1992 Corvette Runs Rough and Loss of Power over 3000 RPM

All,

I have a 1992 Corvette Vin P 350 automatic and it has me stumped.
Nothing has changed on the way it runs and I have replaced the
following. New Opti Spark (TWICE) new GM Unit. New Coil, New Module,
New Fuel Pump, New Injectors, New Plugs (Double Platinum) Factory, New
plug wires, removed and cleaned EGR works perfect, Checked compression
all at 190/200 PSI. Bought Snap-On Scan Tool and checked system. Oh,
there were no codes and the check engine light was not on. With Snap-
On Scanner I get a (28 QDM fault) Fan relay circuit. Strange since
the Fan(s) both work perfectly as does the airconditioner. Other than
that nothing shows to be throwing a code. Ohm checked the coil and
nothing out of range. Replaced knock sensors. This does not have an
ESC box since it is a 1992. The ECM does ECS function. With the Snap-
On code reader all readings are within normal and it says it is OK to
drive. The timing, sensors, and such all read within normal range per
the Factory Service Manual Indications Page. The timing moves advance
and retard when the throttle is depressed. I am at a loss and want to
correct the problem. The nice people at Vista Chevrolet refused to
work on the car. I assume since it is a 1992 and ALDL they did not
want to take the time to diagnose the problem since it is not OBDII
where all you have to do is plug in and get a code. Oh, in park when
it reved it does rev up but slowly and in gear it stumbles over 3000
RPM. It idles like it has a miss but was doing the same thing before
I started.

fuel pressure? original filter? fuel pump?

--
RS
2006 FLSTNI
2002 1200C
1991 FLSTF
"What shall we use to fill the empty spaces where we use to talk?"
"Von" > wrote in message
oups.com...
> All,
>
> I have a 1992 Corvette Vin P 350 automatic and it has me stumped.
> Nothing has changed on the way it runs and I have replaced the
> following. New Opti Spark (TWICE) new GM Unit. New Coil, New Module,
> New Fuel Pump, New Injectors, New Plugs (Double Platinum) Factory, New
> plug wires, removed and cleaned EGR works perfect, Checked compression
> all at 190/200 PSI. Bought Snap-On Scan Tool and checked system. Oh,
> there were no codes and the check engine light was not on. With Snap-
> On Scanner I get a (28 QDM fault) Fan relay circuit. Strange since
> the Fan(s) both work perfectly as does the airconditioner. Other than
> that nothing shows to be throwing a code. Ohm checked the coil and
> nothing out of range. Replaced knock sensors. This does not have an
> ESC box since it is a 1992. The ECM does ECS function. With the Snap-
> On code reader all readings are within normal and it says it is OK to
> drive. The timing, sensors, and such all read within normal range per
> the Factory Service Manual Indications Page. The timing moves advance
> and retard when the throttle is depressed. I am at a loss and want to
> correct the problem. The nice people at Vista Chevrolet refused to
> work on the car. I assume since it is a 1992 and ALDL they did not
> want to take the time to diagnose the problem since it is not OBDII
> where all you have to do is plug in and get a code. Oh, in park when
> it reved it does rev up but slowly and in gear it stumbles over 3000
> RPM. It idles like it has a miss but was doing the same thing before
> I started.
>

"Von" > wrote in message
oups.com...
---snip the parts I don't have an answer to---
> The nice people at Vista Chevrolet refused to
> work on the car. I assume since it is a 1992 and ALDL
> they did not
> want to take the time to diagnose the problem since it is
> not OBDII
> where all you have to do is plug in and get a code.

had a GM dealer try and tell me they didn't work on an 84
vette any longer.
a quick call to GM and then a return call from that same
dealer
wanting to make an appointment to work on my car.
hmmm?
naturally, I took it to a different GM dealer and
told them that GM said dealers would still work on my 84.

my2¢
--
"Key"
=====

"RS" > wrote in message
news:I9TRh.124$jG5.61@trndny09...
> fuel pressure?

I had to put a fuel regulater on my 84.
oh? forgot, its not stock...

> original filter?

could be ?

> fuel pump?

he already got a new fuel pump.

