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ChevyTech · 07-24-2007, 10:57 AM

Keep in mind there are multiple types of EGR valves, and different flow rates.

With out having the service manual for the exact vehicle, I can’t say which vehicle has which type of EGR valve. Vehicle criteria such as, gross vehicle weight, auto / manual trans, “Tier 1” emissions / emissions system, engine size, model year and sometimes build date, all can make a difference in which type EGR system is on a vehicle.

The ECM and prom must be for the correct TYPE of EGR valve you are using.

Positive back pressure EGR valves - Should have a “P” after the last numbers on the valve. The pressure in the exhaust system effects (modulates) how much the valve opens.

Negative pressure EGR valves - Should have an “N” after the last numbers on the valve. The pressure in the exhaust system effects (modulates) how much the valve opens.

Port EGR Valves – The EGR solenoid pulses like a mixture control solenoid/fuel injector to control vacuum supply. Port valves have no “P” or “N” and it is blank after the last numbers on the valve.

The parts guy at the dealer may have no idea on what EGR valve to sell you.

07-24-2007, 10:57 AM	#7
ChevyTech Registered User Join Date: May 2004 Location: Minnesota Posts: 4,621	Re: 88 Blazer EGR issues Keep in mind there are multiple types of EGR valves, and different flow rates. With out having the service manual for the exact vehicle, I can’t say which vehicle has which type of EGR valve. Vehicle criteria such as, gross vehicle weight, auto / manual trans, “Tier 1” emissions / emissions system, engine size, model year and sometimes build date, all can make a difference in which type EGR system is on a vehicle. The ECM and prom must be for the correct TYPE of EGR valve you are using. Positive back pressure EGR valves - Should have a “P” after the last numbers on the valve. The pressure in the exhaust system effects (modulates) how much the valve opens. Negative pressure EGR valves - Should have an “N” after the last numbers on the valve. The pressure in the exhaust system effects (modulates) how much the valve opens. Port EGR Valves – The EGR solenoid pulses like a mixture control solenoid/fuel injector to control vacuum supply. Port valves have no “P” or “N” and it is blank after the last numbers on the valve. The parts guy at the dealer may have no idea on what EGR valve to sell you.