Secondaries not opening

[lakemeadzmonster]

After all of my under plenum repairs ext. I just got back from an after rush hour highway drive and I go to Full Power and my secondaries don't engage at all.

I feel a slight hesitation and then a check engine light, as soon as I go back to normal light goes out and car runs better than ever,

I looked at the obvious plenum tube routing and I think its something else I probably knocked something loose. Any quick checks outside of the plenum? Thanks "The beat goes on"

[Kevin]

it's a vacuum leak

[sammy]

do you have a scan tool .?is it code 61? when you just turn the key to on what does the vacume pump do ??

[Paul Workman]

Marc Haibeck wrote a great article. "Verifying Secondary Actuator Operation with the Plenum in Place", available on his web page.

Below is a schematic of the vacuum circuit for the secondaries and HVAC:



Marc's article goes into detail, but it doesn't mention the possibility of the accordion snorkel tube between the air cleaner and the air horn collapsing; which it may well be doing at WOT IF either you don't have a Semco tube, or the wire hoops that Marc provides to support the tube, or a sleeve inserted inside of the tube to support it (and also smooth the air flow!).

Overview: The vacuum pump provides initial vacuum to the vacuum reservoir, but mainly provides vacuum for the secondaries under extended WOT periods. Once the engine is running, the plenum provides all necessary vacuum to maintain the actuator reservoir, during normal driving.

Upon snapping the throttle open, it is the secondary port throttle valve solenoid (#4 on the schematic) that opens and the reservoir provides the initial vacuum to pull the throttle plates open. Then if plenum vacuum is too low to hold the secondaries open, the vacuum pump will kick on and sustain the actuators. So, IF the vacuum pump does shut off (doesn't run continuously) then the system integrity - up to the solenoid - is good enough. (Refer to Marc's article for further troubleshooting of the actuators, etc.)

If the pump does not shut off, then a there is a leak or the plenum check valve is bad, or the pump is not working. Disconnecting the line at the rubber connector as the vacuum line goes under the plenum and holding your thumb over the vacuum pump line should result in the pump shutting off in a second or two. If not, then the pump may be bad, or there is a leak somewhere.



OR you could just take all the secondary crapola out and be done with it and it's problems forever...but that is another topic.

Gotta run, but this should give you a place to start. Be back later to see how ya get along.

P.

[batchman]

Originally Posted by lakemeadzmonster

Any quick checks outside of the plenum?

Every time (so far - knock on wood!) when I've had secondary problems it's been the cars way of telling me that the battery connection has loosened. Here's hoping that's your issue, the symptoms have always been just as you described.

Good luck,
- Jeff