260 V8 EGR revisited... or NOT the EGR?

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King_V

Master Mechanic
Jul 17, 2013
307
5
18
Sicklerville, NJ
I'm an idiot.

There, I said it.

Ok, so it turns out I *might* not have a problem with my EGR valve at all. Because I was trying to apply my 1974 knowledge to 1979.

I complained that the old EGR valve would not hold vacuum when I used a vacuum pump. Yeah, that might've been a great diagnostic tool on my 1974 Dodge. Not so much the 260 on my 1979 Cutlass.

I became suspicious when, just on a lark, I applied vacuum via the vacuum pump to my new EGR valve. Huh, doesn't hold vacuum either!

Then I researched, which I *should* have done previously, and found this link. Yeah, wish I'd done that earlier.


Ok, well, I still find it suspicious that the car is fine when it's NOT fully warmed up, but then when it hits fully-warmed-up temps, it will ping like hell with anything more than extremely light throttle under load (doesn't happen when in neutral, obviously).

I may or may not change the EGR valve. I know it's getting vacuum when warmed up, though I'll have to try with the 2000 RPM trick as mentioned in the article. Who knows, maybe the EGR valve IS bad.

1) If I *do* replace the valve, what's the proper way to clean out the passages?

2) What else could be causing it that would NOT be causing it when the car is warm but not completely warmed up? I really think it's happening when the thermal vacuum switches are letting vacuum to the distributor.
 
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