Dom U Posted April 9, 2015 Share Posted April 9, 2015 1988 4.0 auto 4wd. Pioneer Okay so you all know what's been done. Okay so late November last year I through a rod out the engine block 2 weeks after buying the truck. Got a junk yard engine with 115,xxx miles. Got it installed replaced CPS because we cut it somehow while pulling the old engine out. Put the JY engine in ran great had your normal 4.0 with a sticky lifter. Drove it daily untill about 2 weeks ago I over heated and cracked the cooliant tank (closed system). Replaced water pump, cooliant tank and most the clamps/hoses. Replace my cracked valve cover and gasket. Swap from idiot lights to gauge a 3/4 gauge cluster along with oil and temp switchs also replaced battery cables they were horrible looking. Air filter aswell Cool good to go... So I think. Well I drive it and its running like garbage. After a little searching found the line from throttle body to MAP sensor was broke in half. Due to it no longer being a purchable item I relaced it with a 3/16 steel brake line. Now I'm sure its good togo! Take a drive about 6 miles into the drive I feel a nice jolting back fire. Not a severe back fire just enough to feel it. As I'm coming to the stop sign truck dies. Starts right back up no problem at all. Get home can't find anything wrong. Iv done most of cruisers tips. Ground refreshing is all done. Upgraded ground from firewall to fuel rail bolt with a 4ga wire and more.. I keep driving it around to see how its acting will do goes for awhile then ill have the little backfire and dies when I use my brakes to stop. Iv relized it ONLY dies once I Start Useing my brakes. I also notice anytime I use my brakes every light gets dimmer,head lights, instrumental lights radio every light in the truck. Now before I start throwing money at unneeded parts what do you guys think could be the problem? Its my daily driver right now and I rely on it for work. Any help is appreciated. Link to comment Share on other sites More sharing options...
shelbyluvv Posted April 9, 2015 Share Posted April 9, 2015 Chaffed wires by the brake pedal, corrosion in the brake light switch, corrosion in the tail light sockets or bad ground behind the driver side tail light. Link to comment Share on other sites More sharing options...
Megadan Posted April 9, 2015 Share Posted April 9, 2015 Sounds like some random wiring gremlin, maybe a short. I know the wiring on my 88 pioneer is...to put it nicely...screwed. It could be unrelated, but that would be my guess. I haven't had your exact problem, so hopefully someone who has experienced something similar will chime in. Link to comment Share on other sites More sharing options...
Dom U Posted April 9, 2015 Author Share Posted April 9, 2015 Chaffed wires by the brake pedal, corrosion in the brake light switch, corrosion in the tail light sockets or bad ground behind the driver side tail light.Brake areas are very clean. The fuel pump switch behind the tail light has been cleaned uo etc. Link to comment Share on other sites More sharing options...
Dom U Posted April 9, 2015 Author Share Posted April 9, 2015 Sounds like some random wiring gremlin, maybe a short. I know the wiring on my 88 pioneer is...to put it nicely...screwed. It could be unrelated, but that would be my guess. I haven't had your exact problem, so hopefully someone who has experienced something similar will chime in.I was thinking somthing similar but I can't locate and messed up wires all the grounds have been refreshed and I can't figure out if a short would even cause a slight backfire? Link to comment Share on other sites More sharing options...
Megadan Posted April 9, 2015 Share Posted April 9, 2015 Many of my problems are located at the fuse box or with the wiring under the dash. The closest I get to your issue is that I occasionally get a small stumble/backfire when the engine isn't fully up to temp. Have yet to iron that issue out yet, but it's nowhere near what your problem is. Link to comment Share on other sites More sharing options...
Jeep Driver Posted April 9, 2015 Share Posted April 9, 2015 Check your battery cables and grounds again. Link to comment Share on other sites More sharing options...
Dom U Posted April 10, 2015 Author Share Posted April 10, 2015 Check your battery cables and grounds again. Checked them over and over. And all the wires are all brand new. Link to comment Share on other sites More sharing options...
Marine1Texas Posted April 10, 2015 Share Posted April 10, 2015 Since it happens when you brake and you say tail lights and brake stuff is clean, I would check ECU plug and wires. If all seems good follow those wires to the throttle body. Auto is also plugged to throttle position sensor and wiring could be shorting out or not adjusted right. Unlike manual when you apply brake the throttle position sensor needs to apply extra information to keep engine at right rpm. Use cruisers tips to help test the throttle position sensor. Link to comment Share on other sites More sharing options...
Dom U Posted April 11, 2015 Author Share Posted April 11, 2015 Since it happens when you brake and you say tail lights and brake stuff is clean, I would check ECU plug and wires. If all seems good follow those wires to the throttle body. Auto is also plugged to throttle position sensor and wiring could be shorting out or not adjusted right. Unlike manual when you apply brake the throttle position sensor needs to apply extra information to keep engine at right rpm. Use cruisers tips to help test the throttle position sensor. Did this last night, all seems well used cruisers tips. Electrical gremlins ): Link to comment Share on other sites More sharing options...
WiscoXJ Posted April 11, 2015 Share Posted April 11, 2015 start unplugging stuff and testing. if its a ground or wiring issue if you disconnect the circuit and the issues goes away you know what to fix Link to comment Share on other sites More sharing options...
