***Login to the Forum here ***

Support FSC and see no ads! - Click Here
Page 1 of 4 123 ... LastLast
Results 1 to 20 of 61

87 Chevy TBI 350 Idling issues

This is a discussion on 87 Chevy TBI 350 Idling issues within the Classics forums, part of the General Discussion category; I have an 87 Chevy with a 350 TBI motor that I have been trying to solve idling issues on ...

  1. #1
    Registered User
    Join Date
    Mar 2011
    Location
    Lexington, SC
    Posts
    70

    87 Chevy TBI 350 Idling issues


    Support FSC and see no ads! - Click Here
    I have an 87 Chevy with a 350 TBI motor that I have been trying to solve idling issues on for quite some time now. Can anyone who is pretty knowledgeable with this system help me or can someone tell me where I can go to get some good help. I don't even mind paying for a good technician. This truck has stumped three garages now and I'm almost at a dead end. Any help would be appreciated, thanks!

  2. #2
    Registered User jim_in_dorris's Avatar
    Join Date
    May 2007
    Location
    almost in oregon, but still california
    Posts
    791

    Re: 87 Chevy TBI 350 Idling issues

    Is it stock? Have you smoked it for vacuum leaks? What are the symptoms?

  3. #3
    You won't like my tastes Swims350's Avatar
    Join Date
    Dec 2009
    Location
    Logan WV
    Posts
    2,538

    Re: 87 Chevy TBI 350 Idling issues

    what exactly does it do? it can be egr causing bad idle. you can check it by pulling up on the inside of it whle the truck is running and if it changes the idle and makes it worse it should be working fine, if it didn't change the idle then it's stuck open and causing bad idle.

    Chris

    88 K1500 RCSB work in progress.

  4. #4
    Registered User
    Join Date
    Nov 2008
    Location
    Missouri
    Posts
    126

    Re: 87 Chevy TBI 350 Idling issues

    I've had a couple of them in the suburban setup. I am just taking a wild guess from my experience on this and check your ignition. I bet if you get under the cap on it you will find that you can go straigt upgrade or replace weights and you will be suprised at how much better it runs.

  5. #5
    Real 4x4s' Rust ryan_thompson87's Avatar
    Join Date
    May 2007
    Location
    Portage La Prairie, Manitoba, Canada
    Posts
    3,044

    Re: 87 Chevy TBI 350 Idling issues

    It's TBI. No mechanical advance.

    Check intake gaskets, TB, base gasket, check fuel pressure, the basics. Does it just idle poorly or is it missing?

    87 K30-355 Vortec TBI/TH350/208/Dana 60/14FF/4.56s/Detroit/37"Bogger/Ult.TBI Mods/XtremeFI FPR vac. reference/EP241 Pump/LS1 Fans

    07 GMC Sierra Classic - 2" Rough Country Full Leveling Kit/285 Duratracs/Gibson Exhaust/10% Tint/Billet Grille


  6. #6
    Registered User
    Join Date
    Mar 2011
    Location
    Lexington, SC
    Posts
    70

    Re: 87 Chevy TBI 350 Idling issues

    Sorry for the missing info guys but I wanted to make sure I was in the right place before I started spamming the wrong forum area.

    I bought this truck a couple months ago and the guy I bought it from said the only thing wrong with the truck was the tranny was bad (700R4). My biggest problem in life is that I tend to believe what look and seam to be good honest people. I did at least crank it up and listen to what sounded like a good mechanically sound engine other than the little surging it had until it warmed up. So I bought the truck and had the tranny overhauled. To make a long story short, over the course of the few weeks I've had this truck it has been real inconsistent on it's issues. One day/hour/min it will be surging. The next it will be totally crap and won't idle at all. The next could be high idling. The next could be a GREAT idle. I've had this truck run like brand new for a whole day and have left it that way when I hit the bed and next time I turn the key she will be right back to day 1. Most of the time when it's bad at idle it's bad upon accelerating but there have been few times that it could be bad at idle and great upon accelerating and never the other way around.

