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1991 wrangler yj/4.0

1K views 10 replies 4 participants last post by  country6068 
#1 ·
Hello everybody, hard to crank, must hold fuel peddle to the floor to get it to crank. really rich as black exhaust rolls out tail pipe. when it cranks it takes a few min to clear up, once its cleared up I have a high idle with a hesitation throttle response.
checked the codes and get a 12 and 55, removed o2 sensor and tested on the bench. Looks like a .014 while heating with propane. I think it should be 1 volt. What else should I be looking at???
Any ideas?
Thanks
 
#2 ·
You should never have to hold the accelerator to start a fuel injected engine. The accelerator pedal supplies the engine with air. Not fuel. If you have to manually supply the engine with air during start up, then the Idle Air Control valve is malfunctioning. Either the IAC motor is not functioning or the valve is gummed up and not moving smoothly. The IAC valve is located on the throttle body and has a wire harness.
Remove & clean the valve with carb cleaner and verify that it opens when you switch the ignition key to on. (You can do this before reinstalling it.)
Report back if you still have issues.
 
#5 ·
Removed entire throttle body last night, removed IAC and cleaned plunger, replaced throttle body gasket, replaced o2 sensor. Installed all components and turned key to on position, butterfly did not open on its own. I am thinking I have a bad TPS sensor.
will remove tps sensor and plug in wire harness and turn on key to see if there is any movement. check engine lite came on and checked codes (12,13,14,24,55).
 
#6 ·
Update: removed battery connections and reconnected after short while, checked codes again (12, 55), cranked motor, still has nasty hesitation, High idle (1100rpm), try and open throttle easy and stall. Open throttle to extreme and hesitation then rev's up. shut it down after 10 min, crank short while later and it just turns over, hold peddle to the floor and will crank but seems like it flooded but will crank, takes a few to clear up but idles nice hitting on all 6 with high idle (1000-1200rpm)
 
#9 ·
Bought this Jeep as basket case, loaded this thing in the back of my truck in boxes and baskets. Wire harness was hacked, no gas tank or pump, no gauges, body on a trailer, literally a basket of parts. Not sure what has been done before I got it running.
sadly I had it running very well, parked last saturday and wife tried to start Sunday and would not crank.
 
#11 ·
Wow, after unplugging all connectors through out engine bay I have found one with bad corrosion over by fuse block. only one I have found with green nasty corrosion, after cleaning this connection jeep runs great again.
No hesitation, no misfires and best of all it cranks with out touching fuel peddle.
Something so simple, well thanks for all the suggestions.
 
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