My 91 Montero's engine just quits....whether it is running in the driveway or as I am travelling down the road. All the power cuts out (dashboard lights, radio, etc). When I turn the key, it starts right back up. I took it to the shop where it was hooked to a diagnostic machine....at first, it ready 'normal', then it gave static results. The conclusion was 'computer is needed'. I drove home in the vehicle without the repair ($2200). At home, it stopped running again....when I opened the hood, it started when I turned the key....when I closed the hood as the engine was running, the engine stopped. Ideas?

 

I'm no expert at this but I've been around montero's long enough to maybe help some...

Why do you, or they (your mechanics) think its the ECU? Normally your engine won't start at all if its the ECU. Were there any codes shown when they tested the ECU or did it actually give a fault not showing any codes or voltage? You can easily test it yourself with an analog multimeter set to measure voltage. Do you have access to one & know how to use it?
If so, here's the proceedure for doing that...


Have you inspected the ECU? You can easily remove it and check for blown capacitors (most common problem). If they're blown but everything else is in tact you can simply replace them. If however your ECU board is damaged you will need to have that repaired.

Another common running problem I've seen is the coil, power transistor, coil wire, etc can each have an intermittent fault (open or short) creating a tough to find problem.

 

A bad ECU will prevent the engine from running, but all other components of your vehicle (radio, dashboard lights) should still function as normal. With that being said, it sounds like you might have a problems with the ignition switch (which sends power to the listed components). Have you tried jiggling it when the engine is running to see if you can promote a stall?

Joel, CA