Hi all,

My Uncle just gave me his corvette, he is the greatest uncle in the world. But it has a little problem and I have never owned a vette before so I could really use some help.

Anyway it is a 1989 covertable with only 19.000 miles on it, however it has not been on the road since 1993. It has been stored inside and driven a few miles every once in a while. When I got it it was running real ruff but it started right up, I figured it was from the old gas. It had about 1/4 tank and I filled it up with new. It still ran real ruff so I put pluggs, distributor cap, and rotor. When I was done it would not start. I took the distributor back off because I figured I pinched a wire or something. Well it started and my wife took off with it right away. She shut it off at the store about 5 miles away and when she came out it would not start. I went and replaced both the coil and the spark module thinking it had to be that but it still didnt start. After a long while it just started up and I drove it home.

Now I find that when the engine is completly cold it starts and runns smoothe and full of power, after a mile or so when the temp gets up to running temp I start to loose power, it sputters and backfires a little and runns real ruff. If I shut it off it will not start again until it cools off.
I can start it at about 135 degrees but it will only idle, if I give it any gas it will dog out. If I let it cool all the way down it will start and run great again for a mile or so.

Any suggestion? One person told me the MAP sensor but I dont get any check engine lights and I would think the MAP sensor would throw a code???

Any Help would be great
Thanks
Dave

 

From the sounds of not being able to start the car after driving it and then cutting it off, you may have a problem with heat soaking of the starter. However, that's just one guess as you say it runs real rough when it heats up. If you've got the time, you should have your alternator checked to see if it's in proper working condition as well. I'll just stop there, as I'm sure someone else will come and give you other options which may be a lot better. Still you should consider checking your alternator. A shot alternator was a big problem of mine a few years back.

 

Sorry, I think I didnt write clear enough. When I say it will not start, I mean it turns over fine, but it will not fire at all. It just turns cranks and cranks and cranks

 

No hot start or long crank with an ok cold start or vice versa is usually the injectors. Check resistance across the injector terminals - should be about 16 ohms for each, hot or cold.

Try starting it with accelerator to the floor. That will signal the ECM to stop pulsing the injectors and if it starts, it usually means it was flooded from leaking injectors.

For starting, the fuel pump relay is activated by an ECM driver. If it's shot, the oil pressure switch will activate the relay once it gets about 4psi of pressure. A failed driver circuit can lead to long cranks on a hot engine, but it usually starts once the oil pressure builds. To check, just turn the key on and listen for the pump to run. Or hook up a fuel pressure gage and see if it has about 42 psi when you turn the key on. The pressure should remain steady and not fall (well at least not for a good 30 minutes or so). The relay is on the firewall, just to the right of the brake booster should you suspect that it's failing when hot.

 

Fuel pump does this too.I have had this experience plenty of times.

 

Check the 02 sensor. It sounds like you car runs great in open loop and as soon as you go into closed loop it runs like crap. In closed loop the engine adds fuel according to input from 02 sensor.
Cheap part that can make a world of a difference.

 

ya I thought of the o2 sensor at first also but it is a single wire sensor and someone told me that the single wire ones dont run open and closed loop.

Does anyone know if the single wire o2 sensor runs open and closed loop??

 

I believe single wire sensor is fine and what the car requires.

I believe dual wires sensors, second wire provides heat to the sensor if it is to far from exhausr outlet to stay warm.

If you have headers, I am sorry I didn't read everything you said, then you may need two wire

 

The O2 sensor is ignored in open loop.

 

Your car does run in open and closed loop! All OBD1 and OBD2 vehicles have both. Please probe your Assembly Line Diagnostic Link (ALDL) and see what codes are present! Do not depend on the "Check Engine" light to tell you if you have problems! Jumper terminals "A" & "B" together and watch your " Check Engine" light. It will flash in LONG and short pulses. Each code will flash three times and then it will go on to display the next code. The first code that you will ALWAYS see is a 12 code. (- ..) The 12 code will be followed by any additional codes that are stored OR it will go right into another series of 12 codes if no other codes are stored! Here are examples of how you will see the flashes as represented by dashes for long and periods for short.
33 code ( ... ... ), 14 code ( - .... ), 11 code ( - - )

To clear the codes, just disconnect the battery for about 2 minutes.


Please read and post all storred codes1

Bill

 

thanks for the info Bill, I just checked the codes and there are none, just fashes 12.

I did another check, I hooked 12 Vdc to terminial G which is the fuel pump check and the pump came on, I left this jumper and tried to start the car. It took awhile but after about 3 5 second attemps it started and ran good. I removed the jumper and drove around the block and it started running real ruff. I floored it and it just cut out on me. I made it back home ok but now will not start again. I dont have the energy to put the jumper back to see if it will start or not