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Hey all, i'm the proud new owner of this '89 MJ. It came with some issues as most older jeeps do. First order of business, clean the throttle body and iac. Trying to eliminate the vacuum leak, which is massive. Kicking out a loud whoosh when i step on the gas pedal, limiting my top speed to 35 mph. PO installed an electric fan to help with overheating, seems to work well, keeping temps at 220 F if i can trust the thermostat. So i'll be under the hood for a while this week. The forum articles on vacuum leaks are helpful. Also i'll be looking for a new flexplate, mine is cracked. Any advice/info on sourcing a new one will be appreciated!
I made a post about my vacuum leak awhile back and you guys helped me figure out what's actually going on. Now I'm actually trying to fix it lol. So I have an 89 with the 4L/4WD and without going into tons of backstory, I pulled my dash to fix a water leak like 2 years ago. Sometime after that, I noticed that when I have my AC/Heat/Vent/Anything on and I'm climbing up a hill, the AC switches to defrost until I release the gas. Then, it goes back to whichever mode the controls are set to. It will do this occasionally on level ground but it's much more pronounced in 3rd/4th up a hill. I inspected the Vacuum reservoir in the front bumper and it appears fine. I looked over the lines in the engine compartment, can't see anything there either. I thought maybe it was the stupid vacuum disconnect for the axel since it's so loosy-goosy but disconnecting that and plugging the lines made no difference. I removed the stereo and lower dash to inspect everything I can see hoping I won't have to take the rest of the dash off but I'm not seeing anything clearly broken or loose except some cracks on the AC Control unit itself: There is another screw on the right side of the unit that has a similar crack as well and just flexing the unit will spread the crack apart. But I don't know how vacuum is routed through there and if it's possible that this could be the source of a leak. I have a Chrysler Service Manual for the 1990 Jeeps. I don't think there's much change between 89 and 90's as far as this is concerned? But I went through all the modes on my truck and they matched up with this (except my control unit doesn't have "Max AC"): So that at least gives me some sense that I reconnected the lines correctly when I reinstalled the dash. It's entirely possible that there are cracks on the lines I missed - They are all original with 267k miles on them so I'm sure they could all be replaced. I'm trying to follow lines back and inspect logically but as you guys know, they're not all super easy to get to. Jess