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  1. #16
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    also, don't rule out the Engine Coolant Temp sensor. i had a car that would run great for 15 minutes or so and then die. it would start right back up after a bit of cooling down time. plugged a scan tool up to it and the ECT was telling the computer that the coolant temp was like +450 degrees. $10 and 15 minutes of work and the car ran like a champ for several more years.

  2. #17
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    Wouldn't the gauges the mechanical and digtal would be incorrect with each other? Just a thought....


    Quote Originally Posted by Fast Freddie View Post
    also, don't rule out the Engine Coolant Temp sensor. i had a car that would run great for 15 minutes or so and then die. it would start right back up after a bit of cooling down time. plugged a scan tool up to it and the ECT was telling the computer that the coolant temp was like +450 degrees. $10 and 15 minutes of work and the car ran like a champ for several more years.

  3. #18
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    I do have the service manual and I will check it this week and look for on how to extract the information - My volts from the alternator are reading 14.9 volts - battery is fully charged but I still am having issues with the display flickering every so slightly.

  4. #19
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    the ECT sensor and the temp gauge sending unit are independent of each other.

  5. #20
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    Quote Originally Posted by Fast Freddie View Post
    the ECT sensor and the temp gauge sending unit are independent of each other.
    Leave to GM to give you something else to scream at!! LOL Where is that located? On the thermostat?

  6. #21
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    i don't have car here to verify, but look on the front of the engine below the throttle body.

  7. #22
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    Quote Originally Posted by Fast Freddie View Post
    i don't have car here to verify, but look on the front of the engine below the throttle body.
    OK I have installed the new ECT sensor and still falls on its butt - started the car cold - its 38 degrees outside - ran for 5 minutes - gauges were at 15.0 volts - cooling got to 70 degree's - oil temp was stating cold - oil pressure was great - it still seems rich - engine was at 900 RPM then it sort of ramps up to 1100 RPM then stalls like someone turned the ignition off - I will have to put a fuel gauge on it this weekend to visually check the fuel pressure - It really hate to have to replace the fuel pump - its located inside of the tank I believe - LOL

  8. #23
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    It runs for ten minutes then dies - It has a opti that's one year old - New ECT - New Coil - New ignition control module - Fuel pressure is at 40 before I start it - When its running gauge says 36 PSI - Dies and pressure goes back to 40 PSI from 36 PSI- When I bump the throttle while running it jumps the pressure to 45 PSI then when I let go it goes back down to 36 PSI. When not running it always goes to 40 PSI. Any Help?:

  9. #24
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    Quote Originally Posted by WhalePirot View Post
    Is the engine stumbling or idling unevenly before it quits?

    Check for fuel pressure rise when you just turn the key on. Surely it is as the car starts, but note the number. It will drop some when the car starts/idles when some FP is relieved from the engine's use and low fuel requirement. When you blip the throttle, the lower vacuum pulls less on the internal diaphragm, allowing higher pressure for more power. FP is set (not on stock cars) with the vacuum line off.

    Watch for pressure changes as the car dies; which happens first?It there is a vacuum loss, the regulator will richen the fuel mixture. I would also watch for it 'loading up'; too rich. Depending on the local temperature, the time frame you mention might be when the car goes into 'closed loop', bringing all the sensor inputs into the ECM. I still use a vacuum gauge as those indications are as valid today as ever.

    I am now, not quite sure why I paid all that dough for an adjustable FP regulator, as my chip is 'cut' for stock FP. Just $$ up in fumes! Lesson learned. I know some tuners like to mess with it, but............

    You may have a sensor failing, IF it quits as closed loop happens.

    This is an interesting read: http://www.fuelinjection.com/portinj.html

    It runs for ten minutes then dies - It has a opti that's one year old - New ECT - New Coil - New ignition control module - Fuel pressure is at 40 before I start it - When its running gauge says 36 PSI - Dies and pressure goes back to 40 PSI - When I bump the throttle while running it jumps the pressure to 45 PSI then when I let go it coes back down to 36 PSI. When not running it always goes to 40 PSI. Any Help?

  10. #25
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    Quote Originally Posted by gmjunkie View Post
    WAG's won't work!! You need a gage,92-96 needs 41-47 Lb's to run properly,much below that and they will run Poorly,30-35 some won't even Fart!! As far as revving to 3000 with out a load on it it could hit the rev limiter with out a problem!!What I'm talking about I've seen them run for 10-45 min. and the fuel pump just shut down!!I've had it happen to a few Corvettes through the years,but I've ran into it allot on Chevrolet and GMC trucks!!
    It runs for ten minutes then dies - It has 38,000 miles and a opti that's one year old - New ECT - New Coil - New ignition control module - Fuel pressure is at 40 before I start it - When its running gauge says 36 PSI - Dies and pressure goes back to 40 PSI - When I bump the throttle while running it jumps the pressure to 45 PSI then when I let go it coes back down to 36 PSI. When not running it always goes to 40 PSI. Any Help?

