GM Inside - Ford Inside - Ford Ranger - Jeep - American Muscle

Support FSC and see no ads! - Click Here
Page 1 of 2 12 LastLast
Results 1 to 20 of 24

TBI 350 Very Low Idle RPM

This is a discussion on TBI 350 Very Low Idle RPM within the Technical / Maintenance forums, part of the General Discussion category; My 1992 Sierra is idling at 200 RPM yes that says two hundred. I searched and found this thread and ...

  1. #1
    Formerly Redneck Rebel Dale Gribble's Avatar
    Join Date
    Dec 2006
    Location
    Lima, OH
    Age
    32
    Posts
    1,963

    TBI 350 Very Low Idle RPM


    Support FSC and see no ads! - Click Here
    My 1992 Sierra is idling at 200 RPM yes that says two hundred. I searched and found this thread and it appears that the general consensus is that a 350 should idle between 600 and 800 RPM. What could be causing the low idle speed?

    I would also assume that this is the reason my battery isn't recharging when I let my truck idle.
    "The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government"
    ~ Thomas Jefferson

  2. #2
    Random Words repomaster's Avatar
    Join Date
    Nov 2007
    Location
    Cypress, TX
    Age
    33
    Posts
    46

    Re: TBI 350 Very Low Idle RPM

    I don't have an answer for you but i'm sure curious to find out what some of the guru's have to say.

    On second thought it could be your fuel pressure.
    95 GMC C1500 Sierra SLT ECSB - L05 - 4L60E - 3.73

    Hold my beer and watch this $hit!

  3. #3
    Registered Woman Pleaser Kick's Avatar
    Join Date
    Mar 2006
    Location
    Lakefield, MN/Brookings, SD
    Posts
    1,802

    Re: TBI 350 Very Low Idle RPM

    this happends to me every once and awhile, also very low voltage.
    2013 2500HD Silverado.
    2000 Chevrolet 1500, Ranchhand, 285's, 16x8 soft 8's, in dash DVD, 600w JL 10".
    1994 Cadillac STS, 18" MB wheels, eibach pro kit springs, billet grille.(SOLD 8/27/11)
    1992 BMW 325i (SOLD 8/24/12)

  4. #4
    Formerly Redneck Rebel Dale Gribble's Avatar
    Join Date
    Dec 2006
    Location
    Lima, OH
    Age
    32
    Posts
    1,963

    Re: TBI 350 Very Low Idle RPM

    Quote Originally Posted by KickAss89chev
    this happends to me every once and awhile, also very low voltage.
    My voltage reads about 13.5 but my RPM's sit right on 200 RPM when left to idle.
    "The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government"
    ~ Thomas Jefferson

  5. #5
    GMC RULZZ NEUMANNZZ's Avatar
    Join Date
    Mar 2005
    Location
    San Diego
    Age
    47
    Posts
    20,226

    Re: TBI 350 Very Low Idle RPM

    maybe you have a stuck iac valve or clogged passage leading to it. ensure your grounds/wires are good to and from the battery.
    Ensure battery is fully charged and load tested.

    remove iac and clean passage ways and valve. dont push in on pintle. to check operation of iac valve while removed and wires connected, ignition on/ engine off, valve should cycle.


    Also ensure your tps sensor has a smooth linear response. with engine off ignition on, voltage should read .5-5.0 vdc(closed throttle to open throttle). use scan tool hooked to diagnostic port or multimeter with needleprobe on dark blue wire going to tps sensor.
    O2 GMC RCSB 4.8L V8 AUTO 3.73's
    rebuilt/beefed up 4L60E(at 43,000miles)
    Matching Ninja 500r


  6. #6
    Formerly Redneck Rebel Dale Gribble's Avatar
    Join Date
    Dec 2006
    Location
    Lima, OH
    Age
    32
    Posts
    1,963

    Re: TBI 350 Very Low Idle RPM

    Quote Originally Posted by NEUMANNZZ
    maybe you have a stuck iac valve or clogged passage leading to it. ensure your grounds/wires are good to and from the battery.
    Ensure battery is fully charged and load tested.

    remove iac and clean passage ways and valve. dont push in on pintle. to check operation of iac valve while removed and wires connected, ignition on/ engine off, valve should cycle.


