02 malibu bad acceleration after warm up

[wolfort]

02 Malibu V6 3100 engine
When the car is cold, it runs really smooth at idle and running.
The shift(1-2, 2-3 and 3-4) usually occurs at 2.2-2.7k rpm; shif is smooth.

However, after the car is warm up, it still idles very good.
But it is very difficult to accelerate and the shift becomes very poor.
The engine can hardly rev to above 2k rpm unless I push the gas pedal very hard. The rpm jumps when the it falls between 2k-3k.

Got misfire code 0302, 0300. I changed the wires, plugs, fuel filters, and clear the code. No more code for half month, but the problems still exist.

What could be possible reason?
One mechanic did a few test, including compression test, and told me the EGR might need replace, but he can't guanrrantee anything.
Could any one help me out? Thanks.

[wolfort]

Update:
I unpluged the electronic connector that linked to the EGR,
the engine light comes on as expected,
but the car runs like a dream.

Does this mean I need to change the EGR?
or I need to check something else, like MAP, that affect EGR performance?

Originally Posted by wolfort

02 Malibu V6 3100 engine
When the car is cold, it runs really smooth at idle and running.
The shift(1-2, 2-3 and 3-4) usually occurs at 2.2-2.7k rpm; shif is smooth.

However, after the car is warm up, it still idles very good.
But it is very difficult to accelerate and the shift becomes very poor.
The engine can hardly rev to above 2k rpm unless I push the gas pedal very hard. The rpm jumps when the it falls between 2k-3k.

Got misfire code 0302, 0300. I changed the wires, plugs, fuel filters, and clear the code. No more code for half month, but the problems still exist.

What could be possible reason?
One mechanic did a few test, including compression test, and told me the EGR might need replace, but he can't guanrrantee anything.
Could any one help me out? Thanks.

[J-Ri]

MAP would be my first check. You know from unplugging it (and since it's good cold) that it's not sticking open, which means it's being commanded open. MAP is a big factor in determining whether it should be on, I think TPS must also be below a certain percent.

[nealn]

Plugged catalytic converter. Driveability symptoms such as a drop in fuel economy, lack of high speed power, rough idle, stumbling between mid RPM ranges - ie 2,000 to 3,000 RPM or stalling are classic symptoms of excessive backpressure due to a plugged converter.

You can confirm this by checking vacuum and/or backpressure. To check using vacuum, connect a vacuum gauge to a vacuum port on the intake manifold. Start the engine and note the vacuum reading at idle. Increase RPM's to about 2,500 rpm and keep steady. Normal idle vacuum on most engines is around 18 to 22 inches Hg. When the engine speed is increased there should be a momentary drop in vacuum before it returns to within a couple of inches of the idle reading. If the vacuum reading is lower than normal and/or continues to drop as the engine runs, it probably indicates a buildup of backpressure in the exhaust.

Checking via backpressure is a bit more difficult. Ask if you want instructions.

If you live in the P.R.C. (People's Republic of California) an assembly containing the Catalytic converter, pipes at both ends and O2 sensor bungs = $300 off Flea Bay - it MUST be C.A.R.B. approved and list the most recent Executive Order - EO # - certification on the converter - this rule went into effect Jan 1, 2009. If your in the other 49 - the same assembly is around $140. IF you want to search out a 'universal' type converter for any of the 50 states - it must be a 3 way, ODB2 compliant, (CARB certified if for the P.R.C.) If you live in California, you will have a very difficult time getting anyone to ship you a converter.

Good luck

[wolfort]

Thanks all guys.
I found an independent garage, they tested TPS, MAP, they are OK.
They found the cata. converter low-pass and installed an universal one.
Total charge is $320 after tax, not cheap but acceptable!
Car is running great now!

BTW:
GM dealer is no nice at all. The cata. converter has 8year/80k warranty, my car is just over 80k.
but they will do nothing, even no discount on genuine part.
What a shame compared to other manufactures good-well program.

Originally Posted by nealn

Plugged catalytic converter. Driveability symptoms such as a drop in fuel economy, lack of high speed power, rough idle, stumbling between mid RPM ranges - ie 2,000 to 3,000 RPM or stalling are classic symptoms of excessive backpressure due to a plugged converter.

You can confirm this by checking vacuum and/or backpressure. To check using vacuum, connect a vacuum gauge to a vacuum port on the intake manifold. Start the engine and note the vacuum reading at idle. Increase RPM's to about 2,500 rpm and keep steady. Normal idle vacuum on most engines is around 18 to 22 inches Hg. When the engine speed is increased there should be a momentary drop in vacuum before it returns to within a couple of inches of the idle reading. If the vacuum reading is lower than normal and/or continues to drop as the engine runs, it probably indicates a buildup of backpressure in the exhaust.

Checking via backpressure is a bit more difficult. Ask if you want instructions.

If you live in the P.R.C. (People's Republic of California) an assembly containing the Catalytic converter, pipes at both ends and O2 sensor bungs = $300 off Flea Bay - it MUST be C.A.R.B. approved and list the most recent Executive Order - EO # - certification on the converter - this rule went into effect Jan 1, 2009. If your in the other 49 - the same assembly is around $140. IF you want to search out a 'universal' type converter for any of the 50 states - it must be a 3 way, ODB2 compliant, (CARB certified if for the P.R.C.) If you live in California, you will have a very difficult time getting anyone to ship you a converter.

Good luck