HELP! Connection from Plenum to EGR

[AlabamaDan]

When you take the throttle body off you can see what appears to be a hole to carry air to the EGR. Mine appears to be full of caked up, hard as a rock, stuff. Should it just be an empty passage? Should I simply clean it out (I'll have to use a screwdriver or something)?

[Q451990]

Typical carbon build-up. Happy scraping... get some BG Throttle body cleaner or Brake Parts Cleaner to make it easier.

Heath

[Q45tech]

This hole carries exhaust gases into plenum to mix with incoming air.EGR only works at steady cruise rpm/speed [1665-3300 rpm] after the coolant has warmed up.

This 10% EGR dilutes the normal 23% oxygen in air to ~~20% in plenum.

[qship96]

so if it remains blocked,how does it change power,performance,mileage,etc?

[Q451990]

Among other things (I assume) The EGR system helps reduce detonation (spark knock) by introducting exhaust gas into the combustion chamber.... so when it's not working, you're more likely to have spark knock. Spark knock, when detected by the knock sensors, will cause the ECU to retard the timing advance - reducing the power output of the engine.

There are several pages of symptoms listed in your FSM related to EGR valve failure.

Heath

[AlabamaDan]

We cleaned it all out, took lots of "suitable tools". Changed spark plugs, cleaned throttle body, this EGR passage, replaced vacumn hose that had a hole in it and replaced the valve cover gaskets. (Jeff Williams rocks!) Runs MUCH better.
Modified by AlabamaDan at 10:56 AM 7/2/2007

[Q451990]

Excellent! One weird thing that I noticed on my old Q... and I wonder if anyone could explain it to me. If I disconnected the EGR solenoid (or it wasn't working for some reason) I got a slight "clunk" from the differential at very low speeds right before stopping. Hooked it back up, and the clunk went away... Weird huh?

Heath

[Q45tech]

EGR was one of the first cruise fuel economy systems added to engines in the 1960's. The exhaust pressure reduces the pumping friction losses from the almost closed throttle at steady speed.

Some articles say that up to 10% of highway economy is directly atributable to EGR...................for sure it is more than 3-5% at 60 mph.

A reduced flow or blocked system is throwing gasoline money away.

Not to mention the failure of Nox on emission test!

Easy to tell who does mostly steady highway vs mostly city [where egr never flows much].

[AlabamaDan]

Good info Q45tech. Thanks.

BTW, when we cleaned it we did it dry as it crumbled and didn't drip crap into the heads since the valve cover was off. Used a screwdriver from both ends, a shop vac and finally a little brush that I use to clean my handgun with.