Results 1 to 19 of 19

idling and rpm problem

This is a discussion on idling and rpm problem within the General Help forums, part of the LSx Technical Help Section category; Just recently my ls1 started idling differently with the rpms fluctuating up and down. Everything was fine last time I ...

  1. #1
    Junior Member Hogsters's Avatar
    Join Date
    Dec 2015
    Location
    California
    Posts
    8

    Blk/Blu
    1998 TJ

    idling and rpm problem

    Just recently my ls1 started idling differently with the rpms fluctuating up and down. Everything was fine last time I had started it so Im not sure what happened. I've replaced the plugs and the inline fuel filter... there was no change after replacing either one. At some point it just dies out, but I can easily start it back up. Anybody have an idea what might be going on? I not to familiar with these motors and it sits im my 98 Tj. Came out of a 1998 Firebird.

  2. #2
    Smiles for 9.5 Years cammed goat's Avatar
    Join Date
    Jan 2009
    Location
    Paterson/Ridgewood, NJ
    Posts
    11,474

    Phantom Black Metallic
    2004 GTO M6

    Could be a number of things. A vacuum leak could be the culprit. I would start by checking the intake tube between the airbox and throttle body as that could be loose/cracked, check your idle air control valve(IAC) as those become dirty over time. Also check and clean your mass airflow sensor between the airbox and intake tube as they become dirty. Clean that with some CRC MAF cleaner. Could also be an EGR issue as those tend to crack over time. If you need anything else, give a shout.


    extreme dimensions, driveshaft shop, harrop, hid(35watt/6k) lows, hurst, k&n, led fogs, maverick man, mishimoto, nitto, revshift, slp, stern st-1, smoked sidemarkers, whiteline poly radius rod bushings

  3. #3
    Moderator 35th-ANV-SS's Avatar
    Join Date
    Oct 2008
    Location
    Wherever life takes me
    Posts
    12,465

    Red
    02 35th LE Camaro SS

    Any codes?
    It's on jackstands.

  4. #4
    Junior Member Hogsters's Avatar
    Join Date
    Dec 2015
    Location
    California
    Posts
    8

    Blk/Blu
    1998 TJ

    Thanks for the feedback! I'll be trying these one by one and step by step along with a few youtube video's on "how to". Hopefully I can find a diagram to show me the location of the parts somewhere online.
    I tried running my OBD11 but not able to bring up any codes, I'm guessing because it was an engine swap to the jeep tj, I really don't know.
    I'll post back with results hopefully this week.
    Last edited by Hogsters; 12-06-2015 at 05:11 PM. Reason: improper sentenence

  5. #5
    Moderator 35th-ANV-SS's Avatar
    Join Date
    Oct 2008
    Location
    Wherever life takes me
    Posts
    12,465

    Red
    02 35th LE Camaro SS

    I am just going to guess a vacuum leak somewhere...like a hole or crack in one of the vacuum lines. That's the #1 cause of rev's jumping around. Cammed goat's recommendations are also good ones. Let us know what you find.

  6. #6
    Junior Member Hogsters's Avatar
    Join Date
    Dec 2015
    Location
    California
    Posts
    8

    Blk/Blu
    1998 TJ

    Quote Originally Posted by 35th-ANV-SS View Post
    I am just going to guess a vacuum leak somewhere...like a hole or crack in one of the vacuum lines. That's the #1 cause of rev's jumping around. Cammed goat's recommendations are also good ones. Let us know what you find.
    I'll start there seems to be the cheapest solution, and I can hear air hissing under the hood but im not sure if it's good air I'm hearing, sounds like the back side of the block on passenger side against the firewell.
    I will keep updated as I move along till problem is solved.

  7. #7
    Spaz is My Mentor SMWS6TA's Avatar
    Join Date
    Feb 2009
    Location
    Ugy Lower Corner of AL
    Posts
    10,509

    Navy Blue Metallic
    98 T/A w/a little mods...

    There are a couple of things it could be.

    If you still have it in stock configuration the EGR tube that comes from the drivers side valve cover (rear) around to the same location on the passenger valve cover then runs along the passenger side of the intake that connects to the pcv. This setup almost always causes vacuum leaks.

    2nd cause back there could be the MAP sensor is crack, loose. Also since this is a engine swap into another vehicle I would look at the intake as well if you don't find an obvious leak.



    When you can post up some pics. Interested in seeing a TJ with a LS1 in it.

