Hope all are doing well. My 1990 5.7L under 8500 GVWR requires a Negative Backpressure (NEG) EGR valve according to my service manual. From what i can tell, a mechanic installed a PORT EGR valve on my truck 10+ years ago which leaks down when vacuum is applied. Anyone have any insight on this or know where I can buy a NEG EGR? Rockauto sells POS and PORT (no markings). GMPartsGiant doesn't even list an available EGR valve for a 1990 5.7L. ACDelco website indicates a POS EGR valve as the correct one for my truck. I'm guessing NEG EGR valves are no longer made , but am confused and would be interested to find one and try it out. Preemptive response...No, I dont want to block it off and gain 1,000HP
POS/NEG/PORT EGR Valve
- Thread starter studigggs
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Steven Petersen
I'm Awesome
I bought this NOS one off EBay. Same part number as what show in my 88 parts catalog and also on the valve it replaced. It is negative back pressure. 1990 is most likely the same.
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Frank Enstein
Best. Day. EVER!
Whoever told you you would gain 1000 horsepower should be punched in the nose! Pulling the EGR off will give you 2000 HP and increase the fuel economy so much you will have to stop every 200 miles to drain the fuel tank.
Some people...
My '88 VIN K Automatic trans got a replacement EGR valve from O'Reilly's last summer. It was whatever they listed for my truck in their catalog--EGV628. The '627 is for manual trans.
https://www.oreillyauto.com/detail/.../chevrolet/k1500-pickup-4wd?q=egr+Valve&pos=0
The Negative back pressure valve, and the ported should both hold vacuum. A Positive back pressure valve won't hold vacuum unless there's enough back pressure in the exhaust to close the bleed valve.
I'm still getting the EGR code 32, when it warms up outside, I'll be looking into the EGR solenoid and wiring.
https://www.oreillyauto.com/detail/.../chevrolet/k1500-pickup-4wd?q=egr+Valve&pos=0
The Negative back pressure valve, and the ported should both hold vacuum. A Positive back pressure valve won't hold vacuum unless there's enough back pressure in the exhaust to close the bleed valve.
I'm still getting the EGR code 32, when it warms up outside, I'll be looking into the EGR solenoid and wiring.
OK, good to know the EGV627/28 are NEG. I guess what threw me was the note in the service manual that said POS and NEG valves would always be labeled as such and PORT valves have no indicating markings. Should have known the aftermarket wouldnt follow those rules. What also gets me is RockAuto claims the same ACDelco EGR valve can be used for K1500 and K3500 trucks in 1990 (ACD Part# 2141432) and the picture of that EGR clearly states "POS". I ordered the GM Genuine (2145073) which was the only one in the list that clarified "under 8500 GVWR Emissions", which I would assume means Negative pressure.
Steven Petersen
I'm Awesome
The proper Delco valve will have an N for negative stamped on it. The new AC Delco crap is made in communist China and shouldn’t be trusted.
I purchased 2 EGRs from RockAuto. ACDELCO 2141432 (Professional) is the version that ships with a host of different size washers. I sent that one back. GM GENUINE 2145073 (OEM) was a few $ more, but did not have the mix of washers. Made in China stamped on it. NEITHER of these AC Delco units had "N" stamped on it which has me confused. Ended up installing the "OEM" one. Guess I'll watch eBay for a new old stock to become available.
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