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Vehicle make/model = 2002 Pontiac Grand Am
Mileage = 97000
Engine size = 3.4L
dash lights = SES
codes = P0404; P0300
work done prior = None
work done to repair = Replaced fuel filter, fuel pressure regulator,
plugs, plug wires, air filter, and EGR valve. The EGR valve was replaced
after the service engine soon light came on. All other repairs were
made before the light came on but after symptoms started to appear.
tech = mw
question = The thing surges,sputters, and just flat runs bad. has no
power to pull itself up hills. If I drive it like there's an egg under
the gas pedal, I can run 80 mph on flat ground easily. Start up a grade
of any sort and it falls on it's face. Starting out from a dead stop is
an adventure too. That's where it does most of it's spitting and
sputtering. It has good exhaust flow and no rattling coming from the
catalytic converter. What am I missing here? Could a bad gas cap cause
this?
Could it be a bad PCM?
MW:
These conditions sure do sound like a plugged cat. converter. Placing your
hand over the tailpipe when revving engine when it has no power can be
misleading unless you have done it many times before, or can compare to a
car with the same engine. A backpressure test is the proper way to test
that. a plugged converter wil give lack of power on acceleration, misfire
codes, and egr position codes.
Aside from a plugged convertor, low fuel pressure can also cause this, but
not the EGR code. A plugged EGR passage to the intake will casue EGR
codes, but not misfire and no power.
Restricted injectors will missfires and no power, but not EGR codes.
Suggest having an exhaust backpressure test done.
VISITOR:
I forgot to mention that I was a tech for a bit over 12 years but drivability
wasn't one of my stronger suits. I have good exhaust flow. I unplugged the
EGR valve and test drove the car a short distance. The problem is still
there but not half as bad as it was. It is actually a lot better. Initial
acceleration is very acceptable now and will pull hills with very little problem.
Still thinking converter? What controls the PCM's instructions to the EGR
valve for voltage? Could I have a faulty PCM? What about bad upper intake
manifold and gaskets?
MW:
Mass airflow sensor if any could cause your no power problem. I have
never seen an EGR cause the problems you are having. Disconnecting the
EGR is just turning it off. IT will come on anytime you try to accelerate, so it
sounds like the EGR coming on as it should is just making your problem
worse, not causing the problem. Have fuel pressure checked, exhaust
backpressure checked. You can unplug the MAF and drive it to see if there
is a difference. Be sure EGR is plugged back in. EGR is not the cause of
your problem, but when it comes on, it makes it worse. If TPS failed, it
should have set a code.
VISITOR:
right on the money. 766.00 later with a new cat. converter in place runs like
a top. Thanks for all your help. I'll jump back on the site and throw some
green your way. Appreciate it.
Mileage = 97000
Engine size = 3.4L
dash lights = SES
codes = P0404; P0300
work done prior = None
work done to repair = Replaced fuel filter, fuel pressure regulator,
plugs, plug wires, air filter, and EGR valve. The EGR valve was replaced
after the service engine soon light came on. All other repairs were
made before the light came on but after symptoms started to appear.
tech = mw
question = The thing surges,sputters, and just flat runs bad. has no
power to pull itself up hills. If I drive it like there's an egg under
the gas pedal, I can run 80 mph on flat ground easily. Start up a grade
of any sort and it falls on it's face. Starting out from a dead stop is
an adventure too. That's where it does most of it's spitting and
sputtering. It has good exhaust flow and no rattling coming from the
catalytic converter. What am I missing here? Could a bad gas cap cause
this?
Could it be a bad PCM?
MW:
These conditions sure do sound like a plugged cat. converter. Placing your
hand over the tailpipe when revving engine when it has no power can be
misleading unless you have done it many times before, or can compare to a
car with the same engine. A backpressure test is the proper way to test
that. a plugged converter wil give lack of power on acceleration, misfire
codes, and egr position codes.
Aside from a plugged convertor, low fuel pressure can also cause this, but
not the EGR code. A plugged EGR passage to the intake will casue EGR
codes, but not misfire and no power.
Restricted injectors will missfires and no power, but not EGR codes.
Suggest having an exhaust backpressure test done.
VISITOR:
I forgot to mention that I was a tech for a bit over 12 years but drivability
wasn't one of my stronger suits. I have good exhaust flow. I unplugged the
EGR valve and test drove the car a short distance. The problem is still
there but not half as bad as it was. It is actually a lot better. Initial
acceleration is very acceptable now and will pull hills with very little problem.
Still thinking converter? What controls the PCM's instructions to the EGR
valve for voltage? Could I have a faulty PCM? What about bad upper intake
manifold and gaskets?
MW:
Mass airflow sensor if any could cause your no power problem. I have
never seen an EGR cause the problems you are having. Disconnecting the
EGR is just turning it off. IT will come on anytime you try to accelerate, so it
sounds like the EGR coming on as it should is just making your problem
worse, not causing the problem. Have fuel pressure checked, exhaust
backpressure checked. You can unplug the MAF and drive it to see if there
is a difference. Be sure EGR is plugged back in. EGR is not the cause of
your problem, but when it comes on, it makes it worse. If TPS failed, it
should have set a code.
VISITOR:
right on the money. 766.00 later with a new cat. converter in place runs like
a top. Thanks for all your help. I'll jump back on the site and throw some
green your way. Appreciate it.
Read my comment here (#39)
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