    Also ensure your tps sensor has a smooth linear response. with engine off ignition on, voltage should read .5-5.0 vdc(closed throttle to open throttle). use scan tool hooked to diagnostic port or multimeter with needleprobe on dark blue wire going to tps sensor.
    Ok now what is an IAC Valve and where is it located? TPS is throttle positioning sensor right?
    "The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government"
    ~ Thomas Jefferson

  7. #7
    Registered Woman Pleaser Kick's Avatar
    Join Date
    Mar 2006
    Location
    Lakefield, MN/Brookings, SD
    Posts
    1,802

    Re: TBI 350 Very Low Idle RPM

    my idle will be real low, volts will read around 10-11, nothing bad, but if i turn on the ac, lights and radio the volts will go way down, and sometimes kill the truck. this doesnt happen all the time either, works normal quite a bit of the time.
    2013 2500HD Silverado.
    2000 Chevrolet 1500, Ranchhand, 285's, 16x8 soft 8's, in dash DVD, 600w JL 10".
    1994 Cadillac STS, 18" MB wheels, eibach pro kit springs, billet grille.(SOLD 8/27/11)
    1992 BMW 325i (SOLD 8/24/12)

  8. #8
    GMC RULZZ NEUMANNZZ's Avatar
    Join Date
    Mar 2005
    Location
    San Diego
    Age
    47
    Posts
    20,226

    Re: TBI 350 Very Low Idle RPM

    the throttle position sensor(tps) is on the passenger side of the thottle body(opposite side of the thottle lever)
    just behind it is the iac valve it screws in like a spark plug or is held in by two bolts. should be a two wire connector that you disconnect prior to removal.
    Last edited by NEUMANNZZ; 06-10-2008 at 08:15 PM.
    O2 GMC RCSB 4.8L V8 AUTO 3.73's
    rebuilt/beefed up 4L60E(at 43,000miles)
    Matching Ninja 500r


  9. #9
    Formerly Redneck Rebel Dale Gribble's Avatar
    Join Date
    Dec 2006
    Location
    Lima, OH
    Age
    32
    Posts
    1,963

    Re: TBI 350 Very Low Idle RPM

    Quote Originally Posted by NEUMANNZZ
    the throttle position sensor(tps) is on the passenger side of the thottle body(opposite side of the thottle lever)
    just behind it is the iac valve it screws in like a spark plug or is held in by two bolts. should be a two wire connector that you disconnect prior to removal.
    Thanks for the assistance Neumann I'll check those things out when I have some day light tommorow.
    "The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government"
    ~ Thomas Jefferson

  10. #10
    hucking fates this server FordeatinZ71's Avatar
    Join Date
    Aug 2002
    Location
    Slapoutoftown, AL
    Age
    31
    Posts
    7,302

    Re: TBI 350 Very Low Idle RPM

    well, your alternator isn't spinning fast enough at that low idle to put out the required amount of charge. your IAC is most likely the culprit, but if not, you could always just adjust the base idle screw. that's not the correct answer, but it would fix the issue...its on the side of the TB, just look at your throttle linkage...

    2004 GMC Sierra SLE Z71 rcsb, 5.3/4L60E/3.73/G80 time bomb...3" lift, tinted 03+ Silverado tails, plasti-dipped 16" wheels (unknown brand), 285/75/16 Thunderer M/T Extremes, Thrush Welded muffler...

  11. #11
    BHB
    BHB is offline
    More trucks than sense... BHB's Avatar
    Join Date
    Oct 2007
    Location
    New York
    Posts
    8,297

    Re: TBI 350 Very Low Idle RPM

    Heard somewhere it could be EGR related

    Quote Originally Posted by Big Angry
    Hey ****face, (yes I am violating the rules and flaming you, whaah)

  12. #12
    Registered User
    Join Date
    Jun 2008
    Location
    Martinsville, OH
    Age
    36
    Posts
    4

    Re: TBI 350 Very Low Idle RPM

    I have the same problem. It just happened all of a sudden one day, and now idles low after warm all the time. I have changed everything under the hood except for the knock sensor and the fuel pump. I think the knock sensor will make it run like that. It is running just like the timing is retarded. Have you found anything out with yours yet?

