Stalling, hot no start

[mongolchuck]

Alright, this might be a little long but the more info the better right? 1986 XJ with 93 4.0/ax15 from a ZJ. About 2 months ago I was running into some drivability issues. It will occasionally die when coming to a stop and i disengage the clutch. I can pop it back out in second and it fires right up. Cleaned and checked IAC and ended up replacing it because I stretched the spring. Reset idle and all but still has same issue. Then about a month ago it died on my way to work and wouldn't fire up. Fuel pressure was good and I could smell gas so I was thinking no spark. Did full tuneup and changed the cam pickup in the dizzy. Runs better but still will die sometimes while coming to a stop light. Then a week ago I am going to few stores, leave the last one and it won't fire. Turns over fine but just won't fire. It does finally start 3 hours later about halfway through towing it home. Figure it's time for crank sensor. Change it and seems to be fine until tonight. Drive to a meeting, shut it off and crank it over right away to test. Nothing, crank no start. Whatever. Let it cool for an hour and try it again. Crank no start. Disconnect Bart for a bit and reconnect. Fires right up. Driving home it begins cutting out intermittently. Tach goes to 0 then back up then 0 and so on. Definitely points to the cps going out. Pull over mess around with coil and cps connectors, check plug wires, all is good. Straightens out and drives perfect rest of the way home. No dying at lights, no bucking. Get home shut it off and it fires right back up. So what is my issue? I think I need to go back to the good CPS or go mopar but I'm also leaning towards the computer having issues. Any help would be appreciated.

 

[Hypoid]

Tugging on the wires and the problem goes away??? Time to clean and reinspect all those connections!

 

[mongolchuck]

Well my new CPS is garbage so I'll spend the extra coin and get a Mopar if I can and see what that does. Thought Delphi would be decent.

 

[blu3fan]

FUEL PUMP BALLAST.... I am not sure if you have one in that early a jeep.
if you do. throw it in the dirt. shoot it. then solder those two wires together.
I have had the freakin exact issues to the T dude.... your speaking about the last two years of my life.

and the no start issue. no crank. thats the neutral safty switch.
Next time it happens.
Press the shifter fowards. past park. up. gently. while doing this. crank the engine

 

[blu3fan]

when you are messing with your cps. you are wiggling these wires. and its fixing your issue. but the bad crappy connections are still there.
is what I suspect.

 

[mongolchuck]

Thanks for the replies. I don't have a ballast resistor. I did get a mopar CPS and finally got around to putting it on yesterday. I haven't taken it out and about yet being it's Christmas but have let it run some. It will idle ok after running for a bit but seems to be missing in mid rpm range and will nearly die and sometimes die letting off the gas. I will investigate that further when I get a chance but I need to do an idle relearn.

 

[BenWheelin]

FUEL PUMP BALLAST.... I am not sure if you have one in that early a jeep.

My 86 has one, but it came with everything else from a 92. The way I built mine, it's a 92 from the dash forward, the tub is irrelevant. When asking a technical question, I would use the year pertinent to the parts in question.

 

[mongolchuck]

I know I don't have a ballast resistor. I bought one and put it in when I was cleaning up the bay from what the previous owner did for the swap. I didn't like it and everyone said it wasn't necessary.

 

[BenWheelin]

So you're running the ZJ ECM?

How is that wired in? Where? I used a complete late model wiring harness on both sides of the bulkhead, and only cut the body connectors off to connect it to the rest of the Jeep. I have the whole late model dash harness, and all splices were soldered.

You changed the crank position sensor, after you changed the cam position sensor, what was the play like in the distributor shaft?

 

[mongolchuck]

Actually doing more research the engine and ecm are from a yj. I changed the cam sensor during the full tune up a month or two ago and changed the crank sensor a few weeks after that. The dist bushing felt fine and timing is right on. I really just need to take this thing on a decent drive to get the computer some time to recalibrate and see if the mopar sensor makes the difference. It's tough to do stuff when it's below zero outside

 

[blu3fan]

Try the idle air control valve?
It does more than you would think.

 

[Ecomike]

How do you know the new CPS or old one was even the problem???? Did you test it?

Have you tested anything???

The old pre 91 jeeps were notorious for ground wire issues in the entire sensor and controls ECU harness assy and the block connection near the oil dip stick.

You need to get a fuel pressure gauge on their and a volt meter (or ohm meter or both) and test every sensor and ground wire for loss of ground quality or loss of voltage while wiggle the wires/harness, and wandering fuel pressure.

O2 sensor or its wires may be going bad, may be damaged and randomly grounding out!!!!

You may have a bad or dirty temp sensor, coolant or air temp sensor.

The Vacuum line to the MAP may be leaking vacuum

The TPS may be bad or the wiring /connections to it making poor contact, or BOTH!!!

What does each spark plug look like?

The HV coil or ICM module under it may be going bad

Have you tested the TPS signal from idle to WOT for bad noisy spots in the output signal. Like at idle!!!

When you have a no start does it have spark!!!!!

Are the injectors firing while cranking in a start situation.

 

[Ecomike]

Computer recalibration is not an issue!!! If it is, just disconnect the Battery + cable and ground it for 15 seconds. That will wipe out any garbage data/memory.

Actually doing more research the engine and ecm are from a yj. I changed the cam sensor during the full tune up a month or two ago and changed the crank sensor a few weeks after that. The dist bushing felt fine and timing is right on. I really just need to take this thing on a decent drive to get the computer some time to recalibrate and see if the mopar sensor makes the difference. It's tough to do stuff when it's below zero outside