03 montero sport starts but dies in 20 minutes
 

I have an 03 montero sport. I have spent over $2000.00 trying to fix this problem. There are more new parts under the hood than old. I replaced the radiator, clutch fan, timing belt, adjuster, pulley, crank and cam sensors, and even the ecu. Starts fine, but shuts off after 20 minutes. I took it to the dealer, and was told the Montero doesn't like aftermarket parts. The mechanic ran an oscilloscope test and it showed the cam sensor failing at 20 minute mark. Was told to replace the cam sensor with a factory sensor. I did that. Same exact problem. I am ready to scream!! Any ideas???? I have invested way too much money to walk away, help!!!!

Does it throw any codes? Do you have an aftermarket anti-theft system by any chance?

same codes as when the process started. Camshaft sensor, crankshaft sensor. Runs with camshaft sensor disconnected, but poorly. Shuts off immediately if you unplug crankshaft sensor

Factory alarm system

Sounds like you have an issue with one or both of the sensors or with wiring going to them. You need to test to see if you have proper reference voltage going to them and if you are getting signal out. Again - it is possible to have a bad sensor, OR some issue with the wiring (even a bad connector).
The fact that vehicle runs, but as you say - poorly, indicates that it runs in the Open Loop or in a some safety limp mode.

I have now ordered a factory crankshaft sensor. The camshaft sensor was replaced with oem sensor, now replacing the crankshaft sensor. I hope this works. My mechanic is really getting tired of seeing this truck.

Resolved!!!!
 

Finally! After $3000 in repair cost my car is running again. Never ever use aftermarket parts on these cars!!!!!!! Factory electronics only, or you will be very sorry!!

Great news!

What was the faulty aftermarket part, and where have you bought it?