chinky20 Posted December 5, 2017 Share Posted December 5, 2017 First off, Awesome site. I've learned a lot about my truck in the past few days. I would like some help as I get to understand these trucks. 1) How do I tell if my engine falls into the 'RENIX' category? I have a vacuum leak that I will be correcting. After reading some post on here, it was suggested to replace all of the lines as they are 30yrs. old. The part #'s were given ( Napa part number BK 715-1367,Napa part number BK-715-1366.,part number 715-1365.) by cruiser54 but I noticed it stated it was for the 'RENIX' model. I'm currently only blowing air through the defrost vents as no other vents will blow. I also have an irregular idle that sounds like your flooring it on start up. It will die down after 1-3 seconds, then idle between high and low whenever in park or neutral. Regardless of the temperature of the motor. If the truck is in gear it idles perfectly. Thoughts? I appreciate any help in advance. Looking forward to getting this little gem running like a top. Link to comment Share on other sites More sharing options...
Ωhm Posted December 5, 2017 Share Posted December 5, 2017 Your running RENIX. When your H/C ventilation system fails, the default is defrost vents only. Fix your vacuum leaks, then see how it idles. Link to comment Share on other sites More sharing options...
chinky20 Posted December 6, 2017 Author Share Posted December 6, 2017 Ωhm, thanks for the quick reply. I will be ordering the suggested vacuum lines tonight. As for the H/C ventilation system failing. Needless to say, I'm not a mechanic in any kind of way. But I don't mind trying. What would you suggest my next steps on this being? Thanks again for the help. Link to comment Share on other sites More sharing options...
Ωhm Posted December 6, 2017 Share Posted December 6, 2017 Not sure if I can help on the HVAC. You got a vacuum leak somewhere. Start a new topic: H/C ventilation, defrost only. I'll assume all other HVAC works. Link to comment Share on other sites More sharing options...
Eagle Posted December 6, 2017 Share Posted December 6, 2017 1 hour ago, chinky20 said: Ωhm, thanks for the quick reply. I will be ordering the suggested vacuum lines tonight. As for the H/C ventilation system failing. Needless to say, I'm not a mechanic in any kind of way. But I don't mind trying. What would you suggest my next steps on this being? Thanks again for the help. Maybe some additional explanation will help. The location of the heat or A/C air outlets is controlled by vacuum-actuated flappers. The dash control doesn't move the doors directly, it controls a vacuum switch that then controls where the flappers are set by using engine vacuum to move the flappers. When there's a vacuum leak, the default position is to direct air up through the defrost outlets. The usual failure that causes this is the line from the vacuum resrvoir behind the front bumper, and it often fails where the vacuum line runs under the battery tray. But any significant vacuum leak can create the same problem so, since you're looking at busted vacuum lines, before you waste any time trying to diagnose the air flow issue, fix all the vacuum lines you can find and that very well may cure your problem. Link to comment Share on other sites More sharing options...
carnuck Posted December 6, 2017 Share Posted December 6, 2017 Go above your gas pedal and see if the vacuum hose is off there. Then, if your front bumper on passenger’s side is damaged, the vacuum ball may be crunched. (I move mine up under the hood) The vacuum comes from the intake behind the throttle body and crosses to the passenger’s side. There is a Y by the coolant fill bottle and heater valve. One was capped unless you have cruise control or AC. My Comanches:2nd Louey 1987 SB Sporttruck2.5L/AX-4 2wd (for now) 3.55 D35 205/75R/15 with studs and new windshield and headliner. First Louey 1988 SB Sporttruck 4.0L/BA10/5 2wd (for now) 3.07 D35 235/75R/15 on steel wheels 90 MJ LB parts rig. 107K miles rustbucket from the belt 4.0/Auto with matching front axle for 2Lt. Link to comment Share on other sites More sharing options...
mass.casualty Posted December 6, 2017 Share Posted December 6, 2017 Check your EGR valve as well. I just picked up a 89 MJ and, like you, i studied everything cruiser54 offered. Found my EGR was faulty and the cause of my massive vacuum leaked. All my lines were good and i was scratching my head until i found cruiser’s write ups. Then promptly printed them and added them to the FSM i found onlineSent from my iPhone using Tapatalk Link to comment Share on other sites More sharing options...
chinky20 Posted December 6, 2017 Author Share Posted December 6, 2017 Thanks for all of the replies. After tracing the lines as instructed above I found this hose that easily came free. My best guess is it connects to the hose coming out of the firewall? Link to comment Share on other sites More sharing options...
chinky20 Posted December 6, 2017 Author Share Posted December 6, 2017 Tried to get picture of the area I’m talking about but says I can’t upload anymore. Quick question. Replacing all three sets of lines as suggested by cruiser would include all of these correct? Link to comment Share on other sites More sharing options...
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