85 Vette

[Dave R]

Bought an '85 C4 this past Christmas for my wife. Beautiful car, 51k original miles, sat in the garage for 20 years. New brakes, tires and a tune-up. She idles at 53-56 but after warming up 30 mins or so has a tendency to stall. Replaced all vacuum hoses and pcv valves. Runs better but still have the same issue. Am going to attempt replacing the egr valve and have researched the forum. Have noticed that in doing so I'll need to remove the plenum. If I do this do I need to drain the coolant?

 

[MacMulkin Chevrolet]

Welcome to the Corvette Action Center!

 

[Rob]

Welcome to the Corvette Action Center.

I'm going to move your thread into the C4 Tech Forum for greater exposure.

 

[DonB]

Welcome to the forum. Drain it down about a gallon or so. That should be sufficient, because you'll have to remove the t'stat housing and upper hose. Gives you more room to work without leaks. How much vacuum is it pulling at idle, Hot and cold?

 

[Dave R]

Welcome to the forum. Drain it down about a gallon or so. That should be sufficient, because you'll have to remove the t'stat housing and upper hose. Gives you more room to work without leaks. How much vacuum is it pulling at idle, Hot and cold?

I haven't tested the vacuum yet, was told by a mechanic the egr was bad. Thanks for the input. Any other advise is highly appreciated.

 

[DaveP85C4]

Why don't you check the fuel pressure first? Watch it when it dies. Does the pressure begin to fall before it dies? My 85 did this, and it was the fuel pump. If the stalling is concurrent with the electric fan coming on, it could be the lower system voltage with the fan on causes the pump to slow down too much to deliver adequate fuel.

The EGR valve is easy to diagnosis with the factory service manual. It has several "modes". If it's closed at idle and remains closed, it is not the cause of the stalling.

There is no coolant in the plenum or runners. Why mess with the thermostat housing for a plenum removal?