new to GMC can anyone help?

Discussion in 'General Chevy & GM Tech Questions' started by k_lakey, Mar 11, 2009.

  1. k_lakey

    k_lakey New Member

    i just got a 1990 gmc stepside 4x4 with a 5.7 a 4' lift and 33's on it and when i drive it feels realy slugish... its got a magnaflow cat back... take off is really slow.. can anyone help?
  2. GaryL

    GaryL New Member


    Welcome to the site.

    Do you know what gears you have in it? It sounds like you may not have enough gearing for the size tires you are running.

    You might also check the timing, if it is off it could cause sluggishness.
  3. bry2500

    bry2500 New Member

    I would agree about the timing, 33's are not significantly over sized so IMO they are less of a factor here. Still if the gearing has been changed from stock before then they become more of an issue.
  4. retired2001

    retired2001 New Member

    Welcome to the site. You didn't mention, but considering the age of the truck you might want to check out the catalitic converters. They can cause a lot of issues when they go bad. Just a thought.
  5. Jimmiee

    Jimmiee New Member

    Make sure to have it scanned for codes. There may be a code stored in memory that can point to the power loss.
  6. k_lakey

    k_lakey New Member

    i dont know what gears are in it... i think stock
  7. k_lakey

    k_lakey New Member

    and the catalitic converters looks new
  8. ct9a

    ct9a New Member

    An easy way to check the cat is by temperature. I picked up a cheap laser thermometer at Harbor Freight when I thought mine was going out.
  9. k_lakey

    k_lakey New Member

    how would i do this?
  10. Jimmiee

    Jimmiee New Member

    Easiest way is to take it to Autozone. They will scan it for you for free.
  11. k_lakey

    k_lakey New Member

    thank you so much for all the info...
  12. trackbird

    trackbird New Member

    Above ideas are good. Also, do all of the regular maintenance stuff... plugs, wires, fuel filter, air filter. It was only good for 200 HP when new, so don't expect it to fly.
  13. k_lakey

    k_lakey New Member

    i never expect it to fly... but i would like it to do better then what its doing now.. feels like im towing or pulling something huge! i have 33's on it now but would like to go up to 35's ... maybe 37's was thinking about getting a tune-up kit and doing that. maybe a cold air intake and a tbi spacer....
  14. k_lakey

    k_lakey New Member

    just talked to a friend that has a 5.7 in his truck and he can roast the tires... and he has 35's and over 200.000 miles in his and it all stock!
  15. cascott325

    cascott325 New Member

    congrats on the purchase. do a search for seafoam on this forum, and try it out
  16. k_lakey

    k_lakey New Member

    really... you think it maybe that e-z? i have used seafoam b-4... it is some good stuff. that would be SO COOL!! if it was that... knowing my luck... NOT! lol
  17. 04sierracrewcab

    04sierracrewcab New Member

    welcome to the club!


    The lazer thermoters are REALLY COOL!! I have played with them in my engien's class at school.
  18. dwill3015

    dwill3015 New Member

    Put a throtlle body spacer on it as well as a Hyperchip performance chip and either turn the top to your stock aril cleaner upside down or get an aftertmarket one. I have an 87 K5 Blazer with a new GM crate motor, 4-inch lift and 35's. Stock gearing is 3.73's and it was sluggish untill I did those 3 in-expensive mods and it was like night and day difference with low-end performance.
  19. cascott325

    cascott325 New Member

    thats what i need... low end performance. it accels good until i hit 2000 rpm's, then it just comes alive. like it just snorted crack or something! lol i have a throttle body spacer, had it installed and everything, but the fan and the shroud were too close for my k&n tube, so i had to take it back off. solution to that problem, electric fan. losing the clutch fan will give me more power, electric fans can keep me cooler, and i will have room for the tb spacer. i also really want to put in a dif. cam. just dont know enough about them
  20. k_lakey

    k_lakey New Member

    i put the seafoam in it today and filled it up with gas... but now there something new.... when i was pulling out of my driveway to the left.. then tryed to turn to the right the wheel was a lil off then it popped and the wheel moved about 1 inch... but the tires did not move..... and the steering wheel is **** to one side. i can post a video if that would help?

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