  8. #8
    Junior Member Hogsters's Avatar
    Join Date
    Dec 2015
    Location
    California
    Posts
    8

    Blk/Blu
    1998 TJ

    Ok I took the throttle body off today and cleaned it up. Unscrewed the two little connectors on it and spayed some of that cleaner on them, (Im not sure what they call the connectors). I checked for cracks but couldn't find any.... it still not right. I thought Id take it to the shop but Its going to be a while before I can do that. Should I take a picture of the engine tomorrow and post it here. With the new infor for the EGR I might be able to do more, and I don't know what the IAC looks like. Is it possible that cleaning them wont work but a new one will? Looks like most of the parts mentioned here are all around $25-$35.... I can afford to do that now but cant afford the labor a shop is going to charge me.

    - - - Updated - - -

    Quote Originally Posted by SMWS6TA View Post
    There are a couple of things it could be.

    If you still have it in stock configuration the EGR tube that comes from the drivers side valve cover (rear) around to the same location on the passenger valve cover then runs along the passenger side of the intake that connects to the pcv. This setup almost always causes vacuum leaks.

    2nd cause back there could be the MAP sensor is crack, loose. Also since this is a engine swap into another vehicle I would look at the intake as well if you don't find an obvious leak.



    When you can post up some pics. Interested in seeing a TJ with a LS1 in it.

    Ok Will Do, and thanks for the feedback!

  9. #9
    Smiles for 9.5 Years cammed goat's Avatar
    Join Date
    Jan 2009
    Location
    Paterson/Ridgewood, NJ
    Posts
    11,474

    Phantom Black Metallic
    2004 GTO M6

    The IAC is located on the driver side of the throttle body and is held in with two torx-head screws. It is chrome with a black plastic connector. Once you unplug/remove the IAC, check for build up of soot on the pintle and inspect the hole where it goes into the throttle body as the soot cakes up in there too. Use throttle body cleaner and a rag for both and get back to us with what you find.

  10. #10
    Junior Member Hogsters's Avatar
    Join Date
    Dec 2015
    Location
    California
    Posts
    8

    Blk/Blu
    1998 TJ

    Boy was I wrong about the part prices. So I replaced the MAF with no results. I've ordered the IAC and will put the results up on Friday after I receive it.




    [IMG][/IMG]

    [IMG][/IMG]

    [IMG][/IMG]

    [IMG][/IMG]

    [IMG][/IMG]

    [IMG][/IMG]
    Last edited by Hogsters; 12-08-2015 at 04:24 PM. Reason: Forgot to add progress

  11. #11
    Moderator 35th-ANV-SS's Avatar
    Join Date
    Oct 2008
    Location
    Wherever life takes me
    Posts
    12,465

    Red
    02 35th LE Camaro SS

    Nice looking jeep. I would try to diagnose it more before just wasting money by throwing parts at it. That will get expensive quickly and might not result in any improvement.

  12. #12
    Junior Member Hogsters's Avatar
    Join Date
    Dec 2015
    Location
    California
    Posts
    8

    Blk/Blu
    1998 TJ

    Well I at a loss....my IAC part came in today, I installed with no results....actually rpms were higher. Don't know what next, but I cant keep replacing parts at their prices.

  13. #13
    Member RONS98TA's Avatar
    Join Date
    Jan 2009
    Location
    MARYLAND
    Age
    44
    Posts
    803

    BLACK
    1998 PONTIAC TA

    You can take some carburetor cleaner and spray it along all your vacuum lines while the engine is running. If you spray across a leaking/cracked hose, the idle will go down. That is the cheapest and easiest way to eliminate all the vacuum hoses for leaks. Trying to fix a problem by just buying stuff, is NOT the way to find your problem. When spraying said carb cleaner, be careful not to spray to much cleaner on some of the plastic connectors. So try to avoid spraying any plastic. Just keep a rag handy and wipe it off asap. Some plastic is extremely sensitive to the carb spray and will get eaten up by it. The plastic will look like you took a lighter to it.
    1998 Pontiac TA, stock heads, FAST 90, FAST 90 TB, FLP LT, off road y-pipe with cat delete, flow master muffler, comp cams 54-457-11 223/231-610/617-112 LSA, Pro charger D1SC with FMIC @ 8psi, FROST tune, VIG 3200 stall, built 4l60e, snow meth kit, MOSER 12 bolt 373 gears, Derale 13900 trans cooler.

