Plenum Pull...Parts List Varification...

[| 1990 ZR-1 |]

I have a MY 90 with 33k miles. I'm having a similar issue as ZR1Man where I can't fill much of a differnece, if any, between Normal and Power settings. I do get a little bit of vibration and struggle as the RPM's rise with the Power Key on. The engine seems smoother with Normal setting, but the accellaration is the same in both settings. I already tested the secondary actuators per Marc H's instructions and they work fine. My assumption is that at WOT the secondary intakes open, and there's extra air going in, but not fuel. Please correct me if I'm wrong.

I belive the car is completely original under the plenum judging by the ammount of dirt and grime piled up in there over 21 years. I would like to pull the plenum and replace most of the serviceable items, and I wanted to verify the list I gathered from reading in different posts here.

1. New injectors qty 16 FIC or Accel
2. Gasket/Seal Kit (36pcs) from Jerry, Fuel Injector Maint, 90~92 (VITON)
3. Wire Set, Spark Plug, 90~95 [10D] form Jerry
4. Duralast/Ignition Coils from Autozone Part # DC-63
5. Ngk Ix Iridium/Spark Plug Part # BKR5EIX-11
6. Fuel Filter from Ecklers Part # GF652
7. Coolant and Oil Change

Am I missing anything? If anyone experienced any issues with the parts above or if you have a suggestion for better parts, please feel free to share.

I can't wait to feel the power of this beast once it's properly running. It feels quick at Normal setting, and to think how much faster it could be with the additional almost 200 hp is scary!!

As always, I greatly appreciate the help of this community.

-Gary

[Kevin]

just make sure you don't use dexcool for the coolant. i mean, unless you want to pop a head gasket...

[tomtom72]

Looking great with the list!

Just be sure that the coils are by application. I went with the AC Delco coils only because that coil type has a few applications. GM has a specific P/N for the LT5 coil due to it's placement on the motor.

The plugs are a personal choice. Remember that the 90's have flat seats in the plug holes and use a washer. You can use a taper seat, precious metal plug but you have to over T/Q it to create a tapered seat. I stuck with the AC Delco 41-602's as they are the replacement by application for the FR2LS's, flat seat w/washer.

This is just MHO.


Tom

Yes on the coolant 1825-M spec is the GM spec number, P/N 12378560. Use a GM T-stat also! If you have to buy other coolant, make sure on the label it says "Do Not Mix with DEXCOOL" or "Do Not Use in a cooling system requiring DEXCOOL." that's a dead give away that it's 1825-M GM spec coolant.

[QB93Z]

I suggest that you trouble shoot a secondary throttle vacuum system fault so that you know if you have to look for vacuum leaks when you have the plenum off.

Here is a link to zr1man's similar hread: http://zr1.net/forum/showthread.php?t=14438

There are a couple of common leak sources under the plenum. One is a check valve and the other is the Secondary Throttles Solenoid valve. It is easy to see if the check valve is leaking without pulling the plenum.

But first, verify that your vacuum pump is operational.

Jim

[tccrab]

Originally Posted by QB93Z

I suggest that you trouble shoot a secondary throttle vacuum system fault so that you know if you have to look for vacuum leaks when you have the plenum off.

Here is a link to zr1man's similar hread: http://zr1.net/forum/showthread.php?t=14438

There are a couple of common leak sources under the plenum. One is a check valve and the other is the Secondary Throttles Solenoid valve. It is easy to see if the check valve is leaking without pulling the plenum.

But first, verify that your vacuum pump is operational.

Jim

Further to this suggestion, here's a link that every ZR1 owner should have handy:
http://www.corvetteactioncenter.com/...diagnosis.html
Props to Rob of the Corvette Action Center for his comprehensive write up on the ZR1 secondary port system.

While you're in there cleaning and poking around, be sure to re-torque all the fasteners on the oil mist boxes and the injector housings. They tend to loosen with repeated temperature cycles.


TomC
'Crabs

[| 1990 ZR-1 |]

Originally Posted by tomtom72

Looking great with the list!

Just be sure that the coils are by application. I went with the AC Delco coils only because that coil type has a few applications. GM has a specific P/N for the LT5 coil due to it's placement on the motor.

The plugs are a personal choice. Remember that the 90's have flat seats in the plug holes and use a washer. You can use a taper seat, precious metal plug but you have to over T/Q it to create a tapered seat. I stuck with the AC Delco 41-602's as they are the replacement by application for the FR2LS's, flat seat w/washer.

