***Login to the Forum here ***

Support FSC and see no ads! - Click Here
Results 1 to 20 of 20

97 tahoe runs rich/misfires

This is a discussion on 97 tahoe runs rich/misfires within the Technical / Maintenance forums, part of the General Discussion category; I have a 1997 tahoe with a vortec 350...when i start it up in the morning it fires right up. ...

  1. #1
    Registered User 91chevyon22s's Avatar
    Join Date
    May 2008
    Location
    calgary, AB
    Posts
    26

    97 tahoe runs rich/misfires


    Support FSC and see no ads! - Click Here
    I have a 1997 tahoe with a vortec 350...when i start it up in the morning it fires right up. after about a minute or 2 of driving it misfires at idle, and if i shut it off and re-start the truck within the next 3 hours i have to actually give it a bit of gas just for it to start..it seems like it runs to rich when it idles.
    It has new cap,rotor,plugs,wires,coil,O2 sensor and fuel filter...please help me with this its really becoming irritating not to mention robbing gas milage like crazy !! thanks in advance

  2. #2
    Registered User 91chevyon22s's Avatar
    Join Date
    May 2008
    Location
    calgary, AB
    Posts
    26

    Re: 97 tahoe runs rich/misfires

    Bump...i really need help with this!!
    1997 2wd Tahoe,loaded,tinted,dropped,22's
    1995 2wd Suburban,tinted,2 12's, exhaust,roll pan, 7" touch screen
    1981 Short box,dropped 4/6, 468/th400, black on black
    1977 blazer 8" lift 454/4speed/205
    sittin on 38.5" swampers

  3. #3
    Hired Goon Aloicious's Avatar
    Join Date
    Mar 2007
    Location
    UT
    Age
    33
    Posts
    1,996

    Re: 97 tahoe runs rich/misfires

    Quote Originally Posted by 91chevyon22s
    I have a 1997 tahoe with a vortec 350...when i start it up in the morning it fires right up. after about a minute or 2 of driving it misfires at idle, and if i shut it off and re-start the truck within the next 3 hours i have to actually give it a bit of gas just for it to start..it seems like it runs to rich when it idles.
    It has new cap,rotor,plugs,wires,coil,O2 sensor and fuel filter...please help me with this its really becoming irritating not to mention robbing gas milage like crazy !! thanks in advance
    how do you know its running rich? lean conditions can cause problems like you describe as well. do you have any codes stored? if you can get a scanner that can look at your fuel trims and see what they are at, and if your scanner can see misfire counts, you can see which cylinder the misfires are occuring at. how long has it been acting this way? is it ONLY at idle that it has the problems? did you replace BOTH pre-cat O2 sensors? unfortunately its hard to diagnose problems like this, especially over the internet, but you've started at the right place by doing a tune up.

    1996 C1500 ECSB 5.7L AKA the "LS31", distributorless w/LS2 coils, RHS Heads, ZZ4 Cam, T56 6 speed, 12200411 PCM, 4.88s...Coming soon: forged twin turbo 383..

  4. #4
    Registered User 91chevyon22s's Avatar
    Join Date
    May 2008
    Location
    calgary, AB
    Posts
    26

    Re: 97 tahoe runs rich/misfires

    Well i figure its running rich because they exhaust smells very strongly like gas at an idle and when it fires up theres a bit of black smoke at first. i have plugged it in and it comes up as (random ignition misfire) The guy that put in the plugs put in ACdelco platinums, i heard the rapid fires were much better. and yes both O2's were replaced, even the after cat one was done. im thinking maybe its just ****ty plugs?
    Thanks!
    1997 2wd Tahoe,loaded,tinted,dropped,22's
    1995 2wd Suburban,tinted,2 12's, exhaust,roll pan, 7" touch screen
    1981 Short box,dropped 4/6, 468/th400, black on black
    1977 blazer 8" lift 454/4speed/205
    sittin on 38.5" swampers

  5. #5
    Registered User 91chevyon22s's Avatar
    Join Date
    May 2008
    Location
    calgary, AB
    Posts
    26

    Re: 97 tahoe runs rich/misfires

    Bump..has anyone had this problem,or know of anypossible solutions?
    1997 2wd Tahoe,loaded,tinted,dropped,22's
    1995 2wd Suburban,tinted,2 12's, exhaust,roll pan, 7" touch screen
    1981 Short box,dropped 4/6, 468/th400, black on black
    1977 blazer 8" lift 454/4speed/205
    sittin on 38.5" swampers

  6. #6
    S/C Z71
    Guest

    Re: 97 tahoe runs rich/misfires

    Do you still have the stock poppets and FPR in there?

