90 xj starts and idles but backfires and wont rev


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Old 05-28-2011, 06:20 PM   #1
zman32006
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Default 90 xj starts and idles but backfires and wont rev

Got a 90 xj and just put in a 89 4.7 Inline 6. theyre both renix so everything hooked right back up. it was running fine for a day or so but I changed fuel rails, injectors, and did a tune up on the plugs wires and put a new battery in and now it will start and idle perfect with an occassional skip but as soon as any throttle is applied it wont rev at all and backfires. also when its idling the CAI hisses like its WOT but its idling at 500-1000 and once throttle is applied it stops hissing. any ideas? Ive checked the TPS and adjusted it both way and replaced the CPS as well as everything else I listed.


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Old 05-29-2011, 06:54 PM   #2
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got an update. it idles near perfect now and I can rev it up to 1500 rpms, but as soon as it hits 1500ish it backfires and wont rev any higher. I adjusted the IAC, TPS, CPS, and it no longer hisses through the intake as bad and I also fixed a vacuum leak in the intake.


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Renix 4.7L, homemade Roof Rack, 4" lift, trimmed fenders, 33's, cb, 10 meter radio, power inverter, herculinered floors, 2 12" subs, 1600 watt amp, custom bumpers, high amp alternator, homemade sway bar disconnects, rockers, more and more to come
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