Check Engine Soon :(

[Chedberg]

Here is the website with a wonderful how-to for removing the plenum, coil packs, and starter. Bookmark it now!!

http://www.bcvettes.org/

Click on "How To" on the left and away you go.

When you are putting everything back together, make sure you get the 12 plenum bolts tightened to 19 or 20 ft/lbs! Just using the hatch removal tool, we had white smoke coming out of the tailpipes because coolant was seeping into the cylinders. A torque wrench is a very useful thing to have around, get one! You can use it to tighten all of the bolts with the exception of #4 and #6 unless you can fab something together, it is a tight fit.

We were able to re-use our plenum gaskets. When you are ready to lift the plenum off, use a utility knife and a flat-head to lift up on the gaskets, if you are patient they will come out A-OK. Get a set of replacements, no telling if you need them until you do.

[Patton]

Thanks Much Chedberg,
Good advice about the torque wrench, I found a write up on taking the plenum off in the Chilton manual... They have all the ftlb requirments for every bolt and I purchased two torque wrenches, one from 0-80 pounds and the other from 20-200. Only 40$ for both, couldnt pass it up!
I also found extenders and narrow sockets at a locla hardware store that enable access to 4 and 6. Thanks again!

Remember to up the torque a little bit when you use the extenders, as the shaft actually flexes under torque.

[RedZR]

You can "rebuild" the vacuum harness by simply changing the check valve out- the valve is a generic part that you can buy at NAPA. Also, if you are lucky you can install the same check valve where the vacuum line goes into the plenum on the drivers side. It will act the same as the valve that's bad in the harness.

Disconnect that hose, plug it and then apply the vacuum to see if it leaks. If it holds your little check valve is bad- easy fix.

Write if you need additional info- I have done this before.
Dan



P.S. Check this shyt out... just got a quote from a local dealer.... UGH... And the vacuum harness isnt even listed there because GM doesnt make it anymore. Im gonna use burger king straws and duck tape for my new vacuum harness. If you cant Duck it,... FVCK IT!!

Part Numbers (all NET prices)
1996743 - Actuator = 93.21 each
10067563 - Resevoir = 18.76
1997222 - Valve ASM = 35.27
10098474 - Pump ASM = 245.46
10067759 - TB Gasket = 4.49
10168680 - Gasket = 30.14 (plenum port)
10168682 - Gasket = 31.81 (plenum starboard)
10110908 - Crankcase breather hoses = 12.03 each[/QUOTE]

[Patton]

check valve,.... huh? I have no check valve i guess... There is just a little rubber coupler where you say the valve should be... And another thing, when I connect my vacuum hand pump to the hose running under the plenum and turn the motor on, the vacuum rises and holds at about 17-18hgs... Yet with the engine off It wont hold the vacuum. 17-18 hgs isnt enough to function the actuators??

[tomtom72]

Hi Patton,
Thanks for your service!

I'm a rookie Z driver so I don't have much knowledge but when you get a Helm & read about the vacuum system for the secondaries it will explain this:
The pump is only supposed to charge the system &/or maintain 12"Hg in reserve tank and goes off at 17"Hg.
When the motor fires the engine vacuum takes the place of the pump. That is why you got a good vacuum reading with the motor running and when it was off the vacuum test showed a falling reading due to a leak in the system.
The check valve RedZR is talking about is one he added as a backup/or replacement for the OE one in the system. Great idea! I looked on my parts CD and can't find the one that is supposed to be there so I think it is intergral with the vacuum hose assembly and the Helm says there is one in the pump??? I'm probably wrong but I know I looked & can't find it.
I don't know if this helps but the diagnostic chart in my 90 Helm says to use 20"Hg as a diagnostic benchmark to test system integreity.

Sorry I can't come up with a better insight but I thought this might help.
Tom

[Patton]

Thanks alot tom,... I am just waiting for the damn parts to get here! I ordered over a week ago and havent heard anything. Once they do I'll pop the top, replace everything and let you guys know what happens.

Interesting note: I removed the burned out pump and plugged the hose with a golf tee. Then ran the car and I no longer get the check engine soon and 3000rpm limiter during normal operation like I got before,... However, when I punch it with the key in "full"- Right when I normally expect Mr. Spock to make it so, The service engine soonlight pops on with no power change good or bad, and then I immidiately backed off and the service light went off almost as fast as it came on. Then I turned the key to normal and after several spirited 150mph sprints (at NORMAL power was still FAST and strong!) I am begining to understand why it was so bad before, I think the pump was a HUGE leak in the system and plugging that leak I think proved what I was feeling before, the system had a slow leak that the pump had to work very hard at compensating for which led to its demize, so sure I think I could pop another pump in and it would be fine for a while until it burned out again... Basically I just confirmed what I had diagnosed.

One last question that Im sure is elementary but I just havent learned it, How do you reset the DTCs?

Thanks!

[tomtom72]

Hi Patton, Seems like you have the handle on the situation! On the DTC codes, Jeffvette, Kevin or on of the other long time drivers knows the magic trick. Me I just do what Gordon says in the book, remove + battery terminal for more than 30 sec. At least I think that is what GK's book says. The book's in the car & I've never had a code to reset!

Hope your stuff gets there quickly. I just got on pkg, vacuum hose, 2 actuators & vacuum tank. Oh the check valve is part of the vacuum hose assembly and the Helm says there is one in the pump. Waiting on the solenoid valve and crank case hoses and etc.


Tom

[Patton]

Hey tom, where did you get your vacuum hose assembly from?