  7. #7
    Registered User 91chevyon22s's Avatar
    Join Date
    May 2008
    Location
    calgary, AB
    Posts
    26

    Re: 97 tahoe runs rich/misfires

    To tell you the truth i have no idea i only got the truck a month ago, where are the poppets?
    1997 2wd Tahoe,loaded,tinted,dropped,22's
    1995 2wd Suburban,tinted,2 12's, exhaust,roll pan, 7" touch screen
    1981 Short box,dropped 4/6, 468/th400, black on black
    1977 blazer 8" lift 454/4speed/205
    sittin on 38.5" swampers

  8. #8
    S/C Z71
    Guest

    Re: 97 tahoe runs rich/misfires

    The poppets are the fuel injectors and they're in the intake manifold. It sounds like one or more of them are leaking or the FPR is leaking causing a rich condition upon start up.

  9. #9
    Registered User 91chevyon22s's Avatar
    Join Date
    May 2008
    Location
    calgary, AB
    Posts
    26

    Re: 97 tahoe runs rich/misfires

    so in order to get to the injectors i have to take off the intake?
    1997 2wd Tahoe,loaded,tinted,dropped,22's
    1995 2wd Suburban,tinted,2 12's, exhaust,roll pan, 7" touch screen
    1981 Short box,dropped 4/6, 468/th400, black on black
    1977 blazer 8" lift 454/4speed/205
    sittin on 38.5" swampers

  10. #10
    0_o o_0 0_o o_0 98GreenMachine's Avatar
    Join Date
    Aug 2005
    Location
    St. Paul, MN
    Age
    30
    Posts
    5,583

    Re: 97 tahoe runs rich/misfires

    You just have to remove the top half of the intake. There is a plastic shell that covers the fuel injectors and the fuel pressure regulator. Once this piece is off, it will look like this:

    08 HHR LS - 2.2 | 5 speed | 30 MPG

    98 K1500 Z71 - 204k | L31 | 60E | 3.73's | 3" BL | 33x12.5x15 Dick Cepek F-C II's | Dynomax Ultra Flo X DI/DO | 14 MPG

    84 S15 Jimmy 2dr 4x4 - engine/tranny all rebuilt

  11. #11
    Registered User 91chevyon22s's Avatar
    Join Date
    May 2008
    Location
    calgary, AB
    Posts
    26

    Re: 97 tahoe runs rich/misfires

    ahh awesome thanks for the picture!!
    so the dist. tb. all that stuff comes off with the plastic cover yes? and i dont have to get any gaskets for this do i?

    sorry im new to vortecs lol used to play with TBI's a lot
    Last edited by 91chevyon22s; 01-22-2009 at 11:07 AM.
    1997 2wd Tahoe,loaded,tinted,dropped,22's
    1995 2wd Suburban,tinted,2 12's, exhaust,roll pan, 7" touch screen
    1981 Short box,dropped 4/6, 468/th400, black on black
    1977 blazer 8" lift 454/4speed/205
    sittin on 38.5" swampers

  12. #12
    Registered User 91chevyon22s's Avatar
    Join Date
    May 2008
    Location
    calgary, AB
    Posts
    26

    Re: 97 tahoe runs rich/misfires

    okay i pulled out all the plugst see whats up, they all seem a little to carboned up and black for like 1 month old and the back 4 are nasty black an grungy and smell of gas... FPR??
    Last edited by 91chevyon22s; 01-22-2009 at 01:24 PM.
    1997 2wd Tahoe,loaded,tinted,dropped,22's
    1995 2wd Suburban,tinted,2 12's, exhaust,roll pan, 7" touch screen
    1981 Short box,dropped 4/6, 468/th400, black on black
    1977 blazer 8" lift 454/4speed/205
    sittin on 38.5" swampers

  13. #13
    Hired Goon Aloicious's Avatar
    Join Date
    Mar 2007
    Location
    UT
    Age
    33
    Posts
    1,996

    Re: 97 tahoe runs rich/misfires

    Quote Originally Posted by 91chevyon22s
    okay i pulled out all the plugst see whats up, they all seem a little to carboned up and black for like 1 month old and the back 4 are nasty black an grungy and smell of gas... FPR??
    yeah if you're getting P0300, it smells rich and you're running the original poppets, theres a good possibility its either the poppets themselves or the FPR leaking causing the problem, either one will require pulling the upper intake.
    you shouldn't need to pull the dizzy for just the upper intake, but the TB and what not will have to come off, the upper intake is the black plastic dome looking part that the TB mounts on, then there is an aluminum lower intake below that.
    Last edited by Aloicious; 01-22-2009 at 02:26 PM.

