'91 L98 6-Speed Running Rich

I have a '91 L98 w/ 84k that I recently changed the ignition module,
cap, rotor, wires, plugs, with no engine codes and the thing is still
running very rich.. can smell it. It has also recently stalled a few
times on me and I cannot start it until I let it sit for a few minutes,
almost like it's flooded. The idle also fluctuates frequently between
800-1000 rpms at idle. Someone had suggested a new EGR valve. Any
suggestions would be appreciated. Thanks.

Eric

"Koolman365" > wrote in message
ups.com...
>I have a '91 L98 w/ 84k that I recently changed the ignition module,
> cap, rotor, wires, plugs, with no engine codes and the thing is still
> running very rich.. can smell it. It has also recently stalled a few
> times on me and I cannot start it until I let it sit for a few minutes,
> almost like it's flooded. The idle also fluctuates frequently between
> 800-1000 rpms at idle. Someone had suggested a new EGR valve. Any
> suggestions would be appreciated. Thanks.
>
> Eric
>
You may have a sensor telling the computer that the engine is running cold
and it is in effect choking it (adding more fuel). If that is so it will
eventually shut you down by flooding it out. How's your fuel mileage? My
guess it that it sucks, (in a bad way ;-)).

Dad wrote:
> "Koolman365" > wrote in message
> ups.com...
>
>>I have a '91 L98 w/ 84k that I recently changed the ignition module,
>>cap, rotor, wires, plugs, with no engine codes and the thing is still
>>running very rich.. can smell it. It has also recently stalled a few
>>times on me and I cannot start it until I let it sit for a few minutes,
>>almost like it's flooded. The idle also fluctuates frequently between
>>800-1000 rpms at idle. Someone had suggested a new EGR valve. Any
>>suggestions would be appreciated. Thanks.
>>
>>Eric
>>
>
> You may have a sensor telling the computer that the engine is running cold
> and it is in effect choking it (adding more fuel). If that is so it will
> eventually shut you down by flooding it out. How's your fuel mileage? My
> guess it that it sucks, (in a bad way ;-)).
>
>
Good to see you back, Dad.
It was too 'f'ing quiet in here without you...

TomC
'90ZR1

Dad wrote:
> "Koolman365" > wrote in message
> ups.com...
> >I have a '91 L98 w/ 84k that I recently changed the ignition module,
> > cap, rotor, wires, plugs, with no engine codes and the thing is still
> > running very rich.. can smell it. It has also recently stalled a few
> > times on me and I cannot start it until I let it sit for a few minutes,
> > almost like it's flooded. The idle also fluctuates frequently between
> > 800-1000 rpms at idle. Someone had suggested a new EGR valve. Any
> > suggestions would be appreciated. Thanks.
> >
> > Eric
> >
> You may have a sensor telling the computer that the engine is running cold
> and it is in effect choking it (adding more fuel). If that is so it will
> eventually shut you down by flooding it out. How's your fuel mileage? My
> guess it that it sucks, (in a bad way ;-)).

Fuel mileage is not as good for sure, but nothing horrible. If a
sensor was bad, wouldn't the computer put out a code... there's nothing
in the computer that says anything is wrong. Any other suggestions? I
do get some popping in the exhaust occasionally when down-shifting as
well.

Eric

"Koolman365" > wrote in message
oups.com...
>
>
> Dad wrote:
>> "Koolman365" > wrote in message
>> ups.com...
>> >I have a '91 L98 w/ 84k that I recently changed the ignition module,
>> > cap, rotor, wires, plugs, with no engine codes and the thing is still
>> > running very rich.. can smell it. It has also recently stalled a few
>> > times on me and I cannot start it until I let it sit for a few minutes,
>> > almost like it's flooded. The idle also fluctuates frequently between
>> > 800-1000 rpms at idle. Someone had suggested a new EGR valve. Any
>> > suggestions would be appreciated. Thanks.
>> >
>> > Eric
>> >
>> You may have a sensor telling the computer that the engine is running
>> cold
>> and it is in effect choking it (adding more fuel). If that is so it will
>> eventually shut you down by flooding it out. How's your fuel mileage? My
>> guess it that it sucks, (in a bad way ;-)).
>
> Fuel mileage is not as good for sure, but nothing horrible. If a
> sensor was bad, wouldn't the computer put out a code... there's nothing
> in the computer that says anything is wrong. Any other suggestions? I
> do get some popping in the exhaust occasionally when down-shifting as
> well.
>
> Eric
>
No more suggestions, but I just went through this same scenario with my sons
91 and we changed all of the stuff you did and more before we thought it was
fixed. Ran good when I left and while it was a cold engine. Right after we
"fixed it" it left him setting in the bank drive up window on Friday
afternoon. Had it scanned and it showed a faulty temperature sensor. Changed
it and it now runs like a charm. Is that your problem, don't know, discount
it if you want it never threw a code.

Dad is right , check the water temperature sensore first. And check your
fuel pressure regulator. A ruptured diaphragm could cause the problem. RPM
fluctuation could indicate an intake leak.


