88 k1500 5.7-should have so much more

Discussion in 'GM Powertrain' started by JohnnyC, Jul 20, 2010.

  1. JohnnyC

    JohnnyC New Member

    wondering (hoping) if someone can point me in right direction...
    truck runs REALLY boggy at low rpms, but if you get on the gas it screams pretty good above 3,000 rpm +/-. therefore, normal driving is downright boggy. i had same engine in another truck, which wasn't taken care of like this one, and it ran awesome.

    timing is set to zero (got rid of pinging)
    new plugs, wires, cap, rotor
    had a lot of carbon buildup, threw egr codes, cleared it up with seafoam & manual cleaning of egr valve.

    just seems like there is a sensor, or vacuum problem i am missing. cant find it! PLEASE HELP?!
  2. wolven0862

    wolven0862 New Member

    TBI or Carb If TBI i had same problum and it was the eletronic sensers on the TBI system I have a 89 Jimmy. Also used to have a 85 and with that one the carb jetts would plug up a little.Hope this maybe helps you
  3. JohnnyC

    JohnnyC New Member

    its TBI. what sensors u talking about? wouldn't they throw a OBD I code? thanks!!!
  4. wolven0862

    wolven0862 New Member

    when you take the breather off, the ones right on the top they are the ones that control the in put of the fuel
  5. L0sts0ul

    L0sts0ul New Member

    those are the injectors. Did you check the fuel filter? or replace it? check fuel pressure through the RPM range? check compression?
  6. murdog94

    murdog94 New Member

    Have you done a TPS sweep test? Also you may want to check out the Idle air control valve (IAC), since that can cause the motor to bog down low.. I would clean it out and go from there... Have you checked the pickup coil on the dist? Also have you checked out the temp sensor (there are a few threads on the site here on the Temp sensor, and the IAC, and a sweep test)
    I have a 1988 With the same motor and was having a very similar problem Well actually it was boggy the entire time. The distributor was shot in mine.
  7. JohnnyC

    JohnnyC New Member

    boggy 5.7 unless you punch throttle

    AWESOME, thanks guys! ill have to look up that IAC, and sweep test. i am planning on doing a fuel pressure test this week, filter is really old. is 13 p.s.i. the typical pressure thru rpm range?
    might be the distributor, we'll have to see. im not giving up on it. what are symptoms of bad distr?
  8. murdog94

    murdog94 New Member

    What you listed basically are the symtoms of a bad dist, the pick up coil on mine was completely shot and not allowing for any advance in timing.. However i would start with a fuel filter.. and yes 13PSI is all these pumps put out. A good pump is actually anything over 12psi...
  9. JohnnyC

    JohnnyC New Member

    thanks murdog,
    im not liking the looks of my fuel line fittings. doing the filter is gonna suck. i guess ill test the pressure first, may have to buy a tester.
  10. murdog94

    murdog94 New Member

    My lines looked pretty bad and they actually came really easy, just spray the fittings down with PB blaster for a few days before you attempt it and it will be good to go..
  11. JohnnyC

    JohnnyC New Member

    yup, been sprayin em for a few days now.
    hey, you ever see a purple & pink wire at the back of the block by the distributor? its just hangin there and doesn't look like it's been hooked up to anything...ever. i checked all over the place and there isn't anything not hooked up. its on a 6" length of harness, so youd think id be able to find where it might go. my buddy said it might be for some option my truck didnt come with???
  12. murdog94

    murdog94 New Member

    I am thinking it might be something that someone ran. because i only have a purple wire back there other than the ones that have a place and that is for my 4wd...
  13. JohnnyC

    JohnnyC New Member

    88 5.7 wants to run great but somethings up, maybe its this pink & purple wire?

    its definitely a factory line&plug. any other ideas out there?? on a good tip, i replaced the regulator diaphram in the TB this weekend. no different. also, got ticked off & reamed out the cat converter. gained some pep but now got a code 32 again. why? anybody got any ideas on this? i was told OBD I systems can run without a cat and not get any codes! guess i was lied to. also, someone told me that aftermarket egr valves (not OEM) are junk? can anyone shed some light on any of this?
    thanks guys

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