members.***.net/jerrypb/
"M. E. Bye" <fxdyna@hotmail.com> wrote in message
news:2h3fj0p2u0tig9g9d8dbeug8i4hsq0s0eo@4ax.com...
> On Wed, 01 Sep 2004 17:39:45 -0500, M. E. Bye <fxdyna@hotmail.com>
> wrote:
>
>>About a week ago, my '98 TJ (2.5L, 5-speed, 71K miles) began missing
>>at highway speed, bucking like a bronco. I chalked it up to a bad
>>tank of gas, so I dumped in a bottle of HEET and a bottle of fuel
>>injector cleaner. The problem continued, so I did the same thing with
>>my next fill-up at a different station. No improvement. Since then,
>>I've changed the plugs, installed new wires, distributor cap and
>>rotor, have cleaned the throttle body, and have disconnected all
>>electrical connections to the throttle body and fuel injectors and
>>have sprayed electrical contact cleaner on them. I still have an
>>intermittent miss at speed. Not as severe as before, but I still have
>>the problem. What's next?
>>
>>Thanks in advance for any assistance!
>>
>>Mark
>>'98 TJ
>>'98 XJ
>
> Jerry,
>
> My buddy hooked up his code reader and no codes displayed. He does
> have a couple of questions tho...
> What is fuel pressure supposed to be and what is the "bleed down"
> rate? He also noted (by looking at the tailpipe) that it appears I'm
> running a bit rich, but also wondered if that had something to do with
> all the chemicals (the HEET and injector cleaner) that I'd had in the
> last couple tanks of gas.
>
> Really appreciate any help.
>
> Mark
> '98 TJ
> '98 XJ
>

 

On Thu, 2 Sep 2004 17:11:08 -0700, "Jerry Bransford" <jerrypb@***.net>
wrote:

>49 psi is the fuel rail pressure. It bleeds off pretty quickly when you
>depress the Shraeder valve near the injectors. If it's truly running too
>rich, it's likely that the upstream 02 sensor is going bad, that is the
>sensor that sets the air-fuel mixture. Have you checked all your plugs for
>wear and unusual appearance?
>
>Jerry

Yup. Changed the plugs the other day as part of my own effort to find
a diagnosis and cure. The old ones looked good. Brown-greyish
deposit on them. I changed 'em anyway, just to make sure.

 

On Thu, 2 Sep 2004 17:11:08 -0700, "Jerry Bransford" <jerrypb@***.net>
wrote:

>49 psi is the fuel rail pressure. It bleeds off pretty quickly when you
>depress the Shraeder valve near the injectors. If it's truly running too
>rich, it's likely that the upstream 02 sensor is going bad, that is the
>sensor that sets the air-fuel mixture. Have you checked all your plugs for
>wear and unusual appearance?
>
>Jerry

Yup. Changed the plugs the other day as part of my own effort to find
a diagnosis and cure. The old ones looked good. Brown-greyish
deposit on them. I changed 'em anyway, just to make sure.

 

On Thu, 2 Sep 2004 17:11:08 -0700, "Jerry Bransford" <jerrypb@***.net>
wrote:

>49 psi is the fuel rail pressure. It bleeds off pretty quickly when you
>depress the Shraeder valve near the injectors. If it's truly running too
>rich, it's likely that the upstream 02 sensor is going bad, that is the
>sensor that sets the air-fuel mixture. Have you checked all your plugs for
>wear and unusual appearance?
>
>Jerry

Yup. Changed the plugs the other day as part of my own effort to find
a diagnosis and cure. The old ones looked good. Brown-greyish
deposit on them. I changed 'em anyway, just to make sure.

 

i will, thanks

"L.W. (ßill) ------ III" <----------@***.net> wrote in message
news:4137AB20.88E819C@***.net...
> Put yourself back on a regular maintenance schedule:
> http://www.----------.com/lubeschedule.pdf
> God Bless America, ßill O|||||||O
> mailto:--------------------
>
> "Peter D." wrote:
> >
> > You might be very right.
> > I replaced the plugs too, and all ignition components (on different
> > ocassion)
> > The plugs looked like they were never replaced (gap was more than
double!)
> > *am not 1st owner :(*
> > but it does run great! :)

 

i will, thanks

"L.W. (ßill) ------ III" <----------@***.net> wrote in message
news:4137AB20.88E819C@***.net...
> Put yourself back on a regular maintenance schedule:
> http://www.----------.com/lubeschedule.pdf
> God Bless America, ßill O|||||||O
> mailto:--------------------
>
> "Peter D." wrote:
> >
> > You might be very right.
> > I replaced the plugs too, and all ignition components (on different
> > ocassion)
> > The plugs looked like they were never replaced (gap was more than
double!)
> > *am not 1st owner :(*
> > but it does run great! :)

 

i will, thanks

"L.W. (ßill) ------ III" <----------@***.net> wrote in message
news:4137AB20.88E819C@***.net...
> Put yourself back on a regular maintenance schedule:
> http://www.----------.com/lubeschedule.pdf
> God Bless America, ßill O|||||||O
> mailto:--------------------
>
> "Peter D." wrote:
> >
> > You might be very right.
> > I replaced the plugs too, and all ignition components (on different
> > ocassion)
> > The plugs looked like they were never replaced (gap was more than
double!)
> > *am not 1st owner :(*
> > but it does run great! :)

 

On Wed, 01 Sep 2004 17:39:45 -0500, M. E. Bye <fxdyna@hotmail.com>
wrote:

>About a week ago, my '98 TJ (2.5L, 5-speed, 71K miles) began missing
>at highway speed, bucking like a bronco. I chalked it up to a bad
>tank of gas, so I dumped in a bottle of HEET and a bottle of fuel
>injector cleaner. The problem continued, so I did the same thing with
>my next fill-up at a different station. No improvement. Since then,
>I've changed the plugs, installed new wires, distributor cap and
>rotor, have cleaned the throttle body, and have disconnected all
>electrical connections to the throttle body and fuel injectors and
>have sprayed electrical contact cleaner on them. I still have an
>intermittent miss at speed. Not as severe as before, but I still have
>the problem. What's next?
>
>Thanks in advance for any assistance!
>
>Mark
>'98 TJ
>'98 XJ

Well, by cracky, it's fixed. It didn't come about without a story,
though. I took off from work at noon yesterday (Friday) and set out
to my local AutoZone store to drop about $150 on new oxygen sensors.
En route, something happened that hadn't before. Specifically my
"CHECK ENGINE" light came on. Now I KNEW that I had to have some sort
of codes that would display (none did the previous day when my buddy
plugged in his code reader). So, when I got to AutoZone, I asked the
counter guy if he had a code reader, which he did. He checked it and
got a code "TPS/Pedal Travel Sensor". Well, neither one of us knew
what a Pedal Travel Sensor was, but both knew what a TPS was.
However, the counter guy still suggests strongly that I've got a fuel
filter problem and that should be my priority fix. I thanked him and
decided that it was now time to go see the Jeep repair guy at a
dealership. Drove crosstown and talked with the Jeep technician who
really felt it was the throttle position sensor, so I went to their
parts counter and asked if they had one. Nope, but they could order
it. I had 'em check with a dealership 35 miles down the road. They
had 3 of 'em. I got on the cellphone and asked them to hold one, I'd
be right there. An hour later, I've got the new one on and everything
is back to normal! Now I can get back to spending $$$ on my Jeep for
fun things.

Thanks to everyone who provided assistance with this.

Mark
'98 TJ
'98 XJ