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  1. #1
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    murdog94's Avatar
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    Default 1988 K2500 350TBI Power loss??

    Alright guys ive posted on this before I have a 1988 Chevrolet K2500 4X4, it is a 350 V-8 TBI, with a 5speed manual. 3.73gear ratio, extended cab long bed.. 265/70/17s. That is the full rundown on the truck.. Now here is my problem.. I start the truck up and it starts and runs great idles like its supposed to. I put her in first and take off. I hit the road about 100 yards from my house and hit it this this pulls like a mad mule... to 45mph which is the speed limit. I get down the road about 1/2 a mile and i dont have near as much power it still goes but just not great. There is no misfire, hesitation to really speak of.. I can drop a gear and floor it and wow there really isnt much there. I can go 72mph on the highway with the cruise on finally!! But it only goes like i know a 350 should for the first 1/2 mile.
    So here are the parts that i have replaced in the 3 months that i have owned it and been trying to figure out the problem. I have no CEL etc.. Oh and when i bought it there was less power than a 3cyl geo metro..


    The motor has 65K miles on it doesnt burn or leak a drop.. and the inital power tells me not a compression issue.
    I replaced the entire engine management harness, including under dash from a 1992...
    Fuel pump (last week and picked up 50% more power)
    fuel Filter (putting another one in since i did the fuel pump tomorrow)
    Plugs/wires/cap/rotor (looked like the had a million miles on them plugs ahd a clean burn)
    Airfilter (old one was dirty)
    TPS (original failed the seep test)
    Cleaned the entire throttle body
    Fuel Pressue regulator (helped with the power id say 10%)
    Coolant temp sensor (new 2 days ago)
    PCV valve checked.
    IAC cleaned and checked.
    EGR Cleaned, (thinking it might be a bit weak but i dont troubleguess)
    New starter (the old one went out nothing connected just adding this as well)
    Alternator is like new
    Coil is strong..
    Fuel lines are in good shape
    I have done a seafoam treatment to the fuel tank, and motor.
    No vacume (spelling??) leaks
    Checked injectors when the TBI was appart and checked spray looks all good to me.
    New 2 1/2 in straight pipe from the cat back.
    Engine was retimed, buy a local shop (my buddy had time i didnt)

    So here is what i am thinking it could be, PCM?? Not leaning that way thinkning something mechanical. EGR opening and being stuck open robbing top end power (i have good throttle till about 1/2 then the power goes up a bit but not as much as it should with more pedal). Ive done about everything else. Oh and i am wondering about the Disributor.. Could it be the Dist Pickup coil, or a related part??
    Otherwise i have changed it or ruled it out if it can be ruled out.

    So to give all of you the best picture on the power i am lossing and have gotten back here is the best description i have.
    When i bought the truck it wouldnt even spin the tires on dirt and had a heck of a time holding 70.
    Currently when it is being "sluggish" it will now spin the tires on dirt, and hold 70 on the interstate.
    When the power is where it is supposed to be it will lay rubber clean thru 1st and some of 2nd if i were to try. I live right off of a highway and it got me yesterday going to get the wife a coffee.. I was slightly surprised when i got on it and it went like............
    I know the power should be like that all the time. So please help me you all.
    Last edited by murdog94; 06-10-2010 at 04:52 AM.
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  2. #2

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    Does the truck use any coolant?
    When you hear hoofbeats, look for horses not zebras.

  3. #3

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    At this point I'd think you'd really want to get it on a scanner/logger and drive it, and see what's being read from the sensors and commanded by the ECM. From there you should be able to at least narrow down the problem.
    1986 Chevy G20 Tow Rig - 5.7 TBI conversion
    1978 Mustang II King Cobra Road Racer - Holley 650, MSD 6AL, 5 speed, 10 point Roll Cage, 9" posi, fuel cell, custom interior.

  4. #4
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    Default

    Quote Originally Posted by 2COR517 View Post
    Does the truck use any coolant?
    Nope not a drop.... I was thinking the same thing as you and everything is good to go..

    I did pull the cap and rotor today on a hunch.. The Pick-up-coil was covered in rust.. i cleaned it up and it actually made a bit of a difference. So im looking into that was well
    As for a scanner logger can the OBD1 even do that?? I know that the OBD2 is more than capable but i thought the OBD1 was just capable of some minor troubleshooting etc...
    Last edited by murdog94; 06-10-2010 at 10:27 PM.

  5. #5

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    GOOD scanners can read OBD1 live data. Look at the AutoXray 7000, for example. It's on my wish list.

    For a hundred bucks, I would replace the dist.

  6. #6
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    Default

    I was thinking the same thing. And i learn something new as well.. I cant remeber the name of the Snap-On scanner that is on my wish list. I have been considering replacing my Distributor, I sat around brainstorming at work tonight thinking about what the issues are. Since i have replaced basically everything else and cleaning the coil up did help. I just cant wrap my head around how the computer advances and retards the time with out actually moving anything. Because if the Distributor is hitting right however the rotor actually had more burn on the back side of the electrode than the front which isnt normal to me.

  7. #7
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    Default

    id go for the dist. ive had issues with the pick up coil in the distributor on several gm tbi motors and you can replace the pick up coil but it always ends up as a come back and have to replace the dist.
    IF IT AINT BROKE DONT FIX IT!
    GOD IS GREAT,BEER IS GOOD,AND PEOPLE ARE CRAZY

  8. #8
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    Default

    There is so much rust on the dist. i dont think i could get it appart enough to replace it anyhow.. its in rough shape to say the least..

  9. #9

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    Quote Originally Posted by murdog94 View Post
    There is so much rust on the dist. i dont think i could get it appart enough to replace it anyhow.. its in rough shape to say the least..
    That is an issue w/ the computer doing the timing, when I went to R & R my S-10 engine w/ the crate, I chouldn't get the dist to move. It was 9/11/01 and everyone was leaving early so I tried to get it out, in between phone calls from my wife asking me to come home, so I wrapped a chain around it and tried the shop forklift and ended up picking up the front of the truck!

    I wrapped around it w/ a bunch of rags and soaked it w/ CRC 5-56 ['bout 1/2 qt] and went home.

    Next day it came out by hand...All I did was replace the 'o' ring in it b/4 installing it in the crate.
    Still Loyal to GM after all these years...:shocked:
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    1988 S-10 small cab/longbed HT3.4L Crate Engine
    1970 Nova 250 I-6, factory 3 sp floor shifter.
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  10. #10
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    Default

    Quote Originally Posted by wis bang View Post
    That is an issue w/ the computer doing the timing, when I went to R & R my S-10 engine w/ the crate, I chouldn't get the dist to move. It was 9/11/01 and everyone was leaving early so I tried to get it out, in between phone calls from my wife asking me to come home, so I wrapped a chain around it and tried the shop forklift and ended up picking up the front of the truck!

    I wrapped around it w/ a bunch of rags and soaked it w/ CRC 5-56 ['bout 1/2 qt] and went home.

    Next day it came out by hand...All I did was replace the 'o' ring in it b/4 installing it in the crate.
    Oh no not rust there.. she moves freely.. The problem is the rust under the cap, and the pickup coil basically being covered as well.. It is just ugly, plus the rotor is looser than well___ thanks to the rust.. Ill take pics when i pull it appart and show you all how pretty this is and what happens when you buy something from someone who thinks that a little power loss isnt a big deal..

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