I bought my '90 Montero in January this year. It had a lot of work done on it, and was running great. My neighbor, who had commissioned the restoration, decided to switch to an automatic vehicle and I jumped at the chance to buy it. Then in Feb, it started to randomly die. Usually it would do it a couple times until it got warmed up, but then got worse until it consistently dies within 45 seconds of starting.

I was on a trip in the Montero when it started dying consistently, and took it into a shop. They said that for some reason the fuel injectors were being shut down and so it was stalling. It was below freezing that week, and I told them when the ecu got warmed up, it usually ran OK and so they put a little heat on the ecu with a heat gun, and it did the trick, so I drove the 300 miles home without stopping (well once for gas). I don't know if this is significant or not. It's warmer now, and still stalls out.

I had some diagnostics done at another shop after I got home, and was told that my ecu was bad. So I got a reman unit from ebay. It fixed the stalling problem, but now when I start it up, it idles high (~1800) until it warms up, and then starts "loping" (bouncing between ~1500 & 1900 rpms) at idle. If I turn on the AC, it will drop down to a normal idle for a few minutes but then start revving up again. If id drive with the AC on, then it will either rev high or bounce between the 1200 & 1500 rpms when I stop.

I'm interested in getting more mechanical, but I'm a real novice. I've looked at the "Solving the 3.0l V6 Idle Problem" article, cleaned out the throttle body, replaced the isc motor, replaced the ignition control module, tried to check for vacuum leaks, checked for cracked wiring and bad connections, but haven't found any problems.

I don't know why the two different ecus would give two different behaviors. The one idles fine, but dies after 45 seconds, and the other runs, but then idles high and does the surging (revving, loping, not sure what to call it).

I sent the first ecu in to be remanufactured, and it was worked on and bench tested, and should be good. But the vehicle still dies. The second ecu is the "newer" kind that isn't supposed to have the capacitor problems the original had.

Any insight would be appreciated. Anybody seen this kind of thing before? Where should I look next?


Thanks.