Fixed a Secondary System Vacuum Leak

[QB93Z]

We just got done with a plenum pull to locate a secondary vacuum system leak on George's (LT5-1935) recently purchased, 1990 ZR-1. Everything under the plenum was in excellent condition. All the tubing and fittings were tight. The leak was from the Secondary Actuator Valve. We repalced it with a new one and he was on the road in under an hour and a half.

He returned from the test drive with a big grin. :dancing :-D :razz: It was the first time he had really experienced the LT5 in full power mode.

BTW, the 1990 plenum pull is easier than the 1993, 1994 plenums I have done. There are less vacuum connections and electrical connections under the plenum.

Jim

[Aurora40]

You are turning into a regular ZR-1 shop! Nice work on the troubleshoot and repair. :) That's interesting about the ease of plenum pulling. Other than EGR, I thought the later ones had done away with that TB extension vacuum hose. And the ASR cars only have one throttle cable to disconnect.

What are the extra cables and such that the later cars have?

[QB93Z]

I should clarify. The plenums are easy to remove, but the 93-95 plenum is more of a pain to re-install because there are two more electrical connectors (one is for the Secondary Vacuum Sensor which on the 90-92 is over by the battery), and there is a hard plastic vacuum tubing that has to be plugged into a double connector deep in the valley. It pops out if you raise the plenum too high. The EGR line on the later LT5's is not too much of a problem since it is on the "outside" of the plenum.

I am practicing for Corvettes at Carlisle. I will pull the plenum on Darrin's 1990 ZR-1 and replace the plug wires, in the ZR-1 area of the Fun Field. I hope lots people attend so that we can have a good Q&A session and share under-the-plenum knowledge.

Jim

[FU]

Way to go Jim :thumbsup:

[secondchance]

"And there is a hard plastic vacuum tubing that has to be plugged into a double connector deep in the valley. It pops out if you raise the plenum too high."

I know which line you are talking about. I think it's actually PCV line.
When it pops out of the rubber boot best way I found is to crazy glue back into rubber boot deep in the valley first. Then after putting the plenum down, lift up the front, slide rubber hose back on to connection attached to the plenum and finally use a needle nosed plier to slip the metal clamp over the connection.
Another tip is to have replacement weather pack connectors on hand just in case you crack them while unplugging. Those things go real brittle sandwiched between the plenum and valley.:hello:

[QB93Z]

Most of the time its surprisingly simple to get the secondary on line isn't it.
that permagrin will wear off soon enough. next plenum pull will be porting ect.

Yes, when you first look under the plenum, it is very confusing, but after using the diagram and tracing it out, the Secondary Vacuum System is very straight forward.

I just wonder what the GM/Lotus engineering reasons were to put so many vacuum connections on the plenum and in so many different places. I would love to know if was just random or if there is really a purpose.

Jim

[LT5-1935]

Thanks again for all your HELP today Jim & Dave:worship: really appreciate your help and the way the car runs now.

Thanks Again :handshak: :cheers:

George

[QB93Z]

You are welcome my friend!

Jim

[ZZZZZR1]

Thanks again for all your today Jim & Dave:worship: really appreciate your help and the way the car runs now.

Thanks Again :handshak: :cheers:

George

Anytime!

It was lots of fun and always great to help another Z brother!

:cheers:

David

[tomtom72]

Darn, you guys have all the fun!:mrgreen:

Way to be Jim & Co.:thumbsup:

[XfireZ51]

Another tip: I don't disconnect the throttle cable.

[QB93Z]

Another tip: I don't disconnect the throttle cable.

I agree. Good tip. I put a padded cloth (a folded towel work great) on the driver's side of the windshield, covering the wiper arm. Then you can just flip the plenum over and set it upside-down.
http://i407.photobucket.com/albums/pp152/QB93Z/Misc/DSC01740.jpg


Jim

[Aurora40]

Ahh, I see that hose you mean. Yeah, on a '90 that comes out on the driver's side. Interesting about the throttle cables. The windshield is what I lean on though, when I'm standing on a tire and the alternator and trying to reach whatever the heck had me pulling it off in the first place. :)

If our cars didn't have clamshell hoods, I'd really have a hard time of it.

