4.0 liter, 156000 miles, Auto trans,
It dies while driving. RPMs drop and it dies. Then starts right back up.
These things have already been replaced
cam shaft sensor
crank shaft positioning sensor
fuel filter
Plugs/Wires/Distributor Cap
Sounds like you’ve replaced parts that are often the usual suspects. That can get expensive fast, if you guess wrong.
On weird intermittent problems like this, you’re going to have to instrument parts of the car, just to isolate the problem.
I’d start with the basics by hooking a 12V bulb between the common connection of the coil and ground.
That point should be 12V so should be on when the key is in the on position. Rig something up with something that could stand being in the car while you’re driving with proper contacts, proper insulation so it doesn’t chafe and short, etc.
Place the bulb somewhere sticking out of your hood where you can keep a close eye on it while driving/testing. When the car stalls, see if the light flickers off.
If so, trace it back.
You may find the problem is your ignition switch.
Im not sure i completely “common of the coil and ground”
Thats: Im not sure i understand “common of ground”
Oh wow. That should be: Im not sure i understand “common of the coil and ground”
If it were the ignition …you mean the switch itself…where you slide the key in? and could a heavy key chain cause this?
Sorry, I turned off my computer for the evening after I posted that^.
Didn’t mean to be vague and can see now how my comment could have confused you:
There’s a common connection on the coil that supplies both 12V to the primary and secondary.
Note that “Common” does not mean ground in this case. It is a common connection. Turn the car on but don’t start it. In the position right before start, you should see 12V on that connection.
You hook your test light fixture between that point and ground so you can see that 12V is indeed there when you expect it to be there, like when you’re driving. It should only not be there if the ignition switch it turned off.
Since your problem is intermittent, this would be one way to see if that voltage not being there is your problem.
Note I’m NOT suggesting you start replacing the ignition switch but merely mentioned that could be the cause of the problem if you don’t see 12V on the coil.
There are, of course, quite a few connections between it and the ignition switch. Don’t throw parts at the car, if you can help it. It gets expensive and frustrating quickly.
Ok i follow that.
Question: in my research ive been doing online i found possible PCM faulty. This morning when looking at the jeep i found under the hood. "The following modifications have been made- PCM#4886692. Then in my reading i found "Back off the two screws under the three connectors on the PCM module, they are about .5 inches long #6 machine screw, replace with .25 inch. Worked on my '97 Laredo.
Any thoughts on that?
I have no idea why they’d want to replace screws. Maybe the longer ones penetrate whatever is mounted too deeply and short something out? - that’s just one guess.
That’s what I came up with. I think that dog don’t hunt.
The coil thing you suggested…I can take a 1156 or any bulb of that nature and connect one wire to power on coil and ground anywhere?
Jeep also backfired FYI
If light goes out when jeep dies it means bad ignition?
Another question: if “flash chip” in computer is bad. Will check engine light come on?
I checked electric connections at computer and noticed its a remanufactured. Makes me think it computer…again
Any low power light bulb will do - a 1156 is very visible so that’s a good choice.
I am sure it would play havoc with the system but what makes you think the flash is bad?
Found bad flash chip in jeep forum, was causing same problem 1yr newer jeep
I’d be very reluctant to suggest a chip is bad without any evidence, tho. Is that a common part to step into the weeds according to that forum, then?
What evidence would there be?
Well, that’s what I’m asking. I rarely replace anything unless I know it is bad.
Unless you happen to have another one laying around, just blindly replacing parts gets expensive.
Try that lightbulb thing and see what we learn.
Ok. Say it light bulb goes out when it dies. Then what?
If the light goes out the most logical suspect for the cause of the trouble would be the ignition switch contacts.
Yup. That, or a connection to the ignition switch.
That supply voltage is supposed to be there with the key on.
Thanks guys. I will be rigging a light as soon as she gets back from the muffler shop
I just read through some of the paperwork found in the glovebox. Ignition switch has already been replaced