C4 Corvette Performance Verification

[Colton S.]

I'm taking my 1988 corvette for a pv. What are common things that have failed? What should I bring? Any tips are greatly appreciated, thanks.

[Patrick H.]

Re: C4 Corvette Performance Verification

Run it through many times.

Lack of preparation and being unfamiliar with the operations of the car are the things most likely to cause a failure. After that then you can talk about car parts that fail. If you know what's expected and how to work it, then the test should not be stressful.

[Terry M.]

Re: C4 Corvette Performance Verification

When I did PV in my 1970 (in the dark ages) I got a set of bulbs and fuses from Lectric Limited just to have the parts on hand in case of failure. At that time they sold "kits" with those replacement items. They were off shore parts and in the case of the fuses unsuitable for flight judging, but the convenience and comfort of having functional parts on hand as opposed to a run to the parts store outweighed the source. I don't know if they still offer these parts or if they have them for C4s, but i recommend a look see before the PV.

Full disclosure: I have no connection with this business and the same items may be available from other sources. I suggest doing a little bit of research.

[Floyd B.]

Re: C4 Corvette Performance Verification

C4's have complex electronics and a lot of circuits/wiring. I like Terry's advice. Fuses and bulb failures are common and easy to fix on the field. And as Patrick said, do the entire PVT as often as you can in weeks/days running up to the Regional. That said, here are some common trouble spots that should receive special attention to make sure they are operating correctly:

- HVAC system: C4's have a vacuum control module that controls the blend doors. It is behind the dash near the center. With age, these are prone to both electrical and mechanical failure. PV will check that the blend doors are working properly. Make sure you are very familiar with the operation of the HVAC system. READ YOUR OWNERS MANUAL.
- Horns: make sure both horns are working and they sound the correct note. If one of them seems a bit off, try disconnecting them one at a time so you can hear each in isolation.
- If your car has heated mirrors, it isn't uncommon for the wire to the heat element to create a short that causes the fuse to blow when turning on the rear window defroster.
- Speaker wire shorts: Use the balance and fade controls to make sure each speaker plays loud and clear.
- Alarm system: I'm not familiar with the '88 system but later C4's have a PASSIVE system and I find that many owners don't understand how it works. Read the Owners Manual and test all doors. Alarm switch failures for the doors isn't uncommon.
- Seat belts and latches: Make sure they "click", lock and release as new - no sloppiness. Make sure they retract quick and crisp - no remaining slack or need to hand feed them back into the housing.
- Antenna operation: All the way up when the radio is on. All the way down when the radio is off.
- Check all the radio features. Make sure the cassette deck works properly and sounds good. Check the auto reverse. It is common for old decks to spit the tape when it reaches the end.

There are tons of other potential trouble spots in these cars but these are the common ones I see and have encountered with my own car.

Have you contacted Tom Barr? He will be your best source of advice.

Good luck.

[Gary C.]

Re: C4 Corvette Performance Verification

Colton,

Ask Dave Perry, he's a GRRRREAT source about C4 PV's.

Gary
....

[Ed H.]

Re: C4 Corvette Performance Verification

I will add one more to Dave's advice. Make sure both Pass and driver door key operate as they should. In GM wisdom they designed a plastic clip that, in time, will crumble apart which negates the ability to lock and unlock either door. I found the Pass door item in the bottom of the door. A friend designed a brass unit, out of a small block that will never fail. My 93 ZR failed the lift on the rear hatch, and my 90 failed the door lock thingy twice. Between both cars I failed my C-4's PV's three times. The record for PV failures is in a C-1 at 7, the same car same owner, talk about a dreamer. Good luck in your effort!

[Colton S.]

Re: C4 Corvette Performance Verification

Thanks so much for the advice, its very well appreciated. We are going through the entire car once again tomorrow with the PV manual. It's made it through the last time we tested. I'm going to print off your suggestions and give to the guy going through my car, thanks again.

[Mark T.]

Re: C4 Corvette Performance Verification

Colton I suggest you also reach out to Tom Barr the team leader.
He is one of the best and will give you all the help you need
I would also suggest you get the PV manual from the NCRS store and as Pat suggested run through the test multiple times.
Good Luck
Mark

[Colton S.]

Re: C4 Corvette Performance Verification

Thank you, I've already purchased the PV manual, we are going to use it to go through the car tomorrow. I'll reach out to Tom Barr, thanks.

[Colton S.]

Re: C4 Corvette Performance Verification

I've rebuilt all the HVAC controls, speaker amps, and cassette deck I'm in college for electrical engineering so it all works as it should now . When I first bought the car I had no idea how to set the security system until my first NCRS meet. Needless to say they showed me how to set it. THanks for the advice, Yes I have contacted Tom Barr.

[Colton S.]

