All of the sudden (last December) my Montero went from running fine to very rough like someone flipped a switch. Barely made it into my garage, then a gas pool formed under the tail pipe. I tried starting it again and it used a half gallon of gas in 10 seconds (I measured by how much I could refil it). Pool of gas all along the tailpipe and the engine oil had gas all in it so I had to change it. Then when I reconnected the battery it clicks on and off, the siren sounds if I plug back in the connector. The door locks rapidly lock and unlock and the dash lights flicker. I've replaced a ton of stuff, MAF sensor, MAP sensor, IAC valve, EGR valve, 3 coil packs on the engine, EGR electric solenoid, replaced the alternator, nothing has even the slightest impact on the issue. Even replaced the ECU. I have a '98 factory wiring manual and from what I can tell there's nothing that interfaces all the things I'm seeing other than the ECU which I've replaced. Anyone have any idea what's going on? I'm about ready to part it out.

 

Did you check your fuel injectors? Sounds like one or more of them might be stuck open.

 

hi
i once had something like that on a isuzu trooper 3.5
with the gas coming out of the tail pipe and a lot of white smoke
it turned out that one of the injectors got grounded somewhere along the wiring harness and it stayed open.
but there was no issue of gas mixing with engine oil
aharon

 

If un-metered/excessive amount of gasoline is sprayed into the cylinder(s), it can wash down the cylinder walls past the rings and get mixed with engine oil. This is very bad, because 1. it removes oil from cylinder walls, resulting in excessive friction/wear. and 2. it dilutes oil and thus reduces its lubricating properties throughout the engine. I would not drive the vehicle until this condition is fixed. Otherwise you risk completely blowing up your engine.

 

Yes, replaced with 6 new injectors and replaced the connectors + checked for continuity with multimeter. I was thinking the same thing. I also saw that from the '98 wiring diagram that the ground is common among many of the solenoids and sensors and maybe one had shorted out and was bringing up ground and causing the injectors to open. But disconnecting basically all of them except the ones needed to run the engine, it still does the same thing. I'm thinking more and more its the alarm system. I notice from searches it has been said its an aftermarket (viper) security system. Not sure if the 2000 is still the same system. This one is interfaced with the dome light (which have never worked), blinkers, the siren, starter interrupt, sensor (located on the steering), and a switch that apparently is broke and someone had a guillutine electrical connector joining the two button pins. I tried disconnetcing everything but it does not send power to the starter when I turn the ignition switch to start. I've read to remove it entirely but I'm having difficulty seeing where all the wiring is. I think that's my next step to reconnect the original starter wire to the ignition and remove the "mitsubishi security system" entirely

 

This was my fear as well. I had a snowmobile that the float bowl needle valve failed and it dumped too much gas in the cylinder and it scored it all up due to washdown. I'm sure there's been some damage just hoping its mostly still what it was.

 

I think this is the other possiblity. I haven't found a short in the wiring so far so far but i'll have to check everything if this security system removal doesn't help. I think its that because also I forgot to mention as soon as I plug in the battery there's a tiny beeping on and off under the dash and the locks click on and off rapidly as well as the dashboard lights dimming/flickering.

 

I'd think security system would cut off power to injectors, not turn it on full bore wide open. However, I don't know how your truck is wired, so perhaps you are right, or this is a "side effect" of security system malfunctioning. I hope you can figure it out. Once you do, please update us her.

 

From my searches, I had the impression the security system was an aftermarket one and hack job'ed into place by the dealers upon arrival. But my 2000 Montero (regular not sport) looks to have the viper module but the wiring looks factory after that, like they integrated the system into the wiring harness. I want to remove it and just have the ignition wire skip going through the system (at least that's my theory) but this 2000 model's wiring under the drivers knee panel doesn't look like what was described in threads I read. I see factory manuals are available but for ~$175-200 on ebay. yikes. I'll see if my meager brain can figure it out with a multimeter. I'll report back eventually if and when I figure it out

 

Been lurking but didn't have anything to suggest that wasn't already covered until now. I know you have a Montero and not a sport, but I got to thinking that the sport has what's called a "fuel consumption unit" in the passenger side kick panel, Maybe the regular Monty has one as well? Also, I know you said you checked a common ground point in your original post but have you checked the grounding point(s) for the ECU? A bad ground for the ECU can cause all sorts of weird glitches.