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  1. #1

    Unhappy Newbie to forum...Need 96 Tahoe help

    My new to me 96 Tahoe 5.7 vortec is having serious running issues. Runs rough, backfires (popping sound) coming from the exhaust, the exhaust smells heavily of fuel and is white and thick. Oil smells like fuel.

    Sometimes it will idle normally and sound fine, no weird noises, but if you give it any fuel it will start popping and running rough again. And don't even think about turning on the a/c, the vehicle immediatly cuts off as soon as the compressor tries to kick in. The exhaust and cat is new. Fuel pressure regulator is new.

    Cleaned the maf and the egr. New plugs and wires. I realize there are several things that could be wrong or a combination of things but I am hoping someone can give me some good ideas or a starting point as I don't want to chase this problem. This vehicle sat for 6 months before the problems started so we added a can of seafoam and some fresh gas thinking it may have some bad gas but no change.

    Help if possible please, thanks.

  2. #2
    Sr. Engineer nickgiacalone's Avatar
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    welcome to the site! im sure someone will have some insight on your problem
    -Nick
    2013 Silverado 1500 4x4 LT, Z71 Appearance Package, Vortec 5.3L AFM
    Victory Red, Ebony Cloth
    Custom pin striping, Bed Rail Protectors, GM Bed Liner, Husky Liner Floor Liners, Tint, Wade In-Channel Window Visors, Tractor Supply Black Low Profile Toolbox


  3. #3
    Legend

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    Well the white smoke can be the result of the seafoam, but it can also mean the headgaskets are shot. White smoke in my experiance has always been headgaskets, those 5.7 vortecs are notorious for the intake gaskets going bad too.
    99 K1500 Suburban LT "THE BEAST"
    Hypertech III, K&N, true dual
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  4. #4

    Default

    Probably the first set of things I would do:

    1) Hook up a scanner and pull codes and check sensor outputs to see if ther is anything out of whack.

    2) Check fuel pressure to make sure fuel is getting adequate fuel

    3) Check for spark leak from the wires. When you changed the plugs, was there anything in their condition that might indicate a problem (deposits or anything like that)?
    '98 K1500 Suburban LS 5.7 L 4L60E NV246 ARB
    '92 Ford Explorer XLT 4x4 4.0 L A4LD BW13-54 Trac-loc rear
    "My toys were the greasy cogs and springs and pistons that lay around all over the place, and these, I can promise you, were far more fun to play with than most of the plastic rubbish children are given nowadays." Danny in Roald Dahl's Danny The Champion of the World

  5. #5

    Default Tahoe problems

    Quote Originally Posted by MrShorty View Post
    Probably the first set of things I would do:

    1) Hook up a scanner and pull codes and check sensor outputs to see if ther is anything out of whack.

    2) Check fuel pressure to make sure fuel is getting adequate fuel

    3) Check for spark leak from the wires. When you changed the plugs, was there anything in their condition that might indicate a problem (deposits or anything like that)?

    Scanner pulls no current codes, nothing previous either. I was thinking with the strong gas smell that it must be getting enough fuel but have not checked the pressure yet. And the spark plugs were done by the previous owner in the hopes that it would run better. I went back behind him and checked to make sure he had correctly put the wires back on and straightened out a rats nest of plug wires at the same time. I was hoping that was going to help and it seemed like it did a little bit because now it will start and idle on its own, which it wouldn't do before. I got this vehicle at a really good price just because they tried a bunch of things and couldn't figure out what was wrong with it. They took it to a shop who supposedly had it fixed, they did something with the fuel pressure regulator and supposedly set the timing. The previous owner said it ran pretty good until he cut it off at the gas station, he stated that when he started it back up that it was running crappy and burned up quite a bit of fuel getting it home which was only a couple miles. I thought maybe he might have gotten some bad gas (hoping anyway) and that some seafoam would help out, but that was not the case either.

  6. #6

    Default

    I think I solved the fuel smoke dilemma. changed the injector spider (which was totally trashed, very black and gunked up, collapsed lines and holes everywhere), intake gasket (which was blown out of the channel in the intake on one side), thermostat, oil and filter and she is running pretty good. Had me worried for a bit because she was still smoking when we first started her back up, but in a little while that cleared and now there is no smoke and hopefully will stay that way.

  7. #7

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    Great Job!! and thanks for the update.
    Gary

    99 K 1500 Suburban
    78 Silverado Big 10 w/factory 454
    00 S-10 Blazer
    1976 Trans Am
    1980 Honda CB900 Custom

  8. #8
    Master Mechanic Dr_Zero's Avatar
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    Quote Originally Posted by chipmunk222 View Post
    I think I solved the fuel smoke dilemma. changed the injector spider (which was totally trashed, very black and gunked up, collapsed lines and holes everywhere), intake gasket (which was blown out of the channel in the intake on one side), thermostat, oil and filter and she is running pretty good. Had me worried for a bit because she was still smoking when we first started her back up, but in a little while that cleared and now there is no smoke and hopefully will stay that way.


    Rock on! thanks for the update!
    My trucks!

    1996 GMC Suburban SLT
    1997 GMC Yukon SLT

  9. #9

    Default Short lived transformation.....

    Ok, well the tahoe ran great after changing the fuel spider, drove it around quite a bit Friday night and Saturday, but now it started acting up again.

    We stopped for gas last night with it running fine, upon starting it back up it ran really rough and didn't seem to want to idle which is the same complaint that the previous owner had said something about after getting gas, but after getting out of the parking lot it cleared up and ran fine all the way home.

    Started it up this morning and it ran fine again while sitting idling in the driveway but as soon as we started down the road it had a noticable miss, so we turned around and headed back to the house, cut it off in the driveway and let it sit for a couple minutes and started it back up, ...upon starting, it was running worse than before and started backfiring again, this time backfiring louder than it was before changing the fuel spider.

    Since it was raining and I hadn't changed the rotor or cap yet, I decided I would try that and it did provide a bit of relief, now it's not backfiring and seems to idle fine but it is missing as soon as you pull out to head down the road.

    ( It's starting to remind me of a barn sour horse that acts fine as long as it's at the barn or heading back to the barn, but gives you a fit otherwise.)

    I went out and got a fuel pressure tester to see if that will give some insight, anybody have any ideas?

  10. #10

    Default Help still needed if possible...

    The tahoe still has a miss and it's irritating that I can't figure it out. This is what has been done so far...

    Fuel spider, fuel pressure regulator, fuel pump ( that is running only 52 pound of pressure, just like the one that was taken out)

    Upper intake gasket

    Another set of new platinum plugs and new wires

    Cap, rotor

    Different MAF sensor, not new but looked a whole lot better, just wanted to see if it made a difference.

    Thought I may be mistaking a miss for a transmission shift problem so it
    now has a new filter and fluid in the trans. The old fluid and filter looked
    good and clean.

    Nothing has made a bit of difference, the vehicle is still doing the exact same thing, missing intermittantly and will sometimes run terribly rough when started but if you cut it off and restart the motor it will run fine.

    There is no check engine light, and has no stored codes. Is there something else I should check???

    Any help would be greatly appreciated as this problem is driving me crazy.

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