"Dad" > wrote in message
...
>
> "Koolman365" > wrote in message
> oups.com...
> >
> >
> > Dad wrote:
> >> "Koolman365" > wrote in message
> >> ups.com...
> >> >I have a '91 L98 w/ 84k that I recently changed the ignition module,
> >> > cap, rotor, wires, plugs, with no engine codes and the thing is still
> >> > running very rich.. can smell it. It has also recently stalled a few
> >> > times on me and I cannot start it until I let it sit for a few
minutes,
> >> > almost like it's flooded. The idle also fluctuates frequently
between
> >> > 800-1000 rpms at idle. Someone had suggested a new EGR valve. Any
> >> > suggestions would be appreciated. Thanks.
> >> >
> >> > Eric
> >> >
> >> You may have a sensor telling the computer that the engine is running
> >> cold
> >> and it is in effect choking it (adding more fuel). If that is so it
will
> >> eventually shut you down by flooding it out. How's your fuel mileage?
My
> >> guess it that it sucks, (in a bad way ;-)).
> >
> > Fuel mileage is not as good for sure, but nothing horrible. If a
> > sensor was bad, wouldn't the computer put out a code... there's nothing
> > in the computer that says anything is wrong. Any other suggestions? I
> > do get some popping in the exhaust occasionally when down-shifting as
> > well.
> >
> > Eric
> >
> No more suggestions, but I just went through this same scenario with my
sons
> 91 and we changed all of the stuff you did and more before we thought it
was
> fixed. Ran good when I left and while it was a cold engine. Right after we
> "fixed it" it left him setting in the bank drive up window on Friday
> afternoon. Had it scanned and it showed a faulty temperature sensor.
Changed
> it and it now runs like a charm. Is that your problem, don't know,
discount
> it if you want it never threw a code.
>
>

To Dad and tom_I_35806,
What would the water temperature sensor have to do with anything? Mine
works fine as far as I know it, temperature seems accurate. As far as
the intake, you're referring to the intake manifold I suppose. How
would I diagnose that? The idle fluctuation gets worse if I throw the
AC on... don't think the AC has anything to do with it, just think that
the AC exaggerates whatever problem it is. Thanks again.

Eric

the weather pack connection is the one for the SENSOR that reports
back to the ECM (electronic control module), the single wire
connector is the one for the temperature gauge SENDER.
as far as the fuel pressure regulator, just pull the vacuum line off
of it and engage the fuel pump by turning the ignition switch to the
run position. it should give the fuel pump a 3 second burst. if it is
bad it will pump fuel out of the regulator.
there are a lot of things that can make it run rich that MAY not set a
code or turn the SES (service engine soon) light on. O2 sensor, CTS
(coolant temperature sensor) MAF (mass airflow sensor) bad injectors,
rupture in the fuel pressure regulator.
find some one who has a scan tool (and understands what they are
looking at) and look at the data stream for the swing on the O2 and
CTS voltage, look at the data stream for the MAF.
more than likely Dad and Tom are right on the money on this one.
look for any stored DTC (diagnostic trouble codes) while you are in
there.

PS, glad to see you did not stay away to long Dad, i have always
enjoyed your posts and your vast depth of knowledge.
now where the hell is Diode??????
Greg Nettles
On 7 Jul 2005 08:42:08 -0700, "Koolman365" >
wrote:

>To Dad and tom_I_35806,
>What would the water temperature sensor have to do with anything? Mine
>works fine as far as I know it, temperature seems accurate. As far as
>the intake, you're referring to the intake manifold I suppose. How
>would I diagnose that? The idle fluctuation gets worse if I throw the
>AC on... don't think the AC has anything to do with it, just think that
>the AC exaggerates whatever problem it is. Thanks again.
>
>Eric

Sensor can give a erroneous bit of information to the computer and therefore
sends an incorrect request for more fuel. The sending unit for your coolant
temperature gage may not be the same as the one used to control your fuel.
Do you have more than one temperature sensor and did you have a scan tool
check it? It don't have to set a code that would appear in your DIC to be a
faulty sensor. Sorry, I can't look it up, I no longer have a manual for my
'92 which may be different anyway with the LT1 and its reverse flow coolant.

Dad
--
Life is a sexually transmitted condition that is always fatal.


"Koolman365" > wrote in message
oups.com...
> To Dad and tom_I_35806,
> What would the water temperature sensor have to do with anything? Mine
> works fine as far as I know it, temperature seems accurate. As far as
> the intake, you're referring to the intake manifold I suppose. How
> would I diagnose that? The idle fluctuation gets worse if I throw the
> AC on... don't think the AC has anything to do with it, just think that
> the AC exaggerates whatever problem it is. Thanks again.
>
> Eric
>

"Dad" > wrote in message
...
> Sensor can give a erroneous bit of information to the computer and
> therefore sends an incorrect request for more fuel. The sending unit for
> your coolant temperature gage may not be the same as the one used to
> control your fuel. Do you have more than one temperature sensor and did
> you have a scan tool check it? It don't have to set a code that would
> appear in your DIC to be a faulty sensor. Sorry, I can't look it up, I no
> longer have a manual for my '92 which may be different anyway with the LT1
> and its reverse flow coolant.
>
> Dad
> --

A bad O2 sensor can also make the engine rich.

Al