HI everyone! We've had a 1990 Montero RS in the family since my grandpa bought it off the lot, and it's now become my responsibility to take care of it. The maintenance on it was neglected for a long time before I got it, so there's a lot wrong with it. This is only on one or two of the symptoms, but I have a lot of information so this may be sort of a long post (sorry).

There's one main issue that makes me afraid of taking it on long trips: when the throttle is open (accelerating or maintaining speed), the car will intermittently lose all power as if it were out of gas (it's like a lurching). It's been doing this since before I owned it, but it got so bad recently that I couldn't make it home from the grocery store. I'll list my process and failed attempts at fixing it here:

In my quest to diagnose this, I grabbed a DMM and pulled the fault codes. Here's the list:

• 11 - O2 Sensor
• 12 - Airflow sensor
• 13 - Intake Air Temperature sensor
• 14 - Throttle Position Sensor
• 25 - Barometric Pressure Sensor
• 41 - Fuel Injector Fault

So, basically everything you could think of. At first I thought it may be a wiring issue since a lot of these sensors share a ground, but after testing, every sensor was getting perfect power and ground.

I figured all of these sensors were 30+ years old so I might as well replace them anyway, and the first to get replaced was the TPS. I ordered a new one from Rock Auto, and began testing it against my old one when it arrived. I unfortunately don't have backprobes, but I ended up begin able to measure it anyway: when the internals were turned by hand (sensor dismounted), the old one read 0V - 5V as expected. Strangely, the new one read ~1.2V - ~4.5V. My mechanic friend said to just toss it in anyway and see how it is, so that's what I ended up doing.

After letting it idle for a few minutes, it actually ran better than it has in the last 5 years. The idle was much smoother and the acceleration felt normal. However, a few days later, all of the previous symptoms got 1000x worse (video with my foot on the throttle here). I tried adjusting the TPS to see if that was the issue, but I just couldn't get the new one to work, so I threw the old one back in just to make it home.

I'm good with a wrench, but I've always been terrible at actually diagnosing problems, especially on this car for some reason. So, I figured I'd turn to the people who are familiar with it. Has anyone experienced issues like these before or know what's going on? What went wrong (or what am I doing wrong, more likely)? Thanks, and sorry for the long post. I just want to provide as much information as possible.

 

Check your ECM. Open it up and look for melted capacitors. They are not to go bad after some time especially with the drastic temperature changes in NM