tbrunke

First off thanks to everyone on here for the great tips and tech write ups.

I have a 1987 Cherokee 4.0, automatic. I have an intermittent stalling problem, when it starts to stall, sometimes it dies and sometimes it doesn't. Everytime when it stalls when I am trying to diagnose the problem the Power Latch Relay starts clicking. Please help!

I have replaced/fixed recently:
Upgraded to Mustang 5.0 litre 19lb fuel injectors
IAC
TPS (yes it is adjusted correctly)
MAP Sensor
Exhaust/Intake Manifold Gasket and fixed exhaust leaks.
CPS (Crankshaft Position Sensor)
Cleaned the throttle body and the intake manifold.
Plugs, wires, cap and rotor.
O2 Sensor
Knock Sensor
Coolant Temperature Sensor
Upper and Lower Radiator hoses
Crankcase ventilation
New ignition coil
Wired an extra ground cable and did another ground just for the TPS
Cleaned the C101 connector 3 times
Cleaned all grounds and wire connectors in the engine bay
New thermostat
All relays are good.
Fuel pressure is within correct parameters
More but that is all I can think of at the moment.

I can only think that it is either a bad ECU, a tired ignition control module or a short somewhere. If anyone knows what would cause the Power Latch Relay to always click when this happens PLEASE let me know. Thank you!

Gee oh Dee

Not familiar with a power latch relay.

When it stalls does it restart right away?

Also, keep in mind (especially with the number of new parts you tossed at it), replacement parts sometimes don't work right out of the box. Something you replaced may still be bad.

Radi

As I understand it, the power latch relay supplies power to the ECU after you turn off the key so the IAC can reset itself. It's powered through a delay circuit elsewhere in the ECU.
Perhaps check the ECU connectors and wiring for trouble?

cruiser54

Have you tested the CPS output? Post 7

Post 3?

Jumped the fuel pump ballast resistor?

djgrayxj

Note from DJ
I was thinking about the CPS also.
Question to OP tbrunke
When you’re Power Latch Relay starts clicking is the engine running?

tbrunke

Yes it does restart right away.

tbrunke

I have not yet tested the CPS, it is new, but it is an electrical part so may very well be bad. Will test today.

Please explain what you mean by jumping the fuel ballast resistor.

BTW thanks for the great Renix tips you have posted I have implemented many of them.

tbrunke

It will click when it begins to stall out while the engine is running. Sometimes the Jeep dies, sometimes it doesn't, whereas the relay will continue to click.

67 GMC

I had something like this on my '87 but you have done lots already so it might not be the same issue. Mine would just die and then not start (especially when warm). It was the dipstick ground that looked good but wasn't. I took the bolt off, wire wheeled it clean and also wire wheeled the block where it connected. Then put a new ground cable to -ve on battery. Fixed my problem. I've never had any issues with the PL relay. What about your ignition module? Cruiser's by-line is "always refresh connectors" so maybe pull off the connectors and clean them up too around the ignition area. Did you try putting back your old parts to see if they problem is still there? If you put in the old MAP sensor and it still dies, then you are pretty sure you've got two good MAP sensors!!

cruiser54

Do posts 1 through 5 before anything else.