Dom U Posted April 13, 2015 Author Share Posted April 13, 2015 Still haven't found the problem. Could it be the IAC? Iv cleaned it up pretty well already but could it be damaged? Would it even cause the problems I'm having? Link to comment Share on other sites More sharing options...
Dom U Posted April 13, 2015 Author Share Posted April 13, 2015 Just had her in park idleing and was playing with the throttle to see how she reacted to things. On a longer 20 seconds of steady rev did okay. If I do short spurts of reving it up it stumbles to a very very low idle and nearly dies. If I do it about 3 Times in row it dies. Link to comment Share on other sites More sharing options...
Dom U Posted April 18, 2015 Author Share Posted April 18, 2015 Anyone think it could be the IAC might have to pick one up tomorrow from Napa. My cat seems to making a slight rattling noise how can I test it?? Thinking about eliminating the c101 Link to comment Share on other sites More sharing options...
cruiser54 Posted April 18, 2015 Share Posted April 18, 2015 Do you realize that the ground behind the driver's side taillamp is for not only the lights but the fuel pump? Is there some hay-okey trailer wiring at the rear? Link to comment Share on other sites More sharing options...
HOrnbrod Posted April 18, 2015 Share Posted April 18, 2015 Did this last night, all seems well used cruisers tips. Electrical gremlins ): If you used and understood how to use Cruisers tips, you would never have mentioned electrical gremlins. No such thing mate. Link to comment Share on other sites More sharing options...
Megadan Posted April 18, 2015 Share Posted April 18, 2015 Did this last night, all seems well used cruisers tips. Electrical gremlins ): If you used and understood how to use Cruisers tips, you would never have mentioned electrical gremlins. No such thing mate. Oh? I've done ALL of Cruiser's tips. I still have electrical gremlins. ;) Granted, I know where my gremlins lie. It's just a matter of taking the fuse block apart and cleaning it up and resoldering things. Link to comment Share on other sites More sharing options...
HOrnbrod Posted April 18, 2015 Share Posted April 18, 2015 Do you also have boggarts and henkies? Link to comment Share on other sites More sharing options...
Megadan Posted April 18, 2015 Share Posted April 18, 2015 Nah, just trolls. They like to make my life worse right when it's least convenient. Like my tail lights shutting off randomly. Jiggle the fuse and they come back on lol Link to comment Share on other sites More sharing options...
Comanche County Posted April 19, 2015 Share Posted April 19, 2015 Sounds like you need a new fuse box or new fuse terminals. I think its easier to remove the dash and replace the whole dash harness and fuse box, at least I can do it faster and more comfortably than contorting myself and repairing the fuse block in place. There's a couple of good links in the DIY section. http://comancheclub.com/topic/18588-xj-dash-harness-to-rear-mj-harness-wiring-guides/?hl=dash+harness, I recently swapped a 89' auto XJ dash harness into my 89' manual MJ and it fixed just about everything. The interior dash lights are nice and bright now, B pillar lights work again, wipers are nice and strong, radio reception is better, starts better, runs better, brake lights and turn signals work again. A rotted fuse box can definitely cause all sorts of problems. After owning the MJ for so long I had just gotten used to everything being like it was, now it almost seems like a new truck. It also added the headlight delay feature and XJ rear defrost/wiper timer and wires and many more power terminals in the fuse block. I'm also borrowing mfpdm's ideas about using the rear defrost power supply for bed rail lights. I'm gonna use the XJ factory dash switches for fog lights, bed rail lights, rock lights and my OBA system. Now I've pulled another 88' XJ auto harness and I'm about to do the same thing on my 87' MJ. Link to comment Share on other sites More sharing options...
Comanche County Posted April 19, 2015 Share Posted April 19, 2015 Link to comment Share on other sites More sharing options...
Dom U Posted April 23, 2015 Author Share Posted April 23, 2015 Did this last night, all seems well used cruisers tips. Electrical gremlins ): If you used and understood how to use Cruisers tips, you would never have mentioned electrical gremlins. No such thing mate. I did use and understood, I had some help with the TPS other than that pretty much straight forward. Do you realize that the ground behind the driver's side taillamp is for not only the lights but the fuel pump? Is there some hay-okey trailer wiring at the rear? Yes I do reapize that. There are trailer lights I installed myself and did it all properly. Link to comment Share on other sites More sharing options...
cruiser54 Posted April 23, 2015 Share Posted April 23, 2015 So it's all good now? Link to comment Share on other sites More sharing options...
Dom U Posted April 23, 2015 Author Share Posted April 23, 2015 So it's all good now? Its driving a lot better after eliminating the c101, it did its slight back fire once didn't die. The lights dimming is fixed. I feel like iv lost a lot of power and like my engine is trying to hard. Link to comment Share on other sites More sharing options...
cruiser54 Posted April 23, 2015 Share Posted April 23, 2015 So it's all good now? Its driving a lot better after eliminating the c101, it did its slight back fire once didn't die. The lights dimming is fixed. I feel like iv lost a lot of power and like my engine is trying to hard. Let's regroup here. Have you tested the fuel pressure? Link to comment Share on other sites More sharing options...
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