89 idle issue

Discussion in 'C4 Forum' started by Steve Fontaine, Jul 19, 2017.

  1. Leadfoot33

    Leadfoot33 New Member

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    my dads 93 LT1 had an issue where it would barely idle, had to clean out the IAC sensor/valve. not sure if the L98 has the same but id assume so and start there.
     
  2. theboss

    theboss Well-Known Member

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    Hi Steve. About your low voltage, get someone in the car, pu t it in drive, take a voltmeter and take a reading directly at the big wire at the alternator, very often I see .2 or more difference, make sure you groud the voltemeter on the alternator housing. Next, still with your meter grounded on the alternator check the voltage at the battery (car still on drive), the difference might be around .1 volt. If idle is to low, alternator wont charge as much. Do this test at normal operating temp. If I would have to check this car, i would clean mass air flow, throttle body and if your car is equip with a IAC motor, I would remove it to be clean + the passages. Next would to check for vacuum leaks. Make sure you do a good road test after cleaning, left over of cleaner can enrich the mixture and fool you on the result.
    I am away from the shop and no access to shopkey website, I will get back to you next week.

    Good luck

    Stephane
     
    #22 theboss, Aug 11, 2017
    Last edited: Aug 11, 2017
  3. Steve Fontaine

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    ive also found a piece of info that interests me. i was looking up possible causes on google and one forum post with the same issue said that his gas filler cap was clogged and creating a vacuum.

    not sure why this didnt come to my mind before but my gas tank creates a crazy vacuum after driving for a bit. in fact the vacuum is so crazy that i literally park the car overnight and fill it in the morning. thats the only time i can fuel it up without there being a vacuum.

    the guy also said that taking the cap apart and cleaning the clog fixed his problem.

    also as stephane mentions, i have a feeling there are things in this vette that need cleaning. the guy that owned it before only put 4000km on it in 10 years. and it basically sat around for the rest of the time. he did have the basic maintenance done and i have all the records from when it was first bought by the original owner. i didnt see anything in the history about any real cleaning of things. just general tire stuff and oil changes.

    ill check the gas cap when i get a chance later today.
     
  4. Steve Fontaine

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    ive also have gone through the paperwork for the vette. seems as though it hasnt really been serviced since 2008.

    so therefore rather than risking driving it anywhere (not that i have been),, i am going to park it and do some work on it from now on. better to have a vette that works and just need a bit of fixing than to drive it until its dead. theres no way ill ever to be able to afford another vette so im dam well going to take care of this one.

    i guess i will start by cleaning the exterior and protecting it. cleaning the interior and protecting it. then i will move towards the engine and clean the crap out of it inside and out. ive only just noticed the engine bay is very dirty. cant imagine whats build up inside the engine. ill also be replacing whatever needs replacing. i want to also polish up and make the engine all shiny and snazzy. like a show car. right now it looks like its been sitting outside in the weather for 10 years.

    not sure what ill do with the paint. has aa touch of sun damage and has a few chips on the front. also has those light scratches from people washing it like a donkey would. that drives me nuts.

    so this will probably be the start of a video series on bringing an 89 vette up to car show quality.

    i dont like things that dont work right. it drives me nuts. and i will fix them come hell or high water

    let the fun begin...... tomorrow morning
     
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  5. Rruuff Day

    Rruuff Day
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    We will be following along Steve. :thumbs:
     
  6. Black 03 Z06

    Black 03 Z06 High RPM Poster

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    Steve, no doubt you will accomplish your goals. Great to have you here to post the technical issues that I am sure you are not alone with.

    Good luck to you and as Eric says we will be following along.:thumbs:
     
  7. Steve Fontaine

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    Before i start this journey, is there anyone in edmonton who has a code reader that will work on an 89?
     
  8. ddgermann

    ddgermann Active Member

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    IMG_6079.JPG I have this one. Should work on 90s and up.
    I will be home 1 day on the 26th before I head to work. You can pick it up and use it if you want.

    Product Detail

    Derek
     
    #28 ddgermann, Aug 14, 2017 at 4:23 PM
    Last edited: Aug 14, 2017 at 4:29 PM
  9. Riley P

    Riley P
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  10. ddgermann

    ddgermann Active Member

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    Yes apparently it does.

    "Does the Scan Tool work on OBD1 vehicles?
    Yes. The Scan Tool will work on selected OBD1 vehicles (Ford, GM, Chrysler and Toyota). In order to read OBD1 vehicles, OBD1 adapter kit 3129 is required. You also have the option to purchase the adapters individually. To view the adapters you will need to select your model number tool under OBD 2 diagnostic tools and click on the accessories tab."

    This was a pretty decent reader when I bought it a few years ago to diagnose an wheel sensor on my 13 Z06.
    Ended up putting on a new hub.... lol could have saved the money as the reader couldn't change the hub. ?!?!
    :Spit:
    D

    Oh just read what I posted... "adaptor".
    Doh!

    This 89 corvette should be OBD2 no? Steve?
     
  11. Steve Fontaine

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    i had heard about this paper clip things before but was skeptical. Turns out even a code reader for OBD1 reader does mostly the same thing as a bloody paperclip does. it makes the engine light blink...... glad I used a paperclip and saved myself another bunch of $$$

    to get the code definitions i went and downloaded the manual for a GM OBD1 reader for the vettes correct year. again saved $$$$

    im gunna take my hat off to stephane.... the only code coming up after 12 was.......

    CODE 36 DEFINITION BELOW

    -Mass air flow (MAF) sensor - burn-off circuit problem


    -Transmission shift problem (electronically controlled
    transmissions only)

    -Direct ignition system (DIS) fault - loss of 24X signal or
    extra or missing pulses in electronic spark timing (EST)
    signal

    -Ignition system fault - loss of High Resolution Pulse
    signal

    the others seem to be sub issues of code 36 from what i can tell. but im pretty sure its the mass air flow. that engine is DIRTY. i dont have time to go take it apart now and the battery went pretty low getting the code. i sat there for 10 minutes and also had the radio going without the car running. so of course it turns over and sputters out.

    ill make videos as soon as i can but it may be a few days. work is stupid busy lately.
     
  12. Steve Fontaine

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    i also just realized the burnoff circuit is a different part. anyhoo.... ill be checking that and replacing as needed.

    im glad parts for this vette are all over the place
     
  13. Steve Fontaine

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    Also just found this gem of information.


    i like the bolded red part best
     
  14. Steve Fontaine

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    Ok guys, i need help with this one.... i cleaned the MAF sensor and the vette started without problem. the idle is steady and the battery is better but not perfect. ill get to that later.

    after driving it around the block and letting it idle a bit. i gave it a few revs. now i noticed before a bit of smoke coming from under the hood after being driven a few times. but not all the time. after testing out the clean sensor...... i noticed the source of the smoke. this one is beyond me. exhaust, oil leak, i have no idea but i do have a dam clear video of the source and its a good thing i was recording so you guys can see.

    i hope this isnt a major thing. im getting tired of doing nothing but fixing it.

     
  15. Steve Fontaine

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    ive taken a closer look and its coming from part of the exhaust pipes. possibly when i went over a bump in the road and smacked the underside. i do remember that happening once. and i cringed when it happened. but what is leaking out of the pipe and is it safe to drive till it gets patched? it only does it when i hammer the throttle or rev it up a lot. or drive like a 13 year old in grand theft auto. (joking.... its more like a 20 year old)
     
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  16. Steve Fontaine

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    well i took it out for a quick gentle drive to see if cleaning the sensor kept up its gusto. and a big fail. that and the leak under the vette now has it doing the same things as before. rough idle, dropping battery voltage. smoke from underneath. so im gunna park it and save money over the winter.
     
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  17. theboss

    theboss Well-Known Member

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    I wonder if the catalytic converter is partially block, this could get you a low vacuum (rough, pour idle) and get real hot when you hammer it. Hard to see if it only smoke because of temperature or if a liquid is leaking on it.
     
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  18. Steve Fontaine

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    im going to take a bit of a break. trouble shooting this vette for half the summer is getting tedious. when i come back, ill have a more HD video. but please feel free to send thoughts on this issue. i will still follow this thread.
     
  19. ddgermann

    ddgermann Active Member

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    That's actually a pretty clever thought. :Hurray:
    Makes good sense. There seemed to be quite a bit of smoke in that leak. Like somethings burning....
     
  20. MikeysZ06

    MikeysZ06 High RPM Poster

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    Yeah,stepping back might be a good idea. I think most of us can sense your frustration Steve. Myself,I would've given up in July. Sure give you an "atta boy" though for your perseverance.
     
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