  11. #26
    Gone but not forgotten John Robinson's Avatar
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    Quote Originally Posted by corvetteguy1993 View Post
    OK its been awhile sorry for the slow response time - I have changed the ignition coil no luck - changed the ignition module - again no luck - car is running rich and it freakin cold out - when its warm out around 55 degree's it runs less than two minutes and quits - seams to be running rich - I guess I better pull out the old pressure gauge and hook it up?
    Throttle Position Sensor (TPS)
    Copied from 1993 Service Manual
    The Throttle Position sensor (TPS) is a potentiometer connected to the throttle shaft on the throttle body. It is a potentiometer with one end connected to 5 volts from the ECM and the other to ECM ground. A third wire is connected to the ECM to measure the voltage from the TP sensor. As the throttle valve angle is changed (accelerator pedal moved), the voltage output of the TP sensor also changes. At a closed throttle position, the voltage output of the TP sensor is low (approximately .5 volt). As the throttle valve opens, the output voltage should be approximately 5 volts.

    By monitoring the output voltage from the TP sensor, the ECM can determine fuel delivery based on throttle valve angle (driver demand). A broken or loose TP sensor can cause intermittent burst of fuel from the injectors and cause an unstable idle, because the ECM detects the throttle is moving.

    If the TP sensor circuit is open, the ECM will set a DTC 22. If the TP sensor circuit is shorted a DTC 21 will be set. A problem in any of the TP sensor circuits will set either a DTC 21 or 22. Once a DTC is set, the ECM will use a default value for TP sensor, and some vehicle performance will return.

    A personal note, when my TPS failed it DID NOT set a code other than to tell me the ECM was bad.

    I know it's probably not this but what have you got to lose by checking it.

    [IMG]file:///C:/DOCUME~1/Owner/LOCALS~1/Temp/msohtmlclip1/01/clip_image002.jpg[/IMG]

  12. #27
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    Quote Originally Posted by John Robinson View Post
    Throttle Position Sensor (TPS)



    Copied from 1993 Service Manual


    The Throttle Position sensor (TPS) is a potentiometer connected to the throttle shaft on the throttle body. It is a potentiometer with one end connected to 5 volts from the ECM and the other to ECM ground. A third wire is connected to the ECM to measure the voltage from the TP sensor. As the throttle valve angle is changed (accelerator pedal moved), the voltage output of the TP sensor also changes. At a closed throttle position, the voltage output of the TP sensor is low (approximately .5 volt). As the throttle valve opens, the output voltage should be approximately 5 volts.

    By monitoring the output voltage from the TP sensor, the ECM can determine fuel delivery based on throttle valve angle (driver demand). A broken or loose TP sensor can cause intermittent burst of fuel from the injectors and cause an unstable idle, because the ECM detects the throttle is moving.

    If the TP sensor circuit is open, the ECM will set a DTC 22. If the TP sensor circuit is shorted a DTC 21 will be set. A problem in any of the TP sensor circuits will set either a DTC 21 or 22. Once a DTC is set, the ECM will use a default value for TP sensor, and some vehicle performance will return.

    A personal note, when my TPS failed it DID NOT set a code other than to tell me the ECM was bad.

    I know it's probably not this but what have you got to lose by checking it.

    [IMG]file:///C:/DOCUME~1/Owner/LOCALS~1/Temp/msohtmlclip1/01/clip_image002.jpg[/IMG]

    Well I replaced the TPS and no luck - I hooked up a timing light and started the car ran for two minutes and died. time light went off and now it won't start. Opti is little over two years old. You think it is the Opti?

  13. #28
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    It seems foolish to simply throw parts at the car.

    You need a good diagnostic tool. Either borrow or rent an AutoXray or buy a cable and TTS Datamaster and do a full log of what's happening and post a link to it and we can help. I have a suspicion it is dying when it goes from open loop to closed loop, but we can't tell without data.

    Perry

    Where are you located by the way?

  14. #29
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    Quote Originally Posted by pkincy View Post
    It seems foolish to simply throw parts at the car.

    You need a good diagnostic tool. Either borrow or rent an AutoXray or buy a cable and TTS Datamaster and do a full log of what's happening and post a link to it and we can help. I have a suspicion it is dying when it goes from open loop to closed loop, but we can't tell without data.

    Perry

    Where are you located by the way?
    Im located outside of St. Louis by Scott Air Force Base. I checked the opti cable and it seems fine - It's just a guess - But the usual senerio start it up, it runs for two minutes and timing light blinks away like crazy - stalls - then I turn the motor over and no timing light at all. I think it is opti. at this point and the nearest dealer is less than a mile but LOL it will die by then. Plugs were done when the opti was done last - plug wires are original - I tried to see if I could see any spark issues at night but no luck.

  15. #30
    Gone but not forgotten John Robinson's Avatar
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    Try this before you go to the dealer and get soaked for another opti. Get a can of carb cleaner and remove the air cleaner from the throttle body. After the car dies spray some carb cleaner in the throat of the throttle body while you have someone turn the engine over. If it fires you can eliminate the opti because you have spark and that is cheaper then a dealer will charge. Once you have done this and if the car starts you can then move on to the fuel pump. Seriously though if you can get it to start you need to pull the codes to see what is happening. You might try doing a search here for how to pull the codes yourself with a paper clip. Good luck and keep us informed what you find.

    If you get the car to restart try pulling the wire off the trottle position sensor to see if it keeps running.

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