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need help vacuum diagram - 4.2 1988

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  • need help vacuum diagram - 4.2 1988

    Can anyone either email me a diagram/ or point me to a site where I can copy a vacuum diagram for a 1988 YJ with 4.2?? Any info. greatly appreciated!
    I have a Jeep (sort of, its stock, high mileage 95YJ) Sporty sold, mower blew up, all money went for new mower and still have payments. Life!

  • #2
    Good Luck, all your going to get is a website showing a diagram that makes very little sense. Im going thru the same thing. I have an 89 YJ that I just finished the Nutter Bypass on and now Im trying to get the carb and vacuum lines all hooked up again. This thing was a real piece of work when I bought it. Then your going to find out that the stock 258 Carter carb is a piece of #*$&. Its like one thing after another. I dont know about you, but I wish someone would publish a manual,,,,,step 1, step 2, kinda like a flow chart, if it looks like this, go to B, if it looks like this go to step C, if not, go to D etc, etc, Not all engines are alike or have the same crap missing. Its alot of fun playing with though so hang in there and dont give up.


    • #3
      Oh by the way,,,,lets not even get into emissions!!!!!!!Happy Holidays, 75+ degrees in Arizona today, boy if that dosent say Ho Ho Ho, I dont know what does....


      • #4
        Here is the website. Before I converted to the Howell TBI, this site is the best site to help you unwind the vacuum hoses. No one ever said the vacuum/emission system on the 4.2 liter was simple. The Chilton manual has a good trouble shooting guide, too(taken from the shop manual).

        There are some subtle differences (errors?) when comparing the diagram on this site to my shop manuals, but I finally convinced myself the diagram here was correct.

        It took me a couple of hours when I did it on my 1990, but when it was done, it all worked great. I had to replace a couple of the vacuum switches on the firewall but when you have it hooked up right it actually does work.

        That said, a fuel injection conversion is the way to go. You get to take all the vacuum lines, switches, etc. and throw them out except for the canister/fuel tank lines and of course the EGR lines. Howell, Holley,, MOPAR, all are great options. I went with the Howell system and then I custom tuned a chip and it all works great.
        David Ingebretsen, M.S., M.E.<br />Collision Forensics & Engineering, Inc.<br />