Firstly, I want to introduce myself, HI!
Second, history...

This past year both myself and my better half have purchased cars... both crazy rear-wheel drive, sports cars... (E46 M3 and Solstice GXP if your interested)...
They are AWESOME... except when it snows. So, instead of buying a good set of winter tires for my Bimmer... I decided... hey, we should buy a winter beater, plus I can work it up into a fun summer truck for camping.

So, locally searching we found a '89 Montero SWB V6. I dig the body style, One of my first girlfriends had a Raider that was fun!
Anyways, It was in decent shape externally, The engine had some 280k miles, I expected it to be in worse shape engine wise.

The kid we bought it from had obviously done some restoration work on it. Coolant lines replaced, vacuum lines replaced, steering linkage and suspension joints lubed etc. New plug wires and distributor cap (I haven't checked the rotor).

During the test drive, it didn't have any steering wander, the brakes felt good, suspension was stiff.
I did notice a bit of power loss, though the clutch grabbed good and didn't slip. I didn't ever really get it up over 45 because it wasn't registered.

On the drive home, I realized that 55mph was a chore and 65, is basically undoable without dead flat road (hopefully a small downhill). 75? Never gonna happen.

After checking the fuel delivery, I noticed the filter was OOOOLD. So I replaced it with a new one. The old one was dripping dirt, rust etc, out of the inlet side, luckily the filtered side was still mostly clean. After replacing it, it starts great! Idles fine, and "seems" to have more grunt at the 1000-2500 rpm area. Though high speed is still a dream. 45mph is it's comfort zone.
It seems like after about 2500 RPM the power just drops.

I next suspected a crappy cat, so I yanked the o2 sensor, which basically made it run even WORSE lol, plugged it back in and unbolted the cat from the engine side exhaust, now it's LOUD but still has power loss above 2500k.
Also, I was backfiring a bit today on my drive, randomly, but it was there.

So my hope is that someone can guide me in a better direction.
My next thought is that it can't get enough fuel for the higher RPMS to make power (Failing Pump? Injectors? Regulator?)
Or, the O2 Sensor is bad.
Today I'll likely be testing the TPS to see what voltage it's putting out. It looks original (yellow beige plastic). Though it doesn't really surge in RPM, it stays flat and moves with my foot.

(Also, I considered yanking the ECM and trying to re-cap it. THough I can't find the damn thing)

Anybody have any ideas on my next course of action?

I REALLY want to love this truck, but as of right now... the damn thing is pissing me off and the drivers behind me.

Thanks in advance,
and nice to meet you all!

-Mike

(In case it doesn't say below, it's a '89 SWB Montero V6 FI. 5 Speed. )

Perhaps a clogged cat? Perhaps timing? Perhaps fuel delivery?

Welcome to the Wire. <img src="/forums/images/graemlins/kewl.gif" alt="" />

Welcome to the Wire!

Sounds like you're off to a good start. I'd check the easy stuff first - make sure all your ignition components are in good shape and that the ignition timing is set properly. If the fuel filter is as bad as you stated then your injectors are likely gummed up and not performing as well as they should be. Running some Techron injector cleaner through the gas tank would be a good idea, and it might make sense to take it into a shop that can perform an injector flush on the vehicle. Testing your fuel pressure would help to make sure that your fuel pump is working properly. Check for anything obvious like missing or broken vacuum lines or any other potential vacuum leaks in the air intake. If you still have issues after all that, check back here for more help.

Welcome to the Wire!

First things first, go to mitsubishilinks.com and get the FSM for your truck. And don't forget to leave a little love on PayPal for the site guy, he did a lot to get that up there. Don't give up, 65 shouldn't be a problem. I do it all the time with 35's

Thanks guys!

Well I think I'm going to bolt the cat back up.
There isn't emissions where I have it registered, so I'll probably jam a rod through it and pseudo straight pipe it.

Connected or not the difference isn't noticeable.

I also figure it has to be fuel delivery. As nasty as the filter was I figure the pump strainer may be clogged. I bought a new pump $20 on amazon (an airtex even). So I'll likely change the thing this weekend. Gotta love that access panel in the rear deck.

I have access to a reflow bench as well, so I may yank and rebuild the injectors.

Also I think it could be mechanical timing. I'll probably do a whole tune up. I am going to dl the fsm and kick the up loader some beer money.

I'll keep it updated in case any of it is archive worthy.. lol


-mike

Based on past experiences (non-montero) this sounds like fuel delivery or valve adjustment (cam lobe wear, timing, valve lash, etc).

You're doing the right thing baselining the truck, just count on doing the plugs as well...

Cheers,
m.

One way to do an 89 V6