  13. #13
    Formerly Redneck Rebel Dale Gribble's Avatar
    Join Date
    Dec 2006
    Location
    Lima, OH
    Age
    32
    Posts
    1,963

    Re: TBI 350 Very Low Idle RPM

    Quote Originally Posted by JSchu
    I have the same problem. It just happened all of a sudden one day, and now idles low after warm all the time. I have changed everything under the hood except for the knock sensor and the fuel pump. I think the knock sensor will make it run like that. It is running just like the timing is retarded. Have you found anything out with yours yet?
    Nothing as of yet, I think I am just gonna leave it be for now since it doesn't really seem to affect anything other than my alternators ability to keep up at idle.
    "The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government"
    ~ Thomas Jefferson

  14. #14
    Registered User
    Join Date
    Feb 2004
    Location
    texas
    Posts
    582

    Re: TBI 350 Very Low Idle RPM

    I had strange problems with my '89 TBI suburban and tested and replaced multiple sensors because when i disconnected some of them, things got better. But in the end, it was my fuel pump.

    My point is that the computer can do strange things once a sensor is disconnected and you can maybe use this to your advantage to diagnose your problem.

    I'd say disconnect your sensors on top of the engine one at a time (and reconnect) and see if the idle goes up. That could rule out things like fuel pressure, etc.

    Just my opinion. I'm interested in what others think about that approach.

  15. #15
    Formerly Redneck Rebel Dale Gribble's Avatar
    Join Date
    Dec 2006
    Location
    Lima, OH
    Age
    32
    Posts
    1,963

    Re: TBI 350 Very Low Idle RPM

    Quote Originally Posted by aggiedave98
    I had strange problems with my '89 TBI suburban and tested and replaced multiple sensors because when i disconnected some of them, things got better. But in the end, it was my fuel pump.

    My point is that the computer can do strange things once a sensor is disconnected and you can maybe use this to your advantage to diagnose your problem.

    I'd say disconnect your sensors on top of the engine one at a time (and reconnect) and see if the idle goes up. That could rule out things like fuel pressure, etc.

    Just my opinion. I'm interested in what others think about that approach.
    It goes up when I disconnect the plug thats right behind the thermostat housing
    "The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government"
    ~ Thomas Jefferson

  16. #16
    hucking fates this server FordeatinZ71's Avatar
    Join Date
    Aug 2002
    Location
    Slapoutoftown, AL
    Age
    31
    Posts
    7,302

    Re: TBI 350 Very Low Idle RPM

    i bet i know what it is. that sounds like your coolant temp sensor. you have one for your computer, one for the gauge. most likely it's telling the motor it's cold all the time so it's compensating and making your idle low...

    2004 GMC Sierra SLE Z71 rcsb, 5.3/4L60E/3.73/G80 time bomb...3" lift, tinted 03+ Silverado tails, plasti-dipped 16" wheels (unknown brand), 285/75/16 Thunderer M/T Extremes, Thrush Welded muffler...

  17. #17
    TIGERZ TIGERZ's Avatar
    Join Date
    Aug 2008
    Location
    Long Beach, CA
    Age
    28
    Posts
    583

    Re: TBI 350 Very Low Idle RPM

    any update? did you figure it out?

  18. #18
    Formerly Redneck Rebel Dale Gribble's Avatar
    Join Date
    Dec 2006
    Location
    Lima, OH
    Age
    32
    Posts
    1,963

    Re: TBI 350 Very Low Idle RPM

    Quote Originally Posted by TIGERZ
    any update? did you figure it out?
    yep I changed my oil after 22,000 miles and now it idles around 600 rpm.
    "The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government"
    ~ Thomas Jefferson

  19. #19
    Registered User
    Join Date
    Feb 2004
    Location
    texas
    Posts
    582

    Re: TBI 350 Very Low Idle RPM

    what made you change it at 22k??? :)

  20. #20
    JUGS Racing SuperStepside's Avatar
    Join Date
    Jun 2007
    Location
    Miami, FL
    Posts
    1,766

    Re: TBI 350 Very Low Idle RPM

    Thats just wrong.

    1995 350 "Tool Box Injection"
    Going 4/6 with 20" Billet Specialties

 

 
Page 1 of 2 12 LastLast

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
  •