Hey,

i checked my egr solenoid today with a hand vacuum pump.
Jumped the A and B Terminal of the ALDL and turned ignition on.
I took a vacuum of 12 inHg from the vaccum harness of the egr solenoid to/from the manifold side.
It showed not a real stable vacuum. Within 20 seconds the gauge went down from 12 to 11 inHg.

Is it still in spec? Tolerance? Or should I replace it?
The test gauge and handpump is 100% sealed and ok.

Car is a 1987 Firebird Formula with the 305tpi.
Greetings,

Chris

 

Don't have the service manual handy, but while you got things opened up to replace the EGR, you might consider doing some other things while you have access. have a good look at your fuel injectors if they are original multi-techs - they go out just from age. fuel pressure reg, and look close to see if you have anything leaking in that area, there are fuel line o-rings that can get old. I had mine far enough apart due to a few bad injectors that I decided to change valve seals too. This was at 64K miles. The intakes were in great shape, but the exhaust all but gone. It more time consuming, if you can afford the down time, its worth it knowing you have a freshened up top end.

 

Thanks for your reply.
The top end from the LB9 is in good working condition, all valve stem seals were changed 2 years ago.
Injectors (ohm) are ok. Fuel pressure regulator was not tested, but the engine runs strong. Injector o rings were replaced, the intake manifold gasket also.
Everything is fine, I just wanted to check the solenoid with my Haynes check instructions, the books says: "It should be able to hold the pressure." No tolerance, no time, nothing.

But for the solenoid test I dont have to open things up. EGR Valve is new AcDelco part too.

 

Sounds like your in good shape then! I'd venture a guess that if it can hold vac for a few minutes I wouldn't worry about it until you get a service light. I'm guessing that it usually only needs to hold vac for a small period of time, which it sounds like it is doing. since its the only thing you have to worry about, thats a lot of work to get down in there. some guys say they can do it with just the plenum off, but I don't see how.

 

But when it looses vacuum, it is leaking and let air in. So its not optimal for AFR.
Im thinking of replacing it.

 

You talking about the solenoid? It doesn't lose vacuum - it routes vacuum to the EGR valve or not. When it's "closed" the EGR valve vacuum supply is routed to a vent so the valve closes. 1 in/Hg in 20 seconds isn't enough of a leak to even make a measurable difference in the engine vacuum at idle with laboratory grade instrumentation. You would never be able to find it. You're WAY overthinking this. The valve is a simple plastic valve with a rubber seal - it's not going to be perfect and 20 seconds is basically ETERNITY as measured by the ECM that calculates at about 80 Hz.

And as far as AFR goes - that's what fuel trims (BLM and INT) were designed for. So the engine would be able to operate in it's imperfect world of cheap plastic consumer grade components. And in any case you will certainly find that your EGR solenoid is not impacting the trims anyway. Both should be 128. If they aren't look elsewhere for the cause.

There are WAY more important things to look at first if you are having vacuum leak symptoms. And if you aren't - why are you trying to fix something that isn't broken? Chances are that the original part will out-last any readily available Chinese replacement from the aftermarket. Leave it be.

GD