88 silverado questions.

Discussion in 'GM Powertrain' started by coolkittens, Mar 4, 2011.

  1. coolkittens

    coolkittens New Member

    I have a couple silverados with a couple different questions.
    first. i have a 1994 z71. it has lost almost all power. and ive exhausted all options i can think of. all new sensors ecm injectors. fuel filter. pump. vacuum lines. everything. the only thing left in my mind could be the cat. the truck has a 5.7 with i believe all the smog pump stuff removed. not too sure of the history but i got it with 150k on it. it now has about 350k. i think it might be clogged because the guy who had it said he never replaced it. and i never have. so maybe that might be the problem. also once it gets hot i hear a dull roar from right where it is under the cab. so im thinking it backed up so much it found another route out.

    onto my 1988 silverado which i just purchased about 15 minutes prior to this post. i paid 700 for it so its not too bad. its got a six cylinder in it. which i dont know the size. on the drive home. i noticed a bad tap in the motor. which was not there at the beginning. not a big problem i pressume. probably a lifter loose. or a valve tap. not sure. but i hope its nothing major. truck has alot of power for the motor. so im sure its not extreme. im just wondering if its common for that motor for the studs to walk out because i had a previous truck where the studs backed out on me. couple more questions but nothing major. it has a leak at the collector. im guessing blown gasket. but like i said it has enough power for me not to be super worried. just wondering what the tap could be. with putting my ear close i can hear its coming from the top of the motor somewhere.
    the crank and everything feel tight. and it doesnt have any dead pistons. everythings firing.

    thank you.
    sorry for the run ons.
  2. I have had the same problem that you are experiencing with the 94 and it was due to the cats being clogged. The PO flat out told me that he had continued to use leaded gas because it was cheaper (this was a few years ago) and it clogged the cats. No power, no acceleration eventually sitting on the side of the road with the engine running but not enough power to actually move the rig. Sort of like those old teen movies where they would stick a banana in the tail pipe. I replaced the cats and everything was golden. For the 88 I would X2 Caddiac because I have had great success in knocking out lifter knock with Seafoam (did you see what I did there LOL). Anyway let us know what you did and what the result was.
  3. silveradotrailblazer

    silveradotrailblazer Epic Member 5+ Years ROTM Winner 5000 Posts

    Welcome to the club. On the '94 I'm sure its the cat since its original and has about 350K on it.
  4. stephan

    stephan Rockstar 4 Years 5000 Posts

    X2 on the cat on the '94, but you can check it first by having a helper rev the snot outta it while you put your hand over the tailpipe. You should feel a good deal of air flow. If not, then it is probably plugged.
    On the "88 I would do an oil change first. It probably needs it unless it is extremely clean already. I always get 1 or 2 lifters clicking when mine is getting close to needing an oil change
  5. a.graham52

    a.graham52 Rockstar 100 Posts

    on the 94 remove the o2 sensors and that will releave pressure if the cats are plugged nad you will get your power back. that will tel you if its the cats. on your 88 i think you should run some seafoam in the oil for bout 10 minutes, change the oil and filter (always good when you first get a veicle that way YOU KNOW its been done) and put good oil in it.
  6. silveradotrailblazer

    silveradotrailblazer Epic Member 5+ Years ROTM Winner 5000 Posts

    MarvelMistry oil additive is good for cleaning sticky/dirty lifters.
  7. coolkittens

    coolkittens New Member

    ive heard alot of talk about this sea fome stuff. never used it. can i get it at advanced. and how does the application happen. and whats needed.
    im mechanically inclined. just never heard of it. and thanks for replys.
  8. giorge

    giorge Rockstar 100 Posts

    I haven't heard of it either but here is their website. http://www.seafoamsales.com/ That might give you some more info about it. I have had an exhaust leak before that I thought was a lifter. But I would check the converters first (on both) and change the oil on the 88 and if you still have the tick check your exhaust manifold for leaks, the Marvel Mystery Oil is a good idea also (great stuff).

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