I just failed a smog pre-test and had a question. At what point does a large cam keep the EGR valve from working. My car failed the EGR test but I'm trying to figure out why. My cam is a 511/533 228/236 113lsa and I have 13 inches of vacuum at idle and around 20 cruising. I 'm also running 5psi boost.
It was running way rich at idle and a little rich at 2400 rpm, But I think with tuning I can lean it out enough to pass. I'm also using siemans 72# injectors which I know have a tendency for a rich idle. I guess my question is what can I do to get the EGR working and I'll try to use tunercat to lean the motor up.

 

How did they do "the EGR test?" Did they measure NOx, or did they scan the PCM for an EGR code?

 

I'm not in an enhanced area, So he just did the test at idle and pulled off the vacuum line and hooked up his vacuum tester and pumped it a few times which should slow the idle down or kill the motor but it did nothing on my car. I tried this test on my sons stock 94 Z28 and it does slow the idle a little so I guess thats what he's looking for.

 

Whoah, hold on there. He hooked up a hand vacuum pump to the vacuum fitting on the EGR valve and tried to pump it up to cause the idle to slow down??

Can't do it that way.

MANY MANY late model EGR valves have built in vacuum bleeds in the valve that absolutely renders a "bench test" like this with a hand vacuum pump worthless. You can't draw enough volume through a hand vacuum pump to keep the valve open- it'll immediately bleed back down.

Want proof? OK, go to the local parts store and ask for an EGR valve for a 1992 5.0L V8 TBI engine in a Camaro. Included with the valve will be instructions. On the instruction sheet it will specifically say that a bench test using a hand vacuum pump can not be performed on this type of valve. It only works on a RUNNING engine. (And beleive me I tried- I didn't beleive what I was reading but it was absolutely true)

Maybe LT-1 valves are different (stock or aftermarket), but I suspect there is a good possibility that's your problem.

Regardless, if your EGR valve is opening at idle (and you haven't intentionally defeated the system in some way with block-ed off passages) the idle WILL get rough and drop off some. Your little cam isn't anywhere near big engough to cause the EGR system not to work correctly. The fact that you have a blower on the engine also won't affect the EGR system.

 

I know the cam shouldn't be the problem, I've passed with a more radical one before. I haven't done any blocking of the EGR. When I built this motor I planned on running on the street and passing smog with it. The Blower should actually help pass smog.The smog tester also manually held in the diaphram on the EGR and it didn't affect idle at all or at higher rpms. I have an extra EGR valve so maybe I will swap it and see if it makes a difference and also check for any blockages. In my manual it says the car should stall while depressing the EGR diaphram.

 

Yes, the LT1 EGR valves are different than the ones used in the 3rd Gens. There is no vacuum bleedoff, and applying a vacuum to the EGR valve with a small hand pump (e.g. - Mitey Vac) will open the valve.