1991 z28 305 tpi.I've look on other posts trying to find a direct answer here so maybe I can get one please about my egr valve. If I put a pump directly on the egr valve vacuum line and pump it up a little bit my egr valve works fine but loses its vacuum in a short period of time. Should the egr valve hold vacuum or is it designed to no hold it for long? Also anyone else know which line on the egr solenoid hook to the egr and with hooks to the tb vacuum line the upper or lower one?? Thanks

 

Post removed by me ,
OOps , My bad , my response was based on my experience with an 87 CCC carb 305 instead of the TPI being discussed .

 

There are two different types of EGR valves; negative and positive back pressure. AFAIK, TPI engines use a negative back pressure valve (mine does). This means that the valve needs to see exhaust pressure in order to hold vacuum (indefinitely).

According to the '87 FSM, if you connect a vacuum pump directly to the valve and apply vacuum, the valve diaphragm should move and the valve should hold vacuum for at least 20 seconds (the vacuum will bleed off).

From your description, it appears your EGR valve is operating correctly.

Edit: Looking at the '87 FSM, it looks like it doesn't matter which nipple on the solenoid is connected to the TB or the EGR. It's just a normally open electrical switch.

The EGR should be marked with either a "P" (positive) or an "N" (negative) that denotes the type of valve it is.

Are you having a check engine light or a smog inspection issue?