    I have changed: Plugs, wires, cap, rotor, ignition module, coil pickup, ignition coil, (3) computers, fuel filter, O2 sensor, coolant temp sensor, map sensor, idle air control valve, idle position sensor and throttle body gasket. I have checked the timing and replaced all the vacuum lines. Fuel pressure is good.

    The strange thing is.......when it's acting up I can unhook the coolant temp sensor and it runs perfect! I've tested the coolant temp and it tested fine. Besides, if it was bad I would have had to bought a defect which I know can happen. One of the 2 garages I took it to said I had a worn throttle shaft linkage and wanted to sale me a whole new tbi for $700+ and we could "START" there. I laughed and told them to tally up my bill ($200 for diagnostics!) and I would take it home and try and used one before I bought one but thanks. I just don't see how a worn throttle shaft could cause the inconsistent issues this truck has. Several people I have talk to agree and one even said he's never seen an old, fine running, tbi that didn't have any play in it's shaft.

    The last guy that worked on it, who is supposedly a wiz at these early model fuel injected trucks, told me he had no clue. The only thing he DID see was that the alternator was giving 16 volts and he didn't know if that could be screwing with my circuits or popping my ecms. Outside of the alt, what I'm left pondering over is bad fuel injectors, bad/wrong prom or cal pak. Someone has also told me I might wanna even check the dual tank switch as it could be going bad.

    Sorry for getting long winded but I wanted to be thorough as no one seems to know what's wrong with this truck. If anyone has any ideas please let me know. In the mean time I'm gonna go pull this alternator wire and if it hasn't already fried this ecm I'll eliminate that possibility. Thanks in advance!

  7. #7
    Registered User
    Join Date
    Mar 2011
    Location
    Lexington, SC
    Posts
    70

    Re: 87 Chevy TBI 350 Idling issues

    Quote Originally Posted by ryan_thompson87 View Post
    It's TBI. No mechanical advance.

    Check intake gaskets, TB, base gasket, check fuel pressure, the basics. Does it just idle poorly or is it missing?
    Ryan, it's not missing I don't think as I can watch the injector cones varying at bad idle.

  8. #8
    You won't like my tastes Swims350's Avatar
    Join Date
    Dec 2009
    Location
    Logan WV
    Posts
    2,538

    Re: 87 Chevy TBI 350 Idling issues

    if you unplug the temp sensor and it runs fine, change it. period it's cheap change it.

    you need to check fuel pressure it may be too weak and starving the motor and when you unplg the cts it runs richer and makes it better.

    Chris

    88 K1500 RCSB work in progress.

  9. #9
    Registered User
    Join Date
    Mar 2011
    Location
    Lexington, SC
    Posts
    70

    Re: 87 Chevy TBI 350 Idling issues

    Quote Originally Posted by Swims350 View Post
    if you unplug the temp sensor and it runs fine, change it. period it's cheap change it.

    you need to check fuel pressure it may be too weak and starving the motor and when you unplg the cts it runs richer and makes it better.
    I have changed: Plugs, wires, cap, rotor, ignition module, coil pickup, ignition coil, (3) computers, fuel filter, O2 sensor, coolant temp sensor, map sensor, idle air control valve, idle position sensor and throttle body gasket. I have checked the timing and replaced all the vacuum lines. Fuel pressure is good.
    I just went for another drive without the cts connected and on further note it's not actually running perfect as it appeared the other day. It definitely runs a lot better but still has it's slight surges and stumbles......noticeable under acceleration as well.
    Last edited by SKYDoutCHEVY; 06-10-2011 at 11:13 AM.

  10. #10
    Registered User
    Join Date
    Mar 2003
    Location
    Las Vegas
    Age
    34
    Posts
    141

    Re: 87 Chevy TBI 350 Idling issues

    I have a 91 with TBI, it was having some really bad idle issues a couple years ago. Like you, I did a full tune up, replaced about all the sensors with no results. I ended up disassembling the throttle body and cleaning it one night and ever since it's idled great. It had a lot of build up in it, one of the passages was almost all the way clogged. I got a gasket kit and a few cans of carb cleaner from auto zone. It's a pretty cheap thing to try, it can't hurt to clean it.

