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suburban from hell

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by olds350, Jan 7, 2003.

  1. olds350

    olds350 Guest

    OK, here's my sad, sad story. BTW, I was just told about your site, so I hope SOMEONE out there can help. I have a '91 suburban /forums/images/graemlins/burb.gif that had the stock 350 TBI motor replaced this past March from a specialty engine swap company. The truck is a 2 wheel drive, posi rear, automatic w/ overdrive rigged to tow. From day one after the swap, the truck did not run right. To keep this thread short, here's what the truck is currently doing....
    >Very rough idle from a cold start
    >poor gas mileage. dropped to 12 from 18 on the hiway
    >Once truck is at operating temp, w/ the truck in gear and foot on the brake, like at a stopsign, the engine RPM's will drop occasonally (from 700 to 400) and will occasionally cut off.
    >No power at higher RPM's (freeway driving)
    >The most bizzare issue happens when you have the brown/black distributor wire in place and a timing gun firing at the timing mark on the pulley. When you give it gas and rev the engine up to 3K RPM, the timing mark will advance and then immediately drop back down. The timing will not stay advanced for power.
    >The hydrocarbons read very high for a new motor, in the 125 to 140 PPM range. The guy at the inspection shop said for a new engine, it should be around 30-40. This states the engine is running fat.

    As far as the engine goes, the long block was replaced. Over the past 8 months, the following has been replaced....
    >knock sensor
    >O2 sensor
    >coolant sensor
    >main computer and PROM
    >PROM has been replaced w/ hypertech chip
    >plugs, wires and cap
    >TBI pressure regulator, seals and injectors
    >vaccum line running to MAPS sensor

    I'm at my wits end. I'm really close to having a great bon fire in the back yard w/ the suburban as the center piece. I like the truck and bought it tow my travel trailer, but I can't stand the way it drives and mileage is killing me.

    Any suggestions at all???? HELP!!!!!!!
  2. olds350

    olds350 Guest

    Forgot a few more items replaced on the suburban.....

    >new fuel filter and pump
    >all gas lines blown out
    >new muffler and cat

    Thanks again!!!!
  3. imiceman44

    imiceman44 1 ton status Premium Member

    Aug 5, 2002
    Likes Received:
    Sacramento, CA
    I really can't tell much from here, but did you check the lash on the valves, or maybe check the timing chain for correct instal?
    There is definitely something wrong mechanically for such a drastic decrease in power.
    I don't think it has to do with tuning.
    And by the way, if you look, you will find there is a section for 2wd in this forum, as well as a section specifically for subs.
    This is a 4x4 foru, but it's OK I like the SuBS even in 2wd forms /forums/images/graemlins/smile.gif
  4. BigBurban350

    BigBurban350 1/2 ton status

    Jun 9, 2002
    Likes Received:
    Does this specialty engine swap place know about this, maybe you should have taken it up with them. /forums/images/graemlins/burb.gif /forums/images/graemlins/usaflag.gif
  5. skelly1

    skelly1 1/2 ton status

    Sep 2, 2002
    Likes Received:
    San Diego, CA
    Is the base timing right? Make sure it is the right timing (4 degrees BTDC??? maybe 10) at idle with the brown wire disconnected at the firewall. Also, HC is misfire, CO is rich, NOX is ping. 140 HC is not high for fuel injection if engine not up to temp. Also, does it have air injection? That will help light off the probably 3 way cat you got under there. Also, was that a loaded test i.e. on dyno, at idle or ??? Also what RPM? Lastly, are the plug wires going 18436572? Maybe a cracked plug from the install. Has there been a compression test done since the install? Maybe a tight valve? Did they re-use the
    TBI to manifold gasket? Hook up a voltmeter to the O2 sensor after it's up to temp and see what it does. Is it even getting up to operating temp? Maybe they forgot a t-stat. I don't know if you replaced the distributor yet, but those can be fragile if the rotor is pryed off with a screwdriver.
  6. chevystepside

    chevystepside 1/2 ton status

    Sep 23, 2002
    Likes Received:
    leadville colo
    i would take it back to the install shop and use the warrantty to the fullest. i hope that there is a warranty otherwise your screwed. but it does sound like that it is a mechanical prob like possibly timing chain installed in the wrong spot. some timing chain kits come marked for straight up 0 deg -advanced -retarded. three marks on the crank gear.pretty easy to get it wrong.
  7. olds350

    olds350 Guest

    You know, you write these messages and you always leave out something. As to the engine swap place, he has about 3 weeks of follow up work invested in the truck trying to find the problem. I think it's hurting his professional pride because he can't figure out the what the problem is. Last but not least, this is the second motor in the truck. Both motors displayed cxactly the same symptoms, so I don't think it's the motor. I think it's something timing related but I can't figure it out. Hope this helps w/ suggestion.

    Thanks all!

    BTCRAWFORD Registered Member

    Nov 20, 2002
    Likes Received:
    Have you checked the electrical connections to the computer controllers? Make sure non of the little pins are bent.
    These newer vehicles with computers are a little finnicky when it comes to the electrical connections.
  9. 85HeartBurb

    85HeartBurb 1/2 ton status

    Jan 10, 2002
    Likes Received:
    Temecula, south
    the EGR valve on my bigblock cured similar probs as far as rough idle and hydrocarbons..... /forums/images/graemlins/k5.gif
  10. Blazer1970

    Blazer1970 1/2 ton status

    Feb 17, 2000
    Likes Received:
    Old Mission, MI
    There is a guy who had a similar issue on the Pirate board, and I have seen this elsewhere before also. Check the distributor for worn out shaft/bushings. Pull the cap and try to wobble the rotor. If there is excessive play there, that is likely your problem. Those HEIs used with TBI seem to wear out like that. Usually when a motor swap is done like yours, they just stab the old distributor back in there and fire it up. That makes for a lot of miles on the original distributor. The play screws up the cam position sensor, thus screwing with the computer's ability to control the timing.
  11. Suffergauge

    Suffergauge 1/2 ton status

    Aug 1, 2002
    Likes Received:
    Olympia, Wa.
    I am gonna say that I think either you have
    1. The dist 180 out or
    2. You have some plug wires crossed

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