--
"Key"
>
> --
> RS
> 2006 FLSTNI
> 2002 1200C
> 1991 FLSTF
> "What shall we use to fill the empty spaces where we use
> to talk?"
> "Von" > wrote in message
> oups.com...
>> All,
>>
>> I have a 1992 Corvette Vin P 350 automatic and it has me
>> stumped.
>> Nothing has changed on the way it runs and I have
>> replaced the
>> following. New Opti Spark (TWICE) new GM Unit. New
>> Coil, New Module,
>> New Fuel Pump, New Injectors, New Plugs (Double Platinum)
>> Factory, New
>> plug wires, removed and cleaned EGR works perfect,
>> Checked compression
>> all at 190/200 PSI. Bought Snap-On Scan Tool and checked
>> system. Oh,
>> there were no codes and the check engine light was not
>> on. With Snap-
>> On Scanner I get a (28 QDM fault) Fan relay circuit.
>> Strange since
>> the Fan(s) both work perfectly as does the
>> airconditioner. Other than
>> that nothing shows to be throwing a code. Ohm checked
>> the coil and
>> nothing out of range. Replaced knock sensors. This does
>> not have an
>> ESC box since it is a 1992. The ECM does ECS function.
>> With the Snap-
>> On code reader all readings are within normal and it says
>> it is OK to
>> drive. The timing, sensors, and such all read within
>> normal range per
>> the Factory Service Manual Indications Page. The timing
>> moves advance
>> and retard when the throttle is depressed. I am at a
>> loss and want to
>> correct the problem. The nice people at Vista Chevrolet
>> refused to
>> work on the car. I assume since it is a 1992 and ALDL
>> they did not
>> want to take the time to diagnose the problem since it is
>> not OBDII
>> where all you have to do is plug in and get a code. Oh,
>> in park when
>> it reved it does rev up but slowly and in gear it
>> stumbles over 3000
>> RPM. It idles like it has a miss but was doing the same
>> thing before
>> I started.
>>
>
>

Plugged cats perhaps?

Von wrote:
> All,
>
> I have a 1992 Corvette Vin P 350 automatic and it has me stumped.
> Nothing has changed on the way it runs and I have replaced the
> following. New Opti Spark (TWICE) new GM Unit. New Coil, New Module,
> New Fuel Pump, New Injectors, New Plugs (Double Platinum) Factory, New
> plug wires, removed and cleaned EGR works perfect, Checked compression
> all at 190/200 PSI. Bought Snap-On Scan Tool and checked system. Oh,
> there were no codes and the check engine light was not on. With Snap-
> On Scanner I get a (28 QDM fault) Fan relay circuit. Strange since
> the Fan(s) both work perfectly as does the airconditioner. Other than
> that nothing shows to be throwing a code. Ohm checked the coil and
> nothing out of range. Replaced knock sensors. This does not have an
> ESC box since it is a 1992. The ECM does ECS function. With the Snap-
> On code reader all readings are within normal and it says it is OK to
> drive. The timing, sensors, and such all read within normal range per
> the Factory Service Manual Indications Page. The timing moves advance
> and retard when the throttle is depressed. I am at a loss and want to
> correct the problem. The nice people at Vista Chevrolet refused to
> work on the car. I assume since it is a 1992 and ALDL they did not
> want to take the time to diagnose the problem since it is not OBDII
> where all you have to do is plug in and get a code. Oh, in park when
> it reved it does rev up but slowly and in gear it stumbles over 3000
> RPM. It idles like it has a miss but was doing the same thing before
> I started.
>

"Bob I" > wrote in message
...
> Plugged cats perhaps?

never have liked "cats"...
:-)
--
"Key"
=====

> Von wrote:
>> All,
>>
>> I have a 1992 Corvette Vin P 350 automatic and it has me
>> stumped.
>> Nothing has changed on the way it runs and I have
>> replaced the
>> following. New Opti Spark (TWICE) new GM Unit. New
>> Coil, New Module,
>> New Fuel Pump, New Injectors, New Plugs (Double Platinum)
>> Factory, New
>> plug wires, removed and cleaned EGR works perfect,
>> Checked compression
>> all at 190/200 PSI. Bought Snap-On Scan Tool and checked
>> system. Oh,
>> there were no codes and the check engine light was not
>> on. With Snap-
>> On Scanner I get a (28 QDM fault) Fan relay circuit.
>> Strange since
>> the Fan(s) both work perfectly as does the
>> airconditioner. Other than
>> that nothing shows to be throwing a code. Ohm checked
>> the coil and
>> nothing out of range. Replaced knock sensors. This does
>> not have an
>> ESC box since it is a 1992. The ECM does ECS function.
>> With the Snap-
>> On code reader all readings are within normal and it says
>> it is OK to
>> drive. The timing, sensors, and such all read within
>> normal range per
>> the Factory Service Manual Indications Page. The timing
>> moves advance
>> and retard when the throttle is depressed. I am at a
>> loss and want to
>> correct the problem. The nice people at Vista Chevrolet
>> refused to
>> work on the car. I assume since it is a 1992 and ALDL
>> they did not
>> want to take the time to diagnose the problem since it is
>> not OBDII
>> where all you have to do is plug in and get a code. Oh,
>> in park when
>> it reved it does rev up but slowly and in gear it
>> stumbles over 3000
>> RPM. It idles like it has a miss but was doing the same
>> thing before
>> I started.
>>