  14. #14
    Junior Member Hogsters's Avatar
    Join Date
    Dec 2015
    Location
    California
    Posts
    8

    Blk/Blu
    1998 TJ

    Ok so one last go around today and I find a little valve thingy that looks like it should have a hose connected to it but I cant find one, so I think maybe just maybe it suppose to have a rubber cap on it. (It's located on the back of the block in between firewall) So I find a rubber cap put it on and Wala! it runs great again!!! thanks to all those that chimed in, I 61 years old and still learning
    What is the name of that thing anyways, what is it called and do?

    [IMG][/IMG]


  15. #15
    Spaz is My Mentor SMWS6TA's Avatar
    Join Date
    Feb 2009
    Location
    Ugy Lower Corner of AL
    Posts
    10,509

    Navy Blue Metallic
    98 T/A w/a little mods...

    idling and rpm problem

    yeah you need that. It's suppose to go to your brake booster or at least on a f body.

    Not sure how yours is setup.
    http://www.ls1.com/forums/f7/my-6-liter-build-174257/

    http://www.ls1.com/forums/f8/my-8-8-rear-build-165553/

    6.0L Block - Forged 403 built, breaking it in , Polluter Stg3 Cam, FAST 102mm Intake, NW102 TB, MSD wires, NGK TR6 plugs, Truck Coil Packs, LS3 Fuel Injectors, CC Pacesetter LT Headers, TS&P ORY, QTP e-Cutout, Magnaflow Muffler, 104mm Air Lid & Line Lock, Catch Can, Stage 2 T56 w/Viper shaft, PRO 5.0 Shifter, Tick MC, Monster Stg 4 Clutch, QT SFI BH, MWC DSL, UMI: SFC, PHB, LCA's, LCA Relocation Brackets & TA, Hotchkis Springs (1" Drop), YR1 Snowflake Wheels wrapped in NT555 tires & Custom Fab Ford 8.8 rear w/4.10 Yukon Gears, WSQ Hood, 3"CM Strange Eng Drive Shaft.

    Horsepower never lies, but is often lied about!

  16. #16
    Member RONS98TA's Avatar
    Join Date
    Jan 2009
    Location
    MARYLAND
    Age
    44
    Posts
    803

    BLACK
    1998 PONTIAC TA

    That is your map sensor. (Manifold Absolute Pressure) The part # is on it. (16212460) On an F-body LS1, is it located on the back of the intake manifold, next to the firewall as you have explained. It should be plugged into the manifold with the tab that you have capped off with the rubber plug. It is possible that whoever did your install just bypassed that, or it came lose from your intake. I know on an f-body, that lil booger is a PITA to get to. If it is unplugged though, as you have found out, it will cause a major vacuum leak and make the engine run like crap. Awesome looking build by the way. That looks bada$$.

  17. #17
    Member RONS98TA's Avatar
    Join Date
    Jan 2009
    Location
    MARYLAND
    Age
    44
    Posts
    803

    BLACK
    1998 PONTIAC TA

    Correction. I now realize you probably referring to the black plastic stem that the MAP sensor is connected to. Yes, as SMWS6TA stated, that stem usually has a rubber hose that goes over to the brake booster, to provide power brake assist. If you look at your brake master cylinder, there is a round black case that should have a hose coming off of it, that is IF you have power brakes.

  18. #18
    Junior Member Hogsters's Avatar
    Join Date
    Dec 2015
    Location
    California
    Posts
    8

    Blk/Blu
    1998 TJ

    So much knowledge here! I'm assuming since I have hydraulic steering and a brake booster as well, is the reason I'm not using the vacuum hose, and that's why it's capped off. Thanks for all the help with trouble shooting and detailed explanations. Thank You!!

  19. #19
    Smiles for 9.5 Years cammed goat's Avatar
    Join Date
    Jan 2009
    Location
    Paterson/Ridgewood, NJ
    Posts
    11,474

    Phantom Black Metallic
    2004 GTO M6

    Glad to see you fixed the issue.

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Idling
    By edrvsqz1980 in forum Firebird / WS6
    Replies: 27
    Last Post: 07-22-2010, 03:15 AM
  2. A kill while idling?
    By IH8EVRY1 in forum Kill Stories
    Replies: 18
    Last Post: 05-11-2010, 05:19 AM
  3. Idling RPM's?
    By qwk01ta in forum General Help
    Replies: 3
    Last Post: 04-27-2010, 11:09 PM
  4. problem idling
    By grouch0jr in forum General Help
    Replies: 14
    Last Post: 12-18-2009, 08:04 AM
  5. Idling at 650 to 750 RPM's
    By 9t8z28 in forum External Engine
    Replies: 4
    Last Post: 10-31-2006, 07:25 AM

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
  •