I recently suspect the EGR not getting enough vacuum while in cruise mode causing a code 32 and pinging. What is the vacuum at idle on a stock 305 TBI? And what makes it open the egr valve at a crusing speed? THanks,
Adam

 

The EGR valve should be getting no vacuum at idle speeds. Connect a vacuum gauge to the line that connects the EGR solenoid to the valve. Slowly increase throttle and you should see a minimum of 5 Hg. Next reconnect the vacuum line to the valve and slowly increase throttle. Check the valve with your finger and see if it moves up. Let the throttle back down to idle and the valve should close.

Be sure to check the rest of the vacuum system. At idle it should read between 17-22 Hg with no fluctuations. The vacuum will drop when throttle is applied and should return to a steady 17-22 Hg. If it fluctuates check all vacuum lines for leaks. If all lines are good and it still fluctuates check the gasket between the throttle body and the intake for leaks.

 

I'm having EGR problems too. When I connect the vacuum gauge to the line from the solenoid to the valve, I get no vacuum and I'm not supposed to at idle, I know. But when I rev the engine (and keep it at a constant RPM) I get 20 Hg for a couple seconds and then the vacuum drops suddenly to 0 Hg. Is this normal?

 

I'm not sure about that. According to the trusty Chiltons manual: Pg. 4-5

"A Thermal Vacuum Switch (TVS) or vacuum control solenoid may sometimes be used in combination with the EGR valve. The TVS will close off vacuum during cold operation. A vacuum control solenoid uses Pulse Width Modulation (PWM) to turn the solenoid ON and OFF numerous times a second and varies the amount of ON time (pulse width) to vary the amount of ported vacuum supplied to the EGR valve."

I made a quick video of my EGR vacuum...

EGR vacuum

* Thank you www.putfile.com *

 

Dude... a video posted on your second message on the board?

Awesome. Worthy!

Welcome to TGO. I don't have anything to add to the thread, mainly b/c I know jack about the EGR vacuum system on a TBI but I did want to say howdy.

 

I said before that the vacuum gauge read 20 Hg while holding at around 2500 RPM (that's a guess, my tach is screwy) but then the vacuum went to 0 Hg a second later. Well I discovered that if I have the MAP disconnected, the vacuum stays at 20 Hg until releasing the throttle. Is this normal? Other than when I disconnected the MAP sensor for this reading I have had no MAP trouble code. I know the MAP sensor detects changes in manifold vacuum and is the only way the ECM has of knowing if the EGR is operating or not, so I know the EGR and the MAP are closely related, but something doesn't seem right about the vacuum situation with the MAP connected/disconnected. Any ideas?

Annihilator, I'm sorry for hi-jacking the post, but hopefully we'll both learn somethng here since our problems appear similar.

 

No problem :P I'm learning from the replies and your posts too, its all good.