Question about 2003 Chevrolet Malibu
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Posted on Jan 02, 2017
SOURCE: power loss
Can't answer your last question but catalytic convertors that are just not working anymore won't cause any loss of power.
However, if they have shattered inside (they are kind of a ceramic honeycomb) they can dump junk into the exhaust system that can eventually clog your muffler or resonator.
Checking whether this has happened isn't difficult; after the warm up of the engine, either you or a helper needs to listen to the exhaust note. If firing of the cylinders is still distinct, the system isn't clogged with shrapnel; if it seems to hiss at higher RPMs, it is likely clogged.
This effect is easy to miss; I've had two failures and when cold, the engine would pull fine because the chunks of ceramic would fall to the bottom of the muffler and glue together somewhat. Once hot and agitated, they would clog the muffler and cause a severe loss of power but the idle would be OK. A hill that I would normally pull at 70 MPH, I couldn't top at all; had to sit and wait for things to cool down before proceeding.
It also seems some engines appreciate a bit of back-pressure in the exhaust system because the car gained in mileage and pulling power for several thousand miles before the clog became critical causing the mileage to fall sharply along with the power.
Posted on May 23, 2009
Turns out they should have put in a new fuel pump rather than the EGR valve. Hopefully this will solve the problem.
Posted on Jun 10, 2009
404 is exhaust gas recirculation circuit, and 405 is exhaust gas recirculation sensor circuit low. EGR sensor or ground?
Posted on Nov 13, 2009
SOURCE: I have a 2003 Chevrolet
P0404 - Exhaust Gas Recirculation Circuit Range/Performance
The EGR (Exhaust Gas Recirculation) system's purpose is to redirect exhaust gas back into the cylinders. Since exhaust gas is inert, it displaces oxygen and fuel, thereby lowering cylinder temps, which, in turn, lowers oxides of nitrogen emissions. For that reason it needs to be carefully metered into the cylinders (via the EGR valve) so as not to adversely affect the engine's performance. (Too much EGR and the engine won't idle).
If you have a P0404, then the EGR valve is likely an electrically controlled EGR valve instead of a vacuum controlled EGR valve. Also, the valve will usually have a feedback system built into it that informs the PCM (Powertrain Control Module) what position the valve is in; open, closed, or somewhere in between. The PCM needs to know this to determine whether or not the valve is operating as needed. If the PCM determines that the valve should be operating, but the feedback circuit shows that the valve is not open, this code will set. Or if the PCM determines the valve should be closed but the feedback signal indicates that the valve is open, this code will set.
Symptoms: There may be no symptoms of a P0404 DTC other than the MIL (malfunction indicator lamp) or check engine light. However, Exhaust Gas Recirculation systems are inherently problematic due to carbon buildup in the intake manifold, etc. This normal buildup can lodge in an EGR valve, holding it open when it should be closed. If this is the case, the engine may idle rough, or not at all. If the valve has failed and is NOT opening, then symptoms would be higher combustion temps and as a result, higher Nox emissions. But the latter symptoms aren't going to be noticeable to a driver.
Causes: Usually this code points to either carbon buildup or a bad EGR valve. However that doesn't rule out the following:
* Open or short in the 5 Volt reference circuit
* Open or short in the ground circuit
* Open or short in the PCM controlled voltage circuit
* Bad PCM (less likely)
1. Using a scan tool command the EGR valve to open while watching the actual EGR position (it will probably be labeled "desired EGR" or something similar). The actual EGR position should be very close to the "desired" EGR position. If it is, then the problem is likely intermittent. It may have been a lodged piece of carbon that has since dislodged, or it could be a bad EGR valve winding that intermittently opens or shorts as the valve temperature changes.
2. If the EGR "desired" position is not close to the "actual" position, then unplug the EGR sensor. Check for a good 5 Volt reference voltage to the connector. If it doesn't show a reference voltage, repair an open or short in the 5 Volt reference circuit.
3. If there is a 5 volt reference voltage, activate the EGR with the scanner, monitor the EGR ground circuit with a DVOM (Digital Volt/Ohm meter). It should indicate a good ground. If it doesn't then repair the ground circuit.
4. If there is a good ground, then check the control circuit. It should indicate voltage that varies according to the percentage that the EGR is open. As it's open more, the voltage should increase accordingly. If it does, then replace the EGR valve.
5. If the voltage doesn't increase incrementally, then repair open or short in EGR control circuit.
Try it and tell us news., Then, about other code...
P0420 - Catalyst System Efficiency Below Threshold (Bank 1)
The catalytic converter has an oxygen sensor in front and behind it. When the vehicle is warm and running in closed loop mode, the upstream oxygen sensor waveform reading should fluctuate. The downstream O2 sensor reading should be fairly steady. Typically the P0420 code triggers the Check Engine Light if the readings of the two sensors are similar. This is indicative of (among other things) a converter that is not working as efficiently as it should be (according to specs). It is part of the vehicle emissions system.
Symptoms: You will likely not notice any drivability problems, although there may be symptoms.
Causes: A code P0420 may mean that one or more of the following has happened:
* Leaded fuel was used where unleaded was called for
* An oxygen sensor is not reading (functioning) properly
* The engine coolant temperature sensor is not working properly
* Damaged or leaking exhaust manifold / catalytic converter / exhaust pipe
* Retarded spark timing
* The oxygen sensors in front and behind the converter are reporting too similar of readings
Possible Solutions: Some suggested steps for troubleshooting a P0420 error code include:
* Check for exhaust leaks at the manifold, pipes, catalytic converter. Repair as required.
* Use a scope to diagnose the oxygen sensor operation (Tip: The oxygen sensor in front of the catalytic converter normally has a fluctuating waveform. The waveform of the sensor behind the converter should be more steady).
* Inspect the downstream heated oxygen sensor (HO2), replace if necessary
* Replace the catalytic converter
One thing to note is that many vehicle manufacturers offer a longer warranty on emissions-related parts. So if you have a newer car but it's out of it's bumper-to-bumper warranty, there still may be warranty on this type of problem. Many manufacturers give a five year, unlimited mileage warranty on these items. It's worth checking into.
Basically you have any problem with the air system.
Keep us updated.
Posted on Sep 23, 2010
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