TOPIC: 1990 Mitsubishi Montero, 3L, Costa Rica

This TB had 2 internal air pathways (whats the right word for such things?) that I cut into. It wasn’t my plan, but I couldn’t have done the mod otherwise as they’re close to the center of the groove and fairly shallow. I didn’t (and still don’t) know what they’re for, but I noticed that on the part of the intake manifold across from where they exit the face of the TB, there’s no continuation. In other words, they seem to dead end. I’m hoping they were built in to the TB design so it could be used on multiple vehicles and that they’re not used on this one. I’ve attached pictures so the rest of you can make sense of what I’m saying.

Also these internal pathways I’m talking about seem to connect to the two pathways that end in the letters A and E which can be seen on the pictures. They also don’t seem to be in use.

Can anyone tell me what those pathways I cut into are for? And am I right that they’re not being used for anything? (except to scare me after I cut into them)

Another thing about this mod is that the “Maintenance Required” light is on. It’s the first one I’ve ever seen. The vehicle has a separate Check Engine light and it’s not on, so they’re not the same thing. From reading online I get the impression the “Maintenance Required” light is not indicating a problem, but came on automatically at a certain mileage interval to advise the owner to check the timing belt or something similar.

The client noticed an increase in torque (is that what it is?), by noting that he can now reach 100 km/hr. at 2,500 rpm’s instead of 3,000. However, he had good power beforehand and came to me looking only for increased mileage, which at this point has only increased slightly.

I capped the PCV port on the intake manifold, but haven’t checked for vacuum leaks yet and will do so next week.Apart from that though, given that it’s a 1990 vehicle, I’m wondering if the O2 sensor might be a problem.

Any suggestions on how to tell if the O2 sensors are sluggish/dying/whatever – without using a scantool?

It's also idling a bit high (1200-1300), and he says it's difficult getting into first and second gear. For the idle, maybe I have to move the groove, but it settles down quickly to 900, so I'm not sure if it's warranted.

Cheers,
Jonathan

Hi Jonathan,

Looking at the pic's, I don't see the 'A' & 'E' ports being used for anything.

The 'P' port... what does that hose do that is connected to it.

Also, on the TB the large openings at what would be the bottom side of the TB, is there an Idle Air Control on this and if so did you do anything to reduce the air flow through it?

Nice Groove

Karl Fortner
Tacoma, Washington

A couple quick corrections to my post.

The internal air pathways I cut into weren't connected to the other ones labelled A and E, but to those labelled E and P. And I think the P line is the purge pathway for Evap. Emissions. So it is an active line, but I'm hoping it purges through the small hole I labelled on one of the pictures, and that since the part I cut was past that hole, that having cut into that pathway makes no difference. If anyone knows about this please let me know.

Also, the part I labelled thin spot is where I cut through the TB and then patched.

Hi Karl,

I posted my second message before seeing yours, but I guess I partially answered your question about the hose that connects to the P port. I think it's the Evap. Emissions purge line, through which the fuel vapors get in to the TB. I think they come in through what I called "small hole" in one picture, when the throttle plate is open enough that vacuum gets to that small hole and sucks the vapors through it.

As for Idle air. I think it has it. In the pre-mod pic that whole dark smile looking part above the word