[XfireZ51]

Jim,

I rest the plenum up by the front of the wheel well. Like Bob I use the windshield for support. Also, I disconnect that hard line at the throttle body and then just slip it on fitting as one of the last things before I button things up. I put some sillicone sealer at bottom
of that hardline and the one next to it. In fact, I put a small coating of clear silicone gasket around all vacuum line junctions that usually have a tendency to pop out. Just a thin film to seal and hold in position.

[RICKYRJ1]

Great Job guys, Now that you mastered the plenum pull, time to step up to doing some P&P work. :mrgreen:

[Jeffvette]

Another tip: I don't disconnect the throttle cable.

It takes all of 2 minutes at most? Then you can get the plenum completely out of the way.

[QB93Z]

It takes all of 2 minutes at most? Then you can get the plenum completely out of the way.

Jeff,

Where do you disconnect it? And does it affect the setting of the throttle position sensor?

Thanks

Jim

[Jeffvette]

Jeff,

Where do you disconnect it? And does it affect the setting of the throttle position sensor?

Thanks

Jim

It does not affect the tps sensor. You undo the two clips that hold it onto the plenum, then hold the TB blades open either with something from the front of the motor, or the side and slide the cable off the linkage, and there is a retaining tab to keep the black plastic piece from sliding out as well.

[QB93Z]

Thanks Jeff, I will try that next time. It will make cleaning the plenum a lot easier as well.

Jim

[4DSZR1]

It does not affect the tps sensor. You undo the two clips that hold it onto the plenum, then hold the TB blades open either with something from the front of the motor, or the side and slide the cable off the linkage, and there is a retaining tab to keep the black plastic piece from sliding out as well.


That's what I did this weekend, three times..... don't ask :redface:

Anyway, its as easy as Jeff describes. I used a small screwdriver in from the side to hold the cable wheel in place, and then rotate the plastic piece out of the way and bingo out comes the cable end. I will add that the cable is held into the metal housing via clip, if you come in from the front of the housing with a very small screwdriver you can push in the clip (round hole about 1/8" dia) and the cable will slide loose. It's a fast and easy removal, once you do it. (took longer to type this up than removing the cable would take.

[Paul Workman]

I'm not w/o some mechanical ability, so given enough time, I can usually figure out a way. But, it is the practical stuff - the ways to do all the various mechanical things learned and shared by others that makes this board what it is...friggin' fantastic! (Like propping the throttle blades while removing the cables...duh!:thumbsup:)

Not to steal the thread - just "voicing" my gratitude for the "trail of bread crumbs" left by so many that have gone thru these cars before. They've BTDT, as it were, and are so willing to help others. For me it adds to the overall Z experience! :dancing

P.

[XfireZ51]

It does not affect the tps sensor. You undo the two clips that hold it onto the plenum, then hold the TB blades open either with something from the front of the motor, or the side and slide the cable off the linkage, and there is a retaining tab to keep the black plastic piece from sliding out as well.

Jeff,

Thanks. Hasn't really been an issue for my repairs so far, but next time I'll give your way a shot.

[QB93Z]

I'm not w/o some mechanical ability, so given enough time, I can usually figure out a way. But, it is the practical stuff - the ways to do all the various mechanical things learned and shared by others that makes this board what it is...friggin' fantastic! (Like propping the throttle blades while removing the cables...duh!:thumbsup:)

Not to steal the thread - just "voicing" my gratitude for the "trail of bread crumbs" left by so many that have gone thru these cars before. They've BTDT, as it were, and are so willing to help others. For me it adds to the overall Z experience! :dancing

P.

I don't consider it stealing the thread, so no problem. I agree with you completely. This forum is a valuable tool for my enjoyment of my ZR-1 hobby.

Jim