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Jeep Sputtering Problem

1K views 4 replies 2 participants last post by  sik4wheeler 
#1 ·
So my 4.0L 89 xj will idle fine but, when I apply a little skinny pedal it will sputter, spit and backfire. I can pump the pedal and get it to rev past 2k and as long as I hold the rpms up it will run fine but as soon as I let them drop and try and give it a little gas it will have the same issues. I have checked the TPS, MAP, Fuel pressure at idle is 34#, injectors are getting a good signal and the dizzy cap is sending great spark to the plugs. The jeep has a new tps, iac, cps and fuel filter. The plugs, cap and wires are fairly new and in good shape. Whats going on with it. I have been working on trying to get it running right for the past three weeks. Pleasehelp I am trying to get back on the trails. Thanks guys
 
#2 ·
I would put a timing light on it to make sure it is where it should be. I think fuel pressure is supposed to be at 29psi at idle and go up with lack of vacuum. Did you adjust the tps when it was installed? It is a pain in the ass and don't ever change the throttle plate angle or it screws up the iac, maybe vacuum leak to map sensor. some where on pirate there is an entire renix injection manual. might want to back probe the o2 sensor to see what the mixture is like just to see if it's way off.
 
#4 ·
I put a timing light on it and it was near 16 degrees. I have made some timing adjustments and am not sure where i am at now. Also, The block, head, intake and throttle body are from a 94 H.O xj. I put the Hesco TPS adapter on and I have adjusted the tps to spec. I messed with the jeep some more and it will run okay some times and not at times. I can now rev it up past 2k smoothly. It will sputter at times reving up slowly off of idle and sometimes not. Occasionally the rpms will drop if I tryu and bring them near 1800k rpms. Thanks for the help.
 
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