EGR Valve
02-16-2004, 09:05 PM
#1
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EGR Valve
Alright, so I'm gonna go for this first to see if it cures the problem of running rich, what exactly does it do? I read it can be deleted out of the PCM, true? Would it be better to just replace it or delete it out (if it can be done)?
02-16-2004, 10:19 PM
#2
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The EGR valve is used to control NO emissions. If your combustion chamber runs too hot, your car will produce excess NO emissions. The EGR valve mixes exhaust gas (no O2 as it has already been burned off) into the intake to dilute the O2 content in the combustion chamber, thus decreasing your Air/fuel ratio (run richer). This cools off combustion temperatures and would cause you to run richer. You can block off the feed tube (from your exhaust to the back of your intake) by taking a thin piece of sheet metal and cutting it to fit between your intake and the tube. You might throw a SES code for the EGR but you could see it that temporarily fixes your running rich issue; if it does, you know it's your EGR valve.
Old O2 sensors (they get coated with time) is definitely a cuplrit for running rich.
Old O2 sensors (they get coated with time) is definitely a cuplrit for running rich.
02-17-2004, 10:51 AM
#3
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The engine doesn't run "richer" when the EGR is activated. The recycled exhaust gas displaces oxygen, and quenches the combustion process, but the PCM knows the EGR is flowing, and adjusts the fuel accordingly. Intentionally running "rich" to control NOx would be counter-productive, since that would increase CO and HC.
The use of EGR does not hurt performance in any way, and in fact can help reduce the chance of detonation when lugging the engine at too low RPM in the wrong gear. If your EGR system is leaking, and flowing exhaust into the combustion chamber, its possible that it could cause a loss of fuel mileage, since in effect, you are losing engine displacement and will need more throttle for the same level of performance you would get without the EGR leak.
How do you know you are running rich? What symptoms do you have that lead you to this conclusion? Do you have any engine scan data or wideband O2 data?
"Deleting it out" of the PCM generally refers to altering the activation parameters or the diagnostic routine to eliminate the code/SES light that you get when you physically delete the system. To fully defeat it, including the impact of a leaking EGR valve, you would need to physically block the EGR source, as noted in the post above.
The use of EGR does not hurt performance in any way, and in fact can help reduce the chance of detonation when lugging the engine at too low RPM in the wrong gear. If your EGR system is leaking, and flowing exhaust into the combustion chamber, its possible that it could cause a loss of fuel mileage, since in effect, you are losing engine displacement and will need more throttle for the same level of performance you would get without the EGR leak.
How do you know you are running rich? What symptoms do you have that lead you to this conclusion? Do you have any engine scan data or wideband O2 data?
"Deleting it out" of the PCM generally refers to altering the activation parameters or the diagnostic routine to eliminate the code/SES light that you get when you physically delete the system. To fully defeat it, including the impact of a leaking EGR valve, you would need to physically block the EGR source, as noted in the post above.
02-17-2004, 04:04 PM
#4
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