Check Engine Soon :(

[Patton]

Hey Fellas,

Just got back from over seas, stored vette (94 ZR1) by the book. She sat for 8 months and initially after I brought her out of hibernation there were no problems at all. Alittle sluggish at first but what woman wouldnt be after 8 months of neglect! So anyway, the problem started about a month after my return. The check engine soon light poped on, and limited my revs to 3000rpms. I went straight to a dealer and the dealer pulled these DTC's 0031 - CAM Sensor Circuit, 0056 - Secondary Inlet Valve, and 0061 - Port Throttle.
So, the mechanic tells me he is scared to death of LT5s and wont touch it any further, he was the resident vette expert. Is this something i can fix easily by maybe replacing a relay somewhere and this guy just didnt know it? Has anybody ealse experienced this problem?? The engine runs totally fine otherwise but I can definetly notice that it isnt at "full" and the 3k rpm limiter is very annoying but kind of nice now that milk is cheaper than gas. I went from 12mpg to 18mpg average. Any help would be greatly appreciated!!!

By the way, anybody know a mechanic in the Sacramento area that works on ZR1s?? If not I need to buy some books and have some serious studying to do before i go tearing plenums off and whatnot. Thanks abunch in advance!

[Jeffvette]

Feel like coming up to Portland.

I'll give you some tips when I get home from work.

[Bill]

Hey Patton, It looks like we are neighbors. :handshak: I'm in Elk Grove. I'm learning my LT5, I've had the plenum off a couple of times (2 to be exact). Maybe we should get together for a cup of coffee, and talk over our cars :blahblah:

Bill

[Jeffvette]

Here you go Patton.

Code 31, camshaft sensor. Do the basics. Check the wires for any pinching or nicks for false grounds. Unplug and look for any corrosion. Spray with some electronics cleaner and plug in. Clear codes and start again. Very rarely do these sensors go bad. But if you do wind up replacing them check to make sure the replacement has the same diameter as the original I have picked up a few that were not in spec.

Code 56 is a map sensor code. It's either seeing low voltage/low vacuum or high voltage/high vacuum. It can be set with a code 61 Secondary port throttle valve. More than likely on this it will boil down to a faulty actuator or vacuum hose/fitting.

[tccrab]

Patton:
I've just last week received the Helms manuals for my '90 ZR1. Be glad to help any way I can.
I'm in Folsom.
I should be around this weekend, maybe we can hook up.

Crabs

[Z Factor]

Hey Fellas,

Just got back from over seas

Welcome back, and thank you for your service. :handshak:




By the way, anybody know a mechanic in the Sacramento area that works on ZR1s??

This list might be able to help you.

http://www.zr1netregistry.com/ZR1_shops.htm#1

:cheers:

BTW- Let me suggest that you click on your User CP and put your location in the Edit Profile section. That way other ZR-1 owners will know your general location. :thumbsup:

[ShawnZR-1]

Wow, that sounds like what happend to mine earlier this year. On the advice of fellow members, I swapped the ECM out, it solved the problem.

When you have seemingly unrelated codes and errors pop up with only one common factor, it's likely the common factor.

Thanks for all of your service!

[Patton]

Jesus, how totally SCREWED would we LT5ers be with out this outstanding consolidation of experience and knowledge! Thank you very much for everybody's advice so far and I will try everything that was posted!

-Bill, KICKAZZ, I was really hoping somebody had another ZR1 around me! I am always in Elk Grove because my sister in law lives there. So hell yes we should hook up sometime, let me know whenever is good for you @ martinfr3@yahoo.com. Thanks for being so neighborly!

-Jeff, Thanks so much for the explanation of the codes and advice, Will do! As for the road trip, Portland is just a little out of my grasp at the moment, especially with her being "sick" and all right now, thanks much all the same!

-TCCrab Another neighbor!? How lucky can I get? Yes, the Helm, I have heard I need to get one! Thank you so much for the offer and hell yes I will take you up on it while I wait for mine (looking online for it). You can reach me at the aforementioned email addy.

Last but not least -Zfactor,
How’s it hanging buddy?? Long time no "type"! Still firing on all 8?
Thanks for the advice, and wilco.
As for the service part, it was my duty and pleasure! I signed up before 9/11. :thumbsup: Also, I can be recalled at any moment for four more years, in the Inactive Ready Reserve. So I’d like to enjoy my beast while I can!

[tccrab]

Patton:

Looks like the '94 model year Helms manual and ZR1 suppliment is out of stock. :cry:
They have a '93 with LT5 suppliment, but I suspect that there's minor differences between the two years.
Here's a link for the '93 set.
http://tinyurl.com/dxw58

Regards,

TomC
'90ZR1

[Z Factor]

Last but not least -Zfactor,
How’s it hanging buddy?? Long time no "type"! Still firing on all 8?
Thanks for the advice, and wilco.
As for the service part, it was my duty and pleasure! I signed up before 9/11. :thumbsup: Also, I can be recalled at any moment for four more years, in the Inactive Ready Reserve. So I’d like to enjoy my beast while I can!