Re: C4 Corvette Performance Verification

When evaluating an item "pass or fail" for PV, I frame it this way: If you just paid the equivalent of a year's salary (about what a new Corvette has historically cost) drove it home 10 miles, anything that went wrong or annoyed you is going to have you returning to the dealer to get it fixed, is a failure. Squeaks, foam out the A/C vent, loose door panel, stiff lock mechanism, de-bonded console door cover that affects operation, etc. It doesn't have to be on the sheet to be a failure.

Remember that it is permissible to substitute new parts-store items like hatch lifters, wiper blades, belts, headlight bulbs, etc with no penalty. For PV preparation, it is wise to do so. Put the born-with items back on after the PV.

Here are some failure items that apply to your 88. Some of these were failures simply because they were overlooked during preparation:

> Hatch lifters. When "popped", the glass must rise on its own all the way to the top.
> Wipers. Driver side can't overlap the molding, they can't touch each other in the middle, and should park below the hood line. No Chatter. (See the FSM for details regarding dimensions and parking position. The FSM is "different" than some PV Judges assessment on what these dimensions and the parking position should be. Have your FSM available.)
> Be sure washer reservoir is full, and use the washers frequently during the wiper testing to reduce possibility of chatter.
> Sport Seat Lumbar. You have this covered.
> Spare tire inflation pressure. That the jack is free to work, and not rusted. Know where the lock lug nut tool is.
> Horn. Both notes work. Button operates in 12, 3, 6, 9 O-clock positions.
> Alarm. 3 switches activate the alarm: Each door and the hatch. Both door keys deactivate it. (Hatch switch can be sticky.)
> Rear cargo bin doors must latch without touching button. Just a gentle push to close and latch.

I can think of two "gotcha's" in an 88.

The solid state dome light timer. If it is currently working, it has certainly been replaced or repaired by now. There are electro-mechanical timers available that operate correctly, but improve reliability to 100% over the solid-state deal. If you have an OEM style solid state timer, don't leave the doors open so it doesn't overheat improving its life. I'd have a back-up plan for a PV.

Tom will check the ECM for trouble codes after the 10 mile drive. There is one code (Code 36) in an 88 that can be troublesome because it is intermittent, the SES is not illuminated until the next time the engine is started, but the code will be there when the ECM is checked. If you are not experiencing any codes or SES lights, you're fine. If you do get an occasional SES on engine start, and it is Code 36, start a new thread, and we'll go over it. I would not be comfortable taking an 88 to PV if it has an occasional Code 36, because it can rear its head at any time and will be a fail.

You'll do fine.

Where is the relay for the dome lights, I would like to look and see if its been replaced. I have the FSM I could check there also. Thanks, Dave.

[Colton S.]

Re: C4 Corvette Performance Verification

On the passenger side, above the carpeted hush panel, adjacent to the plastic box that the ECM mounts into. It is a black plastic box about 2 X 3 X 3/4" with an edge-card connector. 6 wires, (2) yel go into a single cavity. The box was secured to the main harness with masking tape, it is not mechanically fastened to anything. It can be tough to locate, it gets tight and dark up there.

I have a 1985 I purchased new. The timer burned out when it was a few years old but I didn't do anything about it. The first few months of 2006 I was prepping the car for a PV in September, and hadn't landed on a solution for the timer, which was NLA by then. I got in a client's 1997 Tahoe (no Remote Keyless Entry) to go to lunch and noticed the ctsy lights stayed on. When he turned the key on, they went out. I said "Turn the key off." He did, I opened the door, closed the door, key on, etc. His Tahoe behaved exactly the way my 85 was supposed to. I went to Chev and bought the timer relay and the pigtail and spliced it into my car. It is fully mechanical. It will never fail. I may be able to find the PN for you if you want to try to find an NOS Tahoe timer.

There are some inexpensive solid state timers available on timers.shop (That is the URL.) that could be used to trigger a normal 30A cube relay. You'll need some diodes and creativity to make it work as intended, but should be simple for an EE student. That's another way around the solid state timer.

Let me know if you need more.

Thanks for the info, I'm going to say that it was probably replaced sometime when it was new. It works too well without any problems (knock on wood, lol) Thanks again for the info.

[Ed H.]

Re: C4 Corvette Performance Verification

Colton, I had the honor of judging your car. I do not recall what part I judged but it is beautiful in all it's splendor, you should have no problem with your PV, just read the manual. Every item in the PV manual is also found in your owner's manual. Good luck, I will see you at Lakeland.

[Ed D.]

Re: C4 Corvette Performance Verification

Its been a while since I did mine, but the best advice anyone can give you, is drive it and test everything over and over again. You need to know your car as well as the judge, if not better. I drove my 72, 100 miles at night to the PV got it to the Regional for registration at 8:45 pm, Registration closed at 9pm, lots of Friday traffic. We did the PV fist thing in the morning. Past the first time out. Of course I had a patient, well qualified, terrific judge at the time, Terry McManmon.
Ed

[Colton S.]

Re: C4 Corvette Performance Verification

Dave, on a 1988, when the alarm system is set, triggered ( horn blowing ) should the car be able to start? How does the anti-theft system work in that way, I've read the PV manual but still have confusion. Thanks.