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88 running rough

O

Osmin C

NAXJA Forum User
Location
SoCal - North Hills
My 88 4.0 auto runs rough, before it was only when it was cold but I replaced the O2 sensor and even after it warmed up it still runs rough. At least before after it warmed up it would run ok. If I try to accelerate it wont pass 1100 rpms. The motor shake and runs really poorly. Any suggestions?? Thanks all.
 
plugs wires cap and rotor would be where I would start. SOunds as if you've got a miss of some sort, arcing in the cap would be my first suspect.
Pull the cap and look to see if there's marks on the inside, that would be an indicator of it arcing across the cap.
 
Osmin C said:
My 88 4.0 auto runs rough, before it was only when it was cold but I replaced the O2 sensor and even after it warmed up it still runs rough. At least before after it warmed up it would run ok. If I try to accelerate it wont pass 1100 rpms. The motor shake and runs really poorly. Any suggestions?? Thanks all.
Click to expand...
Whats your fuel pressure?
 
Unknown, sounds dumb but I just started to try to diagnose the problem. Honestly Im sure that I could have tried a bit more to try to figure it out on my own but I figured some suggestions on where to start couldnt hurt.
 
Osmin C said:
Unknown, sounds dumb but I just started to try to diagnose the problem. Honestly Im sure that I could have tried a bit more to try to figure it out on my own but I figured some suggestions on where to start couldnt hurt.
Click to expand...
Other than the stuff like Plugs and wires if due then start with fuel pressure, you need 31# even when it starts to miss. You could have a plugged filter.
 
Check the MAP (manifold abs pressure) sensor. The tube connecting it to the throttle body may be disconnected or stopped up. Also the sendor could be bad. I remember I had my 88 XJ run bad when I changed injectors and forgot to hook up the MAP tube.
 
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