I am doing well thank you. Hurricane Katrina gave us some flooding and power outages, but nothing compared with the poor Gulf States. My ZR-1 was safe and sound in the garage and is running great :thumbsup:

I have two cousins who are Marine Aviators over there, and I am always thinking about our boys in harms way. So anytime I get a chance to pass on a simple thank you to those who are serving I do. It is the very least that everyone should do to support those who support us.

Hopefully you will be here for some time before having to return. Regardless of how long you are back home, enjoy your KOTH as much as possible.

:cheers:

[Patton]

Tom,
Thanks for the info! However at 105$ I'll wait for the exact one :) I signed up for notification of when it is available. There arent any other makers of this manual?

UPDATE:
I hear absolutely NOTHING coming from the vacuum pump. So I am going to troubleshoot that right now. Im gonna use a voltimeter on the connector to make sure it has current, look like there is a little bit of corrosion on it. Hopefully thats all that is wrong here, I am dredding a plenum removal. I have a Chilton CD that has a step by step guide for plenum removal that should prove essential. Also (I hate to do this) But a thread at corvette action center has proved VERY useful in diagnosing my problem here is the link http://www.corvetteactioncenter.com/forums/showthread.php?t=14272

Thanks again. Hey by the way anybody ever experience that 3000rpm limiter?

[Jeffvette]

There is a fuse for the secondary pump on the driver side fender well. It's a 10 amp I believe. Check there first to see if it's blown.

[Patton]

UPDATE,

The pump is for sure burned out. However there is a leak under the plenum somewhere as well... :mad:
I used the vacuum hand pump and brought it to 10hgs and watched it slowly fall, my spirits fell much faster! DAMN! I dont have the tools like a damn torque wrench or the literature needed for this job. I sure as hell dont have the money to pay somebody,... besides I want the satifaction! Anybody know where someone can get the plenum gaskets? and other such parts? Do they sell new vacuum harnesses? or will I have to rig a new one?
Oh and I used a voltimeter on the connecter to the pump and it read about 13/14 volts. so it was getting juice, Im sure the leak under the plenum made it run itself to death.
Anbody have any advice for someone taking a plenum off for the first time?? I have never even messed with a plenum/intake manifold before... LOL helluva car to learn on! Fvck it, Im goin in!

[Jeffvette]

www.whiteracingproducts.com has the gaskets and the vacuum hoses. You can still get the vacuum pump from GM.

Here is a write up to follow along with for the tear down.

http://www.pnwzr1.net/LT5_tear_down.htm

[Patton]

Jeff,
Thanks a million! Very useful! Im sure I will have many more questions to follow though :thumbsup:


Hey Patton, It looks like we are neighbors. I'm in Elk Grove. I'm learning my LT5, I've had the plenum off a couple of times (2 to be exact). Maybe we should get together for a cup of coffee, and talk over our cars

Bill
Bill,... Soooooo hows about that coffee whenever you have free time??? LMAO
Im sure you never want to see the underside of a plenum again but If you could help me out here I would be so very gratefull!!!!

[Bill]

Not a problem. I sent you an email. I guess I failed to tell you who I was, you sent it back, I sent it back to you. The plenum is not that bad of a job, just intimidating the first time. Very educational once you can see whats underneath. Refer to the email, after Tuesday will be good for me.

Bill :)

[Z Factor]

Anybody know where someone can get the plenum gaskets? and other such parts?


I DO NOT recommend using White Racing Products.

These companies along with others should have what you need.


https://www.partszoneonline.com/index.php

http://www.acsvette.com/gaskets.html

Good luck
:cheers:

[DDSLT5]

I DO NOT recommend using White Racing Products.

These companies along with others should have what you need.


https://www.partszoneonline.com/index.php

http://www.acsvette.com/gaskets.html

Good luck
:cheers:


Why are you bad-mouthing White Racing products on this forum? Kurt White has been a solid supporter of our hobby, and a member of the ZR-1 Net Registry. [-X

[Z Factor]

Why are you bad-mouthing White Racing products on this forum? Kurt White has been a solid supporter of our hobby, and a member of the ZR-1 Net Registry. [-X

You and I have different opinions regarding Kurt and his company. However, your characterization of my post is inaccurate. I did not "bad mouth" WRP, I simply said I did not recommend them, and gave alternative vendors to buy from.

If he is liked by you as a businessman, it is fine for you to say so, just as it is fine for me not to like his business practices. We are both entitled to our opinions, as is anyone else.

:cheers:

[Patton]

Bill,
I havent recieved any emails yet, I just sent one to you however, if you get it just hit reply so we can rule out any misspellings or such.

Thanks again!

oh and Zfactor, thanks much for the alternatives, the more the merrier!


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

[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!

[Jeffvette]

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 :thumbsup:

[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!

:thumbsup: 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.

:cheers:
Tom

[Patton]

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