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1995 Lesabre - EGR Valve


tken35
07-21-2013, 01:22 AM
I was wondering if anyone could provide a simple explanation as to why each EGR valve is specific to only certain models/years?

I wanted to save a few $$, so I went to an auto recycler and after receiving an interparts exchange report, I couldn't locate any of the corresponding GM models/years.

Interestingly, what I did notice was that several other GM models/years have what seen to be identical looking EGR valves (at least on the outside).

Would any of these work?

Thank you in advance.

Blue Bowtie
07-21-2013, 07:35 AM
The rate of exhaust gas flow required for each engine varies. The EGR valve on your engine is an electronic stepper motor, and it includes a feedback signal (slidewire) to notify the PCM of its position. There is no method for the system to report EGR flow however, and only a crude calculation based upon RPM, throttle position, and MAP are used to verify whether the EGR is leaking or plugged.

Since the pintle size and shape, and port opening size can vary among EGGR valves for different engines, 50% open on a Buick 231 may mean 6 CFM flow while 50% open on a 350 SBC may mean 14 CFM flow. As you can see, the SBC valve would probably stall the Buick engine at 50% opening, and the opening rate is the only thing the PCM can control. Conversely, a Chevy 191 V6 EGR valve at 50% might only flow 4 CFM. so it would starve the Buick.

Is your current valve inoperative, or is it possibly just plugged? EGR codes don't always mean the valve itself is the problem.

tken35
07-21-2013, 10:34 AM
Blue,

Thank you for the great explanation! The codes that were previously retrieved were P0401 and P1402.

We cleaned and scraped the carbon deposits as best as we could and for about 3 weeks the car ran like a champ. The highway mpg went back up to 25 (it had fallen to about 20 mpg but it usually averages 26-27 mpg).

This past week the engine light turned on again and the mpg dropped back to to about 20. The code we retrieved was P1402.

Btw, I have used the STP Throttle Body and Air Intake cleaner in the past to dissolve carbon deposits, but I have never been that impressed. Is there an another product on the market that works better at removing carbon deposits?

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