This is just MHO.


Tom

Yes on the coolant 1825-M spec is the GM spec number, P/N 12378560. Use a GM T-stat also! If you have to buy other coolant, make sure on the label it says "Do Not Mix with DEXCOOL" or "Do Not Use in a cooling system requiring DEXCOOL." that's a dead give away that it's 1825-M GM spec coolant.

Thanks for the input Tom.
I see that Autozone sells the AC Delso 41-602 spark plugs, but how come they don't come up under the ZR-1 option?

Also, where can I buy the AC Delco coils? Are you sayind that theDuralst coils will not work on LT5?

[| 1990 ZR-1 |]

Originally Posted by tccrab

Further to this suggestion, here's a link that every ZR1 owner should have handy:
http://www.corvetteactioncenter.com/...diagnosis.html
Props to Rob of the Corvette Action Center for his comprehensive write up on the ZR1 secondary port While you're in there cleaning and poking around, be sure to re-torque all the fasteners on the oil mist boxes and the injector housings. They tend to loosen with repeated temperature cycles.


TomC
'Crabs

Jim and TomC.

I checked the vacum pump, and it works fine. I also hooked up a vacum pump to the vacum line going under the plenum, and pumped it to 10ng. The pressure held for a while, but did go down to zero over a period of 10 minutes. Also when turning on the ignition, the pump comes on for a few seconds than shuts off, but than after about 3-4 minutes pumps again for about a second. I think i have a slow vacum leak which probobly will not affect the operation of the secondary vavles as much, but I will certainly try to trace it and fix it while i'm under there. How long does the pressure normally hold for in a properly working system?

[mike100]

Originally Posted by | 1990 ZR-1 |

Jim and TomC.

I checked the vacuum pump, and it works fine. I also hooked up a vacum pump to the vacum line going under the plenum, and pumped it to 10ng. The pressure held for a while, but did go down to zero over a period of 10 minutes. Also when turning on the ignition, the pump comes on for a few seconds than shuts off, but than after about 3-4 minutes pumps again for about a second. I think i have a slow vacum leak which probobly will not affect the operation of the secondary vavles as much, but I will certainly try to trace it and fix it while i'm under there. How long does the pressure normally hold for in a properly working system?

my vac pump cycles a couple of times every min or two- I think that's normal...it actually leaks at the pump hose I think. All of my stuff was tip top, except for 1 vac line had popped off. On yours, perhaps the solenoid that runs the secondaries is stuffed, but at anyrate, you will be able to diagnose everything quite easily once you pull the thing apart.

Even though my problem was simple, further repairs included replacing the injectors. That really made it run a lot smoother.

I used the parts store non-platinum Ac plugs- they run fine. Since plugs are so easy to change on the LT5, I decided against exoticly expensive ones...plus I wanted as close to the factory heat range for emissions testing.

Don't know about the coils, never replaced anything on mine..pretty standard GM part though.

A bad injector coil will manifest itself as a miss when warm, but your original problems sounds like an issue with the secondary injector relay or something electrical with the driver.

[| 1990 ZR-1 |]

Given that I only have 33k miles on the car, do I really need to replace the wires and the coils? Do they go bad due to age or miliage or both? I don't really have any missfiring issues, but I figured since I'll be under there already, might as well replace everythign that could potentially give me trouble down the line.

[tomtom72]

Gary, I'm not saying that your choice of coils is incorrect. Rather, the issue as I see it is that type of coil has a few GM applications. GM lists two coil types for a waste spark application, ours specifically and then another coil P/N for all the other GM applications. Upon closer reading one finds that "all others" live in the open air, ours live under the plenum & have a different P/N. My conclusion is that ours live in a more severe environment therefore they must be constructed to tolerate the conditions.

Also, a long time ago it was popular to use Screaming Demon Coils for the extra juice. The long term issues that I observed was that the failure rate was higher than the OE coils. Is there a correlation? I don't know. I just feel it is worth mentioning as a fwiw. I had Accels in my car for 3 yrs and they didn't miss a beat, I switched them out the the correct GM ones because the Accels had other applications besides an LT5. My thought was are these built to survive under the plenum and can be used in other applications; or is the LT5 application the "other" or "also fits" application?


Tom