CherokeeCountry

Just bought a very clean-bodied 93 ZJ (just for the good body and paint, my 5.5" LA's and 35's are getting put underneath it off my other V8 93) and I'm trying to at least get the engine running on the new girl before the big swap to see if I've got a decent 318 left over (And to get it home...) It doesn't want to stay running. Here's where I am so far: I removed the anti-theft terminal that was spliced in at the wire on the ignition coil, had the battery and alternator tested at auto zone and both were serviceable. Reinstalled those, checked spark at the coil, went inside, and noticed I heard a blinker-click which turned out to be a "security" light flashing on the dash. Thinking it's OEM then. Anyhow, I played with the key fob lock switches and got the light to stop flashing, put the keys in and started the motor right up. Quick crank, immediate start, went straight to 800rpm, revved nicely and responded to throttle, so I let it idle for 20 minutes to see if it would get to temp, leak, etc. Coolant cycled great, T-stat opened, motor got to temp (205 ish), 14v, 60lbs oil pressure, good fuel, but when I put the vehicle into drive, I was only able to keep it in gear and play with the brakes and steering for about one minute, then it started to idle super rough, barely run, backfire, and no throttle could save it. Almost like it lost timing suddenly. It would carry on horrible like this for about 30 seconds and just struggle if you let it. So I shut it off, and attempted to restart it. It would want to fire, then just sputter and backfire some more trying it's hardest to find an idle and run. So next crank, I did a tiny shot of starter fluid in each side of the TB, and it would finally rev and respond a little to the pedal before dying completely a second after. So: I'm thinking Crank Position Sensor and possible Neutral Safety Switch, and a fuel filter as a starting point? (I'd throw in TPS and IAC, but it ran/revved so beautifully for almost half an hour before it died.) Since it responded to the starter fluid, maybe a fuel issue? (I have great pressure at the rail test port even after it dies so that's confusing) but this Anti-theft also has me worried. Could it be spliced into a hundred other places under the dash and cutting something off once in gear? What do y'all make of this?!?

MD9NYC

Definitely sounds like a fuel problem if it is starting with fluid in the TB. I am going through the exact same thing with my 98 ZJ 4.0. I changed the pump yesterday to no avail. Now that I'm getting fuel at the rail, it must be the injectors not getting power. Maybe your ASD or PCM. I'm still trying to decipher.

Note that I also changed the Crankshaft Position Sensor and that didnt work either. I later founds out that if the engine starts with the use of fluid, then it's not the crankshaft position sensor (wish i would have known earlier).

Maybe the camshaft sensor? I'll keep you posted if I get mine going.

Cleman Simpson

Sounds to me like it has water in the gas tank. If it ran fine for twenty minutes you probably used up the old gas in the tank down to the level where the water is stratified on the bottom of the tank.

XJRed96

this generation jeep (goes for both posters) can be a ***** to relearn an idle. once you get the jeep to operating temp by just letting it idle, if still possible, then turn it off, if you can't idle it just continue on ->. disconnect one or both battery cables, and AFTER you've disconnected one or both cables touch them together, if you need to use a screw driver to complete the circuit that works too. Leave it like this for 2 minutes. Re connect battery cables. And then start the car again. wait a minute or two once it's running to let it relearn some basic adaptions. Hopefully you have a normal jeep again. If not pull the idle air control and make sure it operates. you can use jumper wires across the terminals. I'm assuming you've already scanned the OBD for any faults(the 93 might be a little tricky but it might have an OBDII port. )

Also if you've got a slow or weak crank it may flood it out a little bit, and if this happens and you need to use the pedal to get it started this will cause the ECM to relearn a false idle and can be a ***** to keep it running. once you've ran it long enough to clear any excess fuel from the engine/intake and recharge the battery a little bit restart at the disconnecting battery again.

CherokeeCountry

Well, I'm pretty sure I purged the electrical system when I pulled the batt and alternator off, but I'll give it another shot to make sure I completely reset the ECU. But I'm definitely leaning toward fuel myself. I'll change the filter, see if I can't learn some more about what's going on with the fuel system. Only thing is that when I checked the rail after it died I still had beautiful clean fuel spouting out.. anyhow, I forgot to mention I did pull a code off of the OBD1 with the old "on off on off on" trick and I was reading code 21- "O2 sensor neither rich nor lean reading". Could a faulty downstream o2 sensor cause this much grief? Pretty sure I don't even run a downstream on my current v8... hah!

XJRed96

did it actually say downstream 02 sensor? or did it just say o2 sensor? try unplugging the sensor. once the vehicle warms up and switches to closed loop a faulty o2 sensor could cause poor running by messing with the fuel trims, and severely limiting the amount of fuel the vehicle is getting. You can try unplugging the sensor and see if it makes a difference. if it does, replace the sensor.

CherokeeCountry

No, I'm sorry, it just said "o2 sensor, neither rich nor lean" and then the end of test code. (Check engine flashes that little morse code deal to you on the dash). Thanks for the idea XJRED96, I wasn't sure how it would behave if I just undid an o2 sensor on these electronic messes. I'll get underneath her, change the fuel filter, then troubleshoot the o2's. Feel free everyone to keep posting ideas, all the info I can get is great and will probably help me diagnose/learn something about my issues as I go down the list! I appreciate it!

XJRed96

dont get me wrong it's not going to run amazing without it plugged in, but it should default to a "safe home or Limp mode" setting that should keep it running when it would normally stall.

CherokeeCountry

Well, I towed it up to my friends property, was able to start it up, drive it off the trailer (First drive ever) and do a couple loops in the lot. When I went to park it, I drove into a spot, put it into park, and just kind of looked down to listen to the idle. Out of the corner of my eye I saw the ground just barely moving, hardly enough to notice. Paid some attention, realized it was definitely still moving (extremely slow, maybe a few inches in 30 seconds) even after double checking the tranny was in park, and then it sputtered out and died like usual. So, even in park she slowly creeps along wanting to be in gear still, then dies. I didn't think much of it at the time, but while doing my little test loops when it was in gear and driving I heard a louder than normal "whine" almost like a power steering pump makes coming from the trans tunnel that changed pitch with the throttle. I know this means tranny for sure, but past that, my expertise ends. Does this narrow it down at all guys? I need this thing ready for "Blessing of the Jeeps" here in Michigan at the end of April if I can help it!

CherokeeCountry

Did some troubleshooting on the engine today, but nothing new and no idea on the "rolling in park" issue still. Tested the relays for the Auto Shutdown, Starter, and the fuel pump (for some reason I get fuel at the rail and a good clean start, but if I shut it down or let it run for about 25 minutes it'll die and not restart and has no more fuel pressure) and they are good. I was thinking maybe crank or cam sensor, but I throw no codes, and I can hear the ECU grounding and engaging both the starter and fuel pump relays under the hood when key is in "ON" or "ACCESSORY" position which from what I read online means the computer got good signal/comms from the cam and crank sensor, then grounded out the relays so they can engage and allow the fuel pump and various accessories run. I don't hear the 2 second fuel priming cycle that the ECU and pump are supposed to start when the key is in the accessory position, and have no pressure on the gauge at the test port even when cranking. So is it pretty safe to assume fuel pump here? Could it be that factory anti-theft or ASD? What do you guys think? PLEASE HELP!