Speaking of Cats, I just had a Flowmaster installed on my truck, dealer even
asked if i wanted wild or mild. I went with wild. I swear i cant even hear a
difference! due to the 2 or 3 converters ahead of it.. FLUSH $$$

--
RS
2006 FLSTNI
2002 1200C
1991 FLSTF
"What shall we use to fill the empty spaces where we use to talk?"
"'Key" > wrote in message
. ..
> "Bob I" > wrote in message
> ...
>> Plugged cats perhaps?
>
> never have liked "cats"...
> :-)
> --
> "Key"
> =====
>
>>

Try watching the:

O2 Sensor readings when you bring it up to 3K RPM, and see if it goes lean
or rich.

Block Learn and integrator are also an important diagnostic reading. 128 and
128 is optimum, but Chip updates can make these readings worthless.

Get back to me with the O2 readings as you raise the RPM slowly and the miss
just starts.

RK

"'Key" > wrote in message
. ..
> "Bob I" > wrote in message
> ...
>> Plugged cats perhaps?
>
> never have liked "cats"...
> :-)
> --
> "Key"
> =====
>
>> Von wrote:
>>> All,
>>>
>>> I have a 1992 Corvette Vin P 350 automatic and it has me stumped.
>>> Nothing has changed on the way it runs and I have replaced the
>>> following. New Opti Spark (TWICE) new GM Unit. New Coil, New Module,
>>> New Fuel Pump, New Injectors, New Plugs (Double Platinum) Factory, New
>>> plug wires, removed and cleaned EGR works perfect, Checked compression
>>> all at 190/200 PSI. Bought Snap-On Scan Tool and checked system. Oh,
>>> there were no codes and the check engine light was not on. With Snap-
>>> On Scanner I get a (28 QDM fault) Fan relay circuit. Strange since
>>> the Fan(s) both work perfectly as does the airconditioner. Other than
>>> that nothing shows to be throwing a code. Ohm checked the coil and
>>> nothing out of range. Replaced knock sensors. This does not have an
>>> ESC box since it is a 1992. The ECM does ECS function. With the Snap-
>>> On code reader all readings are within normal and it says it is OK to
>>> drive. The timing, sensors, and such all read within normal range per
>>> the Factory Service Manual Indications Page. The timing moves advance
>>> and retard when the throttle is depressed. I am at a loss and want to
>>> correct the problem. The nice people at Vista Chevrolet refused to
>>> work on the car. I assume since it is a 1992 and ALDL they did not
>>> want to take the time to diagnose the problem since it is not OBDII
>>> where all you have to do is plug in and get a code. Oh, in park when
>>> it reved it does rev up but slowly and in gear it stumbles over 3000
>>> RPM. It idles like it has a miss but was doing the same thing before
>>> I started.
>>>
>
>

Changed the fuel pump and filter and checked the pressure and it was
within norms with and without vacuum.

Checked the converters and they are free and open.

The O2 readings were right on target.

128 is right on where it shows on the Snap-On scan tool.

No aftermarket chip and it is seated correctly. No FETs look to be
defective on any of the QDM ports.

Vista Chevrolet sucks (delete expletive)... I thougth I would take it
to Bill Heard Chevrolet next.

The 28 QDM fault is something that I have a call into Gordon Killebrew
in Kentucky. He has been ill and out of pocket. He is the guy that
worked the Corvette Action Center during the C4 build and now has his
own company and does phone consulting.

I am at a loss here as all the usual suspects have been changed and or
inspected.

"RS" > wrote in message
news:_UWRh.3233$Rg2.2113@trndny02...
> Speaking of Cats, I just had a Flowmaster installed on my
> truck, dealer even asked if i wanted wild or mild. I went
> with wild. I swear i cant even hear a difference! due to
> the 2 or 3 converters ahead of it.. FLUSH $$$
>
> --
> RS
> 2006 FLSTNI
> 2002 1200C
> 1991 FLSTF
> "What shall we use to fill the empty spaces where we use
> to talk?"

I got flowmasters on my 84.
converters ????
:-)
--
"Key"
=====