    91 RCSB, 5/7 drop, 4.3, 5 speed

  11. #11
    You won't like my tastes Swims350's Avatar
    Join Date
    Dec 2009
    Location
    Logan WV
    Posts
    2,538

    Re: 87 Chevy TBI 350 Idling issues

    oh yea all that stuff adds up, the IAC pasage can get clogged up and run bad, and to the best of my knowledge from reading and seeing pics there's little screens or filters behind the fuel lines in the tbi and maybe some on the injectors too that can get plugged up, but I would think either, except for the iac would show the injectors dripping or not spraying well.

    The egr can cause bad idle, not sure on surging and all, but a fuel pressure check is in order for sure, it could be a broke reg. spring in the tbi not having enough psi or maybe the pump is going down.

    Chris

    88 K1500 RCSB work in progress.

  12. #12
    Registered User
    Join Date
    Mar 2011
    Location
    Lexington, SC
    Posts
    70

    Re: 87 Chevy TBI 350 Idling issues

    Quote Originally Posted by Swims350 View Post
    oh yea all that stuff adds up, the IAC pasage can get clogged up and run bad, and to the best of my knowledge from reading and seeing pics there's little screens or filters behind the fuel lines in the tbi and maybe some on the injectors too that can get plugged up, but I would think either, except for the iac would show the injectors dripping or not spraying well.

    The egr can cause bad idle, not sure on surging and all, but a fuel pressure check is in order for sure, it could be a broke reg. spring in the tbi not having enough psi or maybe the pump is going down.
    Ok Swim, you got me seriously thinking about the IAC possibilities. For some reason I've never been able to discount something fishy about that IAC. I did install a new one but now, after reading your post, I'm starting to wonder about that IAC passage being blocked or just even something in that tbi acting up. 92 Z71 is now the third person who has told me they had the same problem and after either rebuilding or replacing the tbi their problems were gone. I was seriously contemplating giving up on this truck but I believe a tbi replacement is in order considering you can find them in junk yards all the time for so cheap. If it fixes or even alters my issues I'll probably go on ahead and purchase a totally remanufactured tbi complete with the injector assembly included.
    Last edited by SKYDoutCHEVY; 06-10-2011 at 10:14 PM.

  13. #13
    Real 4x4s' Rust ryan_thompson87's Avatar
    Join Date
    May 2007
    Location
    Portage La Prairie, Manitoba, Canada
    Posts
    3,044

    Re: 87 Chevy TBI 350 Idling issues

    What he said about the CTS is also right. When you unplug it, the ECM thinks it's -40 degrees and should start DUMPING fuel to it, in an effort to make it warm up faster. Mine won't even start with the CTS unplugged.

    87 K30-355 Vortec TBI/TH350/208/Dana 60/14FF/4.56s/Detroit/37"Bogger/Ult.TBI Mods/XtremeFI FPR vac. reference/EP241 Pump/LS1 Fans

    07 GMC Sierra Classic - 2" Rough Country Full Leveling Kit/285 Duratracs/Gibson Exhaust/10% Tint/Billet Grille


  14. #14
    "Just going for a drive" rich weyand's Avatar
    Join Date
    Apr 2010
    Location
    Bloomington, IN
    Age
    61
    Posts
    768

    Re: 87 Chevy TBI 350 Idling issues

    This is an oldie but a goodie, and it's simple:

    You did clean up your ground straps, right?

    If the frame, the cab, and the engine don't agree on what "0" volts is, all kinds of weird things happen, because none of the sensors will be read correctly. It will also be intermittent as hell depending on temp, humidity, etc.

    You should have a ground strap from the frame to the engine, probably on the drivers side from the front of the engine to the frame rail, and one on the passenger side from the head to the firewall. Take them off, clean off the mounting eyes, clean off the mating surfaces, and put them back on with new star washers.

