Need help ASAP!!

[PapaBear]

Guys, I need some help, I'm stumped. I have a 1990 2.4 MM, 5 speed, with 335,000 miles. She has been a great truck, and finally bit the bullet. I was headed to school one day (20 mile drive) and she started getting sluggish. Didn't want to make any power. I got to school, and realized it was using gas like crazy. I had to make it home, so i drove it. About 3/4 of the way, it got worse, couldn't make it over 40 MPH on the interstate, and slowly got worse, leaving me on the side of the highway. It seemed like a cat was clogged or something, so I went back to the truck and removed the exhaust. Still same issue, so I towed it home.

I changed fuel filter to no avail. Now I'm stuck. I pulled the MAF and it appears to be new. I did read that it is not cleanable, and they are super expensive. There's my problem. I don't want to spend $150+ on a MAF and it not be the issue, seeing as though it's an electrical part and not returnable.

Any ideas?

Thanks in advance.

[DroppedMitsu]

Does the compression seem good, look at the spark plug tips what color are they? Might need a new fuel filter as it could be clogged. Any codes being thrown(is your check engine light on)?

[camoit]

If it has a timing belt it could be coming apart and jumping time.

[PapaBear]

Does the compression seem good, look at the spark plug tips what color are they? Might need a new fuel filter as it could be clogged. Any codes being thrown(is your check engine light on)?

Thanks guys. That's the thing, NO CODE thrown. As stated in OP, I did change fuel filter. I have not checked compression, only because I don't see that as being an issue. The plugs look like it's been running rich, which it surely has as it was DRINKING fuel the day it quit.

If it has a timing belt it could be coming apart and jumping time.

I debated this as well, wondering if the timing could change enough by jumping time to make it run bad. But it happened very gradually, not something instantaneous like jumping a tooth or two on a gear, so I have not inspected this either.

[camoit]

It could be an injector is stuck open or broke the tip off. Or the fuel pressure regulator is over pressurizing the system.

[PapaBear]

Any ideas on testing these theories? Or where to start? Fuel pump? Pressure regulator?

The goal is to fix this thing without just throwing parts at it. I'm a broke college kid at this point, and having to drive my V8 is killing me at 12MPG......

[camoit]

look in the manual section > over 216 manuals > montero it covers your truck.
This will give you a flow chart to look through and how to test things. FI in not my department in these trucks. First gen is.

[Andy 2]

Is your air filter clean?

[pennyman1]

look for air intake cleaner - its made to clean MAFs without damage - your o2 sensor may have failed and thrown it into a limp home mode, or the EGR is jammed wide open strangling the motor

[pennyman1]

look for air intake cleaner - its made to clean MAFs without damage - your o2 sensor may have failed and thrown it into a limp home mode, or the EGR is jammed wide open strangling the motor. There is a slight possibility that the caps died in your computer, causing it to lose signals to the injectors.

[BradMph]

335k miles. oh my gawd that is 13.4 times around our planet, Thats all the way to the moon and half way back, thats over 100 cross country US road trips, thats 49.3 times around the moon, thats 25.8 times around Mars and or about 335,000 times to the Grocery store. If I compare those miles to my truck of 270,000 miles, I have just broken in my motor, lol. That is some incredible miles to be on a little truck. Hope you get her fixed.