92 4.0 SURGING AND HARD START

JSJJ388

JSJJ388

GREEN GREMLIN
Joined
Aug 31, 2016
Location
HAMPTONVILLE, NORTH CAROLINA
I put a new motor in my 94 ZJ a couple months ago. have been having issues ever since. It is a pain to start, my ignition switch went out and it doesnt have the spring loaded start area, ie when you turn it all the way forward there is no spring and the engine doesnt turn over. for testing purposes, i tapped the wires needed to start it until I got a new switch. it takes anywhere form 1-15 tries to get it to crank and run. it makes a sucking sound through the throttle body and runs rough. After a few tries, it catches and runs like at top at idle. It has a skip at ~2500-2800 RPMs. I have replaced TPS, CPS (casualty of motor swap), MAP, plugs wires and dist, throttle body, and fuel rail. Still hard to start and still skips. Replaced switch and it made no difference at all. So Im thinking of going to a switchless ignition for simplicity sake and neat factor. Still have no clue why its hard to start and why it skips. Anyone have any ideas or dealt with it before?


I drove to work the other day and after about 20 minutes on the highway, it started surging and bucking under load. Cut it off and restarted and it drove another 10 mins fine. Same thing on the way home. Poked around and found the casing on the o2 sensor wires was torn, replaced it since the symptoms fit. No luck. Drove up to the lake and after 20 mins on the hwy it started bucking. Pulled over and restarted it was fine. on the way home I took backroads. Drove 45 minutes and it didnt buck and surge like on the hwy. Im stumped. Any thoughts?
 
I had some similar issues on one of my '97 ZJ's but they were constant rather than the intermittent ones you describe. A ECM was the solution for mine at the time. I've had other starting issues on my other '97 ZJ that were related to the harness connections where it plugs into the ECM. Event though the connectors "clicked" in one was still not seated but a large zip tie fixed that and all has been well for about 6 years. Given what you have tried a ECM might be a good next step.
 
adamk said:
Is this with the engine running or just letting the pump prime the system?
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I believe that was running. But that's been a few years ago now.
 
adamk said:
Wow, I didn’t realize this was a thread raised from the dead. Ignore everything lol
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Its all good. I raised it from the dead as Im trying to get the jeep up and running again.
 
Mine was doing that but it was the distributor.... my cap was toast and gouged heavily with burn marks & the bearing was worn out also on the distributor shaft!
 
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