    Rich
    1978 K-10 DD
    350 w/Comp 12-300-4, Edelbrock 1406+2601, Hooker headers, H-pipe duals,
    Flowmaster 40s, dual tanks w/dual gauges, heated leather buckets,
    JVC KD-AHD69 head unit, 4xKicker DS400, Lanzar VCTBS8 powered subwoofer

  15. #15
    You won't like my tastes Swims350's Avatar
    Join Date
    Dec 2009
    Location
    Logan WV
    Posts
    2,538

    Re: 87 Chevy TBI 350 Idling issues

    mine's the same way it will not start with the cts unhooked and when I plug it back in it takes a while to start and then puffs out fuel smoke when it does.

    Chris

    88 K1500 RCSB work in progress.

  16. #16
    You won't like my tastes Swims350's Avatar
    Join Date
    Dec 2009
    Location
    Logan WV
    Posts
    2,538

    Re: 87 Chevy TBI 350 Idling issues

    stinking spam BS

    Chris

    88 K1500 RCSB work in progress.

  17. #17
    GMC RULZZ NEUMANNZZ's Avatar
    Join Date
    Mar 2005
    Location
    San Diego
    Age
    47
    Posts
    20,558

    Re: 87 Chevy TBI 350 Idling issues

    whats fuel pressure reading? check fuel filter.
    Last edited by NEUMANNZZ; 06-12-2011 at 03:04 PM.
    O2 GMC RCSB 4.8L V8 AUTO 3.73's
    rebuilt/beefed up 4L60E(at 43,000miles)
    Matching Ninja 500r


  18. #18
    Registered User
    Join Date
    Mar 2011
    Location
    Lexington, SC
    Posts
    70

    Re: 87 Chevy TBI 350 Idling issues

    Sorry it's been a few days since I have updated and i appreciate everyone trying to help me out. For some reason, the site stopped notifying me by email that my thread was receiving responses.

    As far as the throttle body is concerned, I eliminated that by swapping the entire throttle body (including IAC valve and TPS) with my Uncle's out of his full size blazer with the same exact setup and have the same issues. It is still dumping fuel from the injectors.

    Rich, I checked and cleaned all the ground wires.

    Neumanzz, fuel pressure looks good (15psi) and filter was changed

    I replaced the prom with no luck.

    I was able to get it to throw some codes. I'm getting codes 42 and 43 so I started scanning the knock sensor circuit. PROBLEM! The knock sensor wire is missing! Could this wire that's missing be my problem??? My first assumption is that, with no wire, the ESC module definitely can't receive a signal from the knock sensor and therefor can't effect the timing. But obviously I'm know genius with these computer systems and I could be wrong. Could it cause an open circuit some how and still effect the timing? If I'm right, could the ESC module be bad?

    In the meantime I guess I'll try a salvage yard for a wire to try as I've heard the dealers are a little proud of them.
    Last edited by SKYDoutCHEVY; 06-21-2011 at 07:33 AM.

  19. #19
    Real 4x4s' Rust ryan_thompson87's Avatar
    Join Date
    May 2007
    Location
    Portage La Prairie, Manitoba, Canada
    Posts
    3,044

    Re: 87 Chevy TBI 350 Idling issues

    Mines currently unhooked (stick got jammed but there and tore the wire off) Been that way for awhile and it runs same as always. CEL doesn't even come on.

    87 K30-355 Vortec TBI/TH350/208/Dana 60/14FF/4.56s/Detroit/37"Bogger/Ult.TBI Mods/XtremeFI FPR vac. reference/EP241 Pump/LS1 Fans

    07 GMC Sierra Classic - 2" Rough Country Full Leveling Kit/285 Duratracs/Gibson Exhaust/10% Tint/Billet Grille


  20. #20
    Registered User para driver's Avatar
    Join Date
    May 2009
    Location
    Dallas
    Posts
    564

    Re: 87 Chevy TBI 350 Idling issues

    go through it and clean/check every connector under the hood.. yes it's a bunch of work, but it sounds like you have some 'floating' sensor or component issues.. the throttle body bushings to wear and leak a little air, but not enough in my experience to make an engine act like that. it sounds like you have some intermittent issues, and heat related.. so the only sensible action is to go through everything, one step at a time.. much cheaper than just throwing parts at it.
    '95 Tahoe LT 4x4, TBI with Vortec crate motor.
    God created all men, and Sam Colt made them equal.

 

 
Page 1 of 4 123 ... 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
  •