buck_hunter Posted November 28, 2011 Share Posted November 28, 2011 Well i got a few problems here on my 87 pioneer with the 4.0. First off my brake pedal has almost no pressure, i put a new brake line in because it had a leak, once that was installed i put new brake pads on the front, but i pratically have to push my pedal all the way to the floor before it comes to a stop. I'm thinking it might be the brake booster but i have no clue any help would be great! Next problem/question, it has had a rough idle since i bought it. I replaced the plugs, wires, rotor, distributor cap also cleaned out the throttle body with a little throttle body cleaner. She still seems to idle a little on the rough side I'm not sure if it would be a vaccuum leak maybe the O2 sensor, or if i have a faulty throttle positioning sensor or what. i really don't know where to go from this point any help would be great. Link to comment Share on other sites More sharing options...
tazer15 Posted November 28, 2011 Share Posted November 28, 2011 Id go ahead and replace the TPS they are know probs anyway so you know its new.As for the brakes id say do a WJ or XJ MC and booster swap in sounds like one of those is your prob anyway and you get an upgrade while your at it.Theres a big writeup in the DIY section. I'm in the middle of one now I found mine used off a WJ being parted out online for $80 and its been tested. Link to comment Share on other sites More sharing options...
RyanL Posted November 28, 2011 Share Posted November 28, 2011 When you replaced the brake line were you sure to flush all the air bubbles out of the lines with a pressure bleeder? If there are air pockets in the system it can cause the pedal to be spongy and brake response slow and light. If not, you grab a buddy and loosen the spigots on the drums and front brakes while he presses the pedal until no air bubbles show in the fluid coming out, then tighten it back up again. Repeat the process with all four spots until the desired tightness is achieved and you're good. It will tighten the pedal and improve braking response. Link to comment Share on other sites More sharing options...
cruiser54 Posted November 28, 2011 Share Posted November 28, 2011 Get a can of throttle body cleaner and spray where the intake manifold meets the head , throttle body bolts to the intake manifold, and around all the vacuum lines. When you spray on a vacuum leak, you'll know it. I have a write-up on TPS adjustment and testing, C101 connector cleaning, and another on ground refreshing if you want them. The ground refreshing needs to be done as does the C101 refreshing at least once in a Renix MJ's or XJ's lifetime. The grounding system and connectors in the harness on these Jeeps caused many issues that were blamed on faulty sensors that are costly to replace. Link to comment Share on other sites More sharing options...
carnuck Posted December 8, 2011 Share Posted December 8, 2011 The secondary brake line to the rear probably has air in it. Link to comment Share on other sites More sharing options...
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