JSJJ388

Ok, so my jeep (94 zj 4.0) has started stalling at random times going down the road. I pull over, put it in park, cut off, take key out. Put key back in after a few secs and it cranks like normal. It sits and idles fine, I can never predict when its gonna stall though. The only time I know it will stall is if I put it in 4 lo and hold the brake and give it some gas it stalls immediately. Wont do it in 4 hi.

My fiances car did something similar a while back and it was the throttle body. Could this be it?

I tried unplugging what I think is the TPS and it spits and sputters as I would expect, but when I unplug what I believe to be the Idle Airflow Sensor it has no affect.

Any thoughts on what would cause this or where to start on figuring it out?

jeepdewd

After I replaced every sensor several times the stalling became more often and then after the second time my muffler exploded from the backfire that eventually showed up, I took to a mechanic who mainly repaired jeeps
They ended up repinning a bunch of wires going into my computer and they even found a couple broken ones and replaced those as well. I have not had an issue since

peep

Sounds like fuel pump.
Have had similar symptoms on my 89XJ and recently 95 ZJ.
Driving along, shuts down, stop, restarts.
Replaced fuel pumps on both.
I understand it's frustrating when it fixes itself, and you can keep going.
When something breaks for real, then you know what to fix.
Perhaps you can check fuel pressure. Often a failing pump will provide low pressure and then fail completely.
Of course there is also the Crank sensor. A common fail item. Worth checking the CPS output. It is also an item that can get weak prior to full failure. Cruiser 54 has an excellent procedure on testing.
Just sayin, it's going to take some investigation to narrow down to the real cause.
Post any additional sypmtoms or occurances that happen.

peep

Sorry, my bad, you found bad wires and jeep is cured.
Was this repinning at the under hood connetors?

dave1123

That's pulling the connectors apart and replacing the pins and socket ends of each wire. It's labor intensive and finding the right parts is difficult. Sometimes you can get away with just cleaning them and pinching the female connectors for a tighter contact. Most sensors operate on 5 volts so contacts are critical.

The CPS (crankshaft position sensor) is a Hall-effect switch which senses changes in it's magnetic field caused by objects passing by it. Mopar sensors are made with a rare-earth magnet and aftermarket ones generally are not. The strength of the magnet determines how responsive it is.

JSJJ388

Replaced the CPS and now the ol gal runs like a top.

peep

My 95ZJ contiues to also fail unpredicatbly.
My fail on the fuel pump replacement, misdiagnosis, at near 400Kkm it probably would have needed one soon enough.
After a couple shut downs in bad weather conditions. (Ive been lucky on the restarts, probably borrowed time)
A new CPS ordered, will pick it up Sat AM, dog and I will install.
As a note, my ZJ is 4.0L w/ Auto 46RE trans.
The CPS is on driver side, single bolt type.
Can see it clearly, although narrow passage way may be too tight for my arm.
May have to undue front drive shaft and trans shift linkage to better access.
Or convince wife to reach up in there????
Good to hear your runnin like a top.

dave1123

A bit of advise? Take out the crossmember bolts and lower the trans down. It makes the change MUCH easier. BTW, the electrical connector is on the passenger's side.

OOPS!....95 still had mechanical trans linkage. You may have to disconnect that first. My 2000 shifts by cables.

peep

JSJJ338, wow, change my CPS today, what a pita! I share condolences!
FDragon, thanks for the heads up on the connector on passenger side.
What worked for me was jack drivers side tire about 4" off ground, jackstand and remove tire. Makes enough space to be under truck but still reach the CPS with arm length.
If I lay parallel with the truck I could reach up between LCA and front driveshaft, just enough to get fingertips over the top of bellhousing.
95 CPS on 4.0L w/auto is drivers side and held with single bolt, 11 mm socket.
Couldn't get a decent pick but with lots of trouble lights I could see it.
Lots of extensions and a swivel on socket to reach, threaded extensions above TCase cross member for best approach angle.
Once the bolt is out (don't drop it), used a long (2ft) screw driver to push the CPS upward from underneath, it is tight between the bellhousing and the tunnel but with some work and persuasive conversation, it does make it's way out.
Pulled it thru by the wire to the passenger side.
Fed the new one across from the passenger side and from underneath with fingertips and that thin 2ft long screwdriver, worked it around to get the tip started back into the hole, then swiveled with the long screwdriver and pushed downward with the fingertips to seat and get bolt flange aligned over hole.
A little tape across the 11mm socket keeps the bolt head wedged in there tight, feed up and get started into hole, click on the ratchet and tighten it home, socket will pull off and tape will fall down.
Then feed the wire across top of trans toward passenger side. Access from top on driver side is terrible, you can see stuff but very tight.
Reach around back of cylinder head at passenger side and grab the wire, pull across and plug back in.
Fired up.
Did the Cap n Rotor and air filter also. The rotor and internal cap had lots of errosion and were due. Yes it was a Fram air filter for all the Fram lovers.
Sorry, not many pics, but it was a dang cold cold day.
Light PTouch mechanic gloves help with handling the cold.
My helpers didn't help, Nyala stayed snuggled in the straw and 8 wk puppy Clark doesn't have the coat for the cold.

dave1123

Here's an old electrician's trick, too late I know, but tie a strong string to the connector BEFORE you pull it harness out, then tie it to the new one!

Here's some pics on other ways to get to it. Again, too late! LOL!

JSJJ388

I was able to reach to my cps fairly easily, but I have skinny arms. once I found the right socket all I needed was a 18" extension and a spring swivel and it was off in 2 minutes. had to run back to parts store because they sent me a 2 bolt one. then took all of 5 minutes to find the hole and bolt it in. I dont see what all the big hubub is all about. I didnt find it hard at all.