1993 Corvette, any issues, opinions? Options

[rpoz-29]

Yeah, tis one would start and idle pretty well when cold. Cold start injector, maybe? Once under load all hell breaks loose. Still pondering my next move.

[mr.beachcomber]

These Vettes didn't have a cold start injector (1988 was the last year). The ECM controlled the mixture while in open loop and it was fairly rich. Once the system went closed loop, the idle mixture was controlled by the ECM using inputs from the MAP sensor, throttle position sensor, idle control valve, oxygen sensors, and temperature sensors for both the coolant and the air inside the intake.

If the car idles poorly in closed loop, look for a vacuum leak if the mixture is too lean or a faulty idle control valve if the engine hunts for an idle rpm. They usually get gunked up over a period of time from oil mist in the throttle body/intake. You can clean it with carb cleaner if you're careful not to get the spray inside the electrical container.

Hope this helps. (IMG:http://www.frrax.com/rrforum/style_emoticons/default/beerchug.gif)

[rpoz-29]

It idles pretty well, but once under load it hardly runs at all. Once up to temp, the idle is not real good either.

[CrashTestDummy]

I’d still bet the BIG problem is the gas. The crap they force us to buy now is marginal right out of the pump. Give it a week, or two just sitting there, and it’s starting to turn on you.

I’ve quit that pump crap in all but our DDs. Everything but the diesel and race car get VP C9, but we have room for storage, and a VP dealer about 10 miles away. I don’t want to ruin another fuel system!

But I digress......

[rpoz-29]

Imagine the carnage after over 10 years. She took it to a dealer, (OMG!), who found it had no fuel pressure. They replaced the pump and strainer, drained the old fuel, and charged her a little over $1,000. I'm still tempted.

[mr.beachcomber]

Imagine the carnage after over 10 years. She took it to a dealer, (OMG!), who found it had no fuel pressure. They replaced the pump and strainer, drained the old fuel, and charged her a little over $1,000. I'm still tempted.

Before you go the dealer route, check your fuel pressure by tapping into the Schrader valve on the fuel rails. Turn on the ignition to energize the fuel pump, but don't start the engine. You should see a fuel pressure reading of 43.5 psi (optimal) or a reading within the range of 38-46 psi. If the fuel pressure is off, it will affect the whole system. If your reading is too low, change the in-line fuel filter (underneath the Vette on the passenger side), and then retest.

If the fuel pump needs replacement, it's an easy job on the '93 Corvette. Remove the fuel filler door, remove the rubber tray gasket, and then remove the fuel sender/fuel pump assembly. I've done my '89 several times over the years. (The last time was because 10% ethanol fuel destroyed the ground wiring connection on the fuel sender. The replacement assembly I got from ZIP Corvette for good for E85 so I won't have that problem again.)

If the fuel pressure is within limits, the next suspect would be the injectors (providing there are no vacuum leaks detected). Try Techron fuel injection cleaner first by adding it to the fuel tank to see if that helps. If not, and you haven't discovered another reason for the hard start/idle, you'll need to remove the injectors and have them cleaned/rebuilt or exchanged for new ones. I like the Fuel Injection Connection for their parts and service.

Hope this gets you going!

[GCrites80s]

After having my 1991 Corvette, I don't know that I'll own another one. Those cars were seriously ahead of their time and the technology was just barely up to doing what they were doing. We didn't have the tiny microprocessors we have these days. And the cars really push the limits of the available technology at the time. There are several computers in there that all talk on a common data bus. And it's really interesting trying to troubleshoot things and track the flow of data between units. It's 10 lbs of crap in a 5 (or even 4.5) pound bag. Neat cars and I love driving them...but I don't think I'd do it again. (though I've always wanted an admiral blue ZR1).

3rd Gen really is like 8-bit and 4th Gen 16-bit, but what you're describing sounds like a 32X with the Sega CD attached

[trackbird]

After having my 1991 Corvette, I don't know that I'll own another one. Those cars were seriously ahead of their time and the technology was just barely up to doing what they were doing. We didn't have the tiny microprocessors we have these days. And the cars really push the limits of the available technology at the time. There are several computers in there that all talk on a common data bus. And it's really interesting trying to troubleshoot things and track the flow of data between units. It's 10 lbs of crap in a 5 (or even 4.5) pound bag. Neat cars and I love driving them...but I don't think I'd do it again. (though I've always wanted an admiral blue ZR1).

3rd Gen really is like 8-bit and 4th Gen 16-bit, but what you're describing sounds like a 32X with the Sega CD attached

The air conditioning was computerized, you could pull error codes out of the AC controls. The AC talked to the ECM, there's a body computer that handles lights, doors and the alarm stuff (and others I believe, this is off the top of my head). And I believe there was one more computer, but I'm drawing a blank on what it was and what it handled. I went through the system wiring diagrams really well when I tried to install a FAST XFI fuel injection computer in mine. I left the ECM running and pulled off the wires for the injectors and sensors and such and then moved the fuel pump relay wire over to the FAST system, etc. So I left the ECM operational enough to run the stuff in the car and moved the wires to the FAST for anything that needed coordinated with the fuel injection. It worked perfectly (besides some tuning issues that turned out to be a leaking intake manifold....dumb mistake on my part). I learned just how sophisticated it was when I got into the middle of that project.

[GCrites80s]

Are say, '84s and '85s like that as well?

[trackbird]

Are say, '84s and '85s like that as well?

I don't know if they are quite as bad. I know things seemed to get more advanced with each model year.

To give you an idea.... I could never figure out why I'd start the car and the AC would take a moment to blow on you. I found (in the service manual) that the car directs the air at the floor when you first start it and blows down there for a second so it wouldn't fog the windshield. We've all climbed in the car and had the blower come on and fog up the glass....this car was setup to prevent that by switching to the floor, turning on the blower, counting to 5 or 10 or whatever and moving it back to the settings you had selected.

[rpoz-29]

Imagine the carnage after over 10 years. She took it to a dealer, (OMG!), who found it had no fuel pressure. They replaced the pump and strainer, drained the old fuel, and charged her a little over $1,000. I'm still tempted.

Before you go the dealer route, check your fuel pressure by tapping into the Schrader valve on the fuel rails. Turn on the ignition to energize the fuel pump, but don't start the engine. You should see a fuel pressure reading of 43.5 psi (optimal) or a reading within the range of 38-46 psi. If the fuel pressure is off, it will affect the whole system. If your reading is too low, change the in-line fuel filter (underneath the Vette on the passenger side), and then retest.

If the fuel pump needs replacement, it's an easy job on the '93 Corvette. Remove the fuel filler door, remove the rubber tray gasket, and then remove the fuel sender/fuel pump assembly. I've done my '89 several times over the years. (The last time was because 10% ethanol fuel destroyed the ground wiring connection on the fuel sender. The replacement assembly I got from ZIP Corvette for good for E85 so I won't have that problem again.)

If the fuel pressure is within limits, the next suspect would be the injectors (providing there are no vacuum leaks detected). Try Techron fuel injection cleaner first by adding it to the fuel tank to see if that helps. If not, and you haven't discovered another reason for the hard start/idle, you'll need to remove the injectors and have them cleaned/rebuilt or exchanged for new ones. I like the Fuel Injection Connection for their parts and service.

Hope this gets you going!

The current owner already took it to a dealer. I've all but talked myself out of it. Once the fuel issue is fixed, there may still be an issue with the opti. I simply don't want to buy another project.