intake gaskets

Discussion in 'Chevy Suburban Forum (GMC Yukon XL)' started by mudpuppy, Feb 28, 2009.

  1. mudpuppy

    mudpuppy Rockstar 100 Posts

    i heard from someone that my engine(1994 350) has been known for bad intake gaskets. is it possible for the gaskets to go bad and still for the most part run fine, but at or near idle act like it has a vacuum leak? it does not have any leaks on the outside but yet acts like it has a vacuum leak.
  2. wigwag78

    wigwag78 New Member

    Not sure but if it is bad enough it could. Have you tried running a search on old threads yet.
  3. ct9a

    ct9a Epic Member 5+ Years 1000 Posts

    Ineresting... I've never heard this. Please keep us updated if you find anything more out. You have the TBI 5.7L, correct?
  4. mudpuppy

    mudpuppy Rockstar 100 Posts

    Yes its the 5.7 TBI. I checked the past threads and yes, it seems that the 4.3's and 5.7's(which mine is 5.7) have a very extensive history of intake gasket history. clearly the way the past threads describe it, im having the same problem. Surge at idle, loss of power and fuel millage, sometimes it will stall, and yes it has pop'd for o2 and maf sensors saying its running lean. Chevy has admitted it has problems with the intake gaskets for the 4.3 and 5.7 and all of what i have going on falls into what Chevy says it will do if the go out. Only took 3 years to find this info, but hey better late then never right? Just wish it would have been about $4k ago, at least now ill have a near new truck, i replaced all sensors and even rebuilt the TBI tring to fix this lol. Its to cold atm to do the intake gaskets, i need at least 50+ for the sealant to form rite so i have to wait till later this week to do it, just sure hope i can get it done before i leave for Afghan.
    Last edited: Feb 28, 2009
  5. mudpuppy

    mudpuppy Rockstar 100 Posts

    It got up over 50 today so i dug into the intake. Its all back together and the sealant is curing. When i popped the intake off there was a walnut sized oily resin ball at the port for the egr valve. There was enough there to clog it for sure. Im not certain yet but i think that might have been the surging idle problem. Ill be able to start it up and run it for a bit tomorrow. I hope the problem was fixed by doing this.
  6. Jimmiee

    Jimmiee Epic Member 5+ Years 1000 Posts

    Just for future reference if someone searches this subject If you suspect an intake leak on the inside the best way to test this is with a smoke machine. With the engine off introduce smoke into the crankcase. If you have an intake gasket leak smoke will find it's way up and out the carb or throttle body.
  7. mudpuppy

    mudpuppy Rockstar 100 Posts

    big improvement, it no longer slug at take off. has lots of power now that it didnt have before. sounds alot better, however its still surging at idle WTF.
  8. mudpuppy

    mudpuppy Rockstar 100 Posts

    wow long time ago for this post. just want to close it out with the solution. turned out the problem was wrong sized injectors so the a/f was way off. however it was a good thing to replace the injectors. due to the egr system there was alot of carbon build up in the intake to the point that air could no long pass. i suggest to any and all that have a few miles on there engine and still have the egr set up to consider changing the intake gaskets and cleaning out the intake while they have it off. this also makes for a great opportunity to change out your thermostat.
  9. silveradotrailblazer

    silveradotrailblazer Epic Member 5+ Years ROTM Winner 5000 Posts

    Thanks for that info mudpuppy. I'm sure it will help alot of people on this site.

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