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1992 Chevy Corvette
10-12-2013, 02:11 PM
Post: #1
1992 Chevy Corvette
I have a 1992 Chevy Corvette with an OBD1 code of 16 for direct ignition system (DIS) fault in circuit. Any recommendations for the course of action to identify repair needed?
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10-12-2013, 09:04 PM
Post: #2
RE: 1992 Chevy Corvette
It's a rather primitive system by today's standards but I suspect the easy way would be to clear the codes by disconnecting both ECM fuses or the battery for a minute then see if it comes back.

That said, do you notice any drivability issues?

Since the car is near 20 years old and we are poking in the dark till you supply a bit more info let's also ask mileage, last full tune including a wire set, and that sort of history. Is the check engine light on at the moment or is this possibly an old code stuck in the ECM from a previous issue?

Recalling that year has the ignition pack mounted behind the front pulley with all the plug wires going under the engine, which means it's a chore to work on. There's also heat shields on the plug wire ends and if they fall off the heat gets to the wires eventually. OTOH, just with it's age you may want to consider changing all of the ignition parts with OEM just to go another 20 years.

Let us know how you make out or supply us more to go on.
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10-13-2013, 12:01 PM (This post was last modified: 10-13-2013 12:40 PM by Paul D.)
Post: #3
RE: 1992 Chevy Corvette
I disconnected the battery previously and the codes came back. There were actually two codes, one for this and one for the coolant sensor (code 14). I bought a new coolant sensor and replaced it, disconnected the battery and both codes came back after a short drive.

The car is not driven frequently, there are 57,000 original miles, and has not been tuned in quite a while (I have not tuned it up and I bought the car in 2006). There are no drivability issues but it does seem to use a lot of fuel.

I have decided to sell the car so I wanted to ensure it is in good shape to sell without spending a fortune.

I disconnected the battery previously and the codes came back. There were actually two codes, one for this and one for the coolant sensor (code 14). I bought a new coolant sensor and replaced it, disconnected the battery and both codes came back after a short drive.

The car is not driven frequently, there are 57,000 original miles, and has not been tuned in quite a while (I have not tuned it up and I bought the car in 2006). There are no drivability issues but it does seem to use a lot of fuel.

I have decided to sell the car so I wanted to ensure it is in good shape to sell without spending a fortune.
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10-13-2013, 12:54 PM (This post was last modified: 10-13-2013 01:01 PM by Rupe.)
Post: #4
RE: 1992 Chevy Corvette
It's hard to do a proper diagnosis by remote control, which is why we ask for as much input as you can supply to help guide your work.

In my 40 plus years of experience, cars that are not driven much tend to have almost the same issues that daily drivers have with the exception of things wearing out. The problems faced instead of parts wearing out are usually related to storage conditions... I.E. heat, dampness, mice, bugs, and the like. Well, that and just plain old age. (I work on a LOT of older cars)

All that said, there are two temp sensors. One is for the dash gauge and probably located on the side of the head. The other is usually by the T-stat up on top. That one has a "weather pack" connector with a rubber gasket. This is the one that usually goes bad and causes a code. The other has no connection to the ECM and can't set a code.

Soooo, thinking about storage conditions and old age it's likely this car has two problems, and also likely that a FULL TUNE UP will not go to waste. (just based on age of parts) The other may be related to poor grounds or possibly a close inspection of the harness will turn up damage from rodents chewing on things. Hard to say without being there.

As another consideration, perhaps you can find someone local with the ability to scan the systems instead of just showing codes. With the right scan tool they can read real time info such as the actual engine temp or possibly see a low voltage within the ignition primary circuit. Again, sounds like a lot of foot work but it could save lots of head scratching and could find a very simple solution for you.

One thing you might try before heading to the next level is going around to each harness connector with some dielectric grease. Pull each plug on and off a few times and lay a fresh coating on the contacts. Also do similar with any ground connections you can find. Poor connections can cause all sorts of intermittent bugs that are not easily found any other way.

BTW, it's a Corvette. If you are getting even close to 10 MPG around town I'd be jumping for joy.

Lets us know how you make out.
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10-13-2013, 01:47 PM
Post: #5
RE: 1992 Chevy Corvette
The sensor I changed is located on the front of the motor in the water pump housing and I did not find a sensor on or around the thermostat housing. No evidence of any rodent damage, car has always been garage kept. I think I will take your advise and have it put on the computer to provide a more comprehensive scan and diagnostic.

Thanks so much for your time and input.
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