EGR

[srercrcr]

I pulled the EGR valve off my 78 Pontiac 301...it was super clogged up with carbon and the diaphram would't budge. Cleaned it up with carb cleaner, seems to be working now. That's 29 year old carbon!
By the way, I only had pinging occasionally so go figure.

 

[Uncletruck]

Yep, it's a good idea to clean the EGR valve up every 3 or 4 years. I've had them where carbon builds up on the valve seat, not allowing the valve to close all the way. This causes poor idle and hesitation on acceleration. It's usually hard to notice if it isn't opening, other than things getting a little hotter in the summer causing some detonation. Back in the old days before emissions tests, people would just disconnect the valve and retard the timing a bit to not have to bother with it, this was especially on pre-'75 cars that used dirty burning leaded gasoline that would mess the valve up frequently.
-Mark-