    1996 C1500 ECSB 5.7L AKA the "LS31", distributorless w/LS2 coils, RHS Heads, ZZ4 Cam, T56 6 speed, 12200411 PCM, 4.88s...Coming soon: forged twin turbo 383..

  14. #14
    Registered User 91chevyon22s's Avatar
    Join Date
    May 2008
    Location
    calgary, AB
    Posts
    26

    Re: 97 tahoe runs rich/misfires

    And how do i go about checking the poppets and FPR?
    Is there a way to test them to see if they are leaking?
    Last edited by 91chevyon22s; 01-22-2009 at 02:31 PM.
    1997 2wd Tahoe,loaded,tinted,dropped,22's
    1995 2wd Suburban,tinted,2 12's, exhaust,roll pan, 7" touch screen
    1981 Short box,dropped 4/6, 468/th400, black on black
    1977 blazer 8" lift 454/4speed/205
    sittin on 38.5" swampers

  15. #15
    Hired Goon Aloicious's Avatar
    Join Date
    Mar 2007
    Location
    UT
    Age
    33
    Posts
    1,996

    Re: 97 tahoe runs rich/misfires

    Quote Originally Posted by 91chevyon22s
    And how do i go about checking the poppets and FPR?
    Is there a way to test them to see if they are leaking?
    I'm not running a regular manifold and never had issues like this with it when I was running it, so I can't help much, someone like 98greenmachine who has done a lot with them would be able to help out more.

    1996 C1500 ECSB 5.7L AKA the "LS31", distributorless w/LS2 coils, RHS Heads, ZZ4 Cam, T56 6 speed, 12200411 PCM, 4.88s...Coming soon: forged twin turbo 383..

  16. #16
    S/C Z71
    Guest

    Re: 97 tahoe runs rich/misfires

    If you're going to take the upper intake off then just replace the injector spider (all 8 injectors and the FPR) with the updated unit. You shouldn't have to remove the distributor.
    Last edited by S/C Z71; 01-22-2009 at 03:41 PM.

  17. #17
    Registered User 91chevyon22s's Avatar
    Join Date
    May 2008
    Location
    calgary, AB
    Posts
    26

    Re: 97 tahoe runs rich/misfires

    well i pulled out all the plugs cleaned em up a bit cause they were pretty black looking i took out the IAC and cleaned it up a little bit put it back togther went for a ride and the missing is still there but not nearly as bad...i think the ac delco platinums are the problem... lol might go with rapid fires see if that will solve it??
    1997 2wd Tahoe,loaded,tinted,dropped,22's
    1995 2wd Suburban,tinted,2 12's, exhaust,roll pan, 7" touch screen
    1981 Short box,dropped 4/6, 468/th400, black on black
    1977 blazer 8" lift 454/4speed/205
    sittin on 38.5" swampers

  18. #18
    Registered User 91chevyon22s's Avatar
    Join Date
    May 2008
    Location
    calgary, AB
    Posts
    26

    Re: 97 tahoe runs rich/misfires

    any ideas??
    1997 2wd Tahoe,loaded,tinted,dropped,22's
    1995 2wd Suburban,tinted,2 12's, exhaust,roll pan, 7" touch screen
    1981 Short box,dropped 4/6, 468/th400, black on black
    1977 blazer 8" lift 454/4speed/205
    sittin on 38.5" swampers

  19. #19
    S/C Z71
    Guest

    Re: 97 tahoe runs rich/misfires

    Ever change the fuel filter? What's the pressure?

  20. #20
    Registered User 91chevyon22s's Avatar
    Join Date
    May 2008
    Location
    calgary, AB
    Posts
    26

    Re: 97 tahoe runs rich/misfires

    Brand new fuel filter. have not checked the pressure yet..
    1997 2wd Tahoe,loaded,tinted,dropped,22's
    1995 2wd Suburban,tinted,2 12's, exhaust,roll pan, 7" touch screen
    1981 Short box,dropped 4/6, 468/th400, black on black
    1977 blazer 8" lift 454/4speed/205
    sittin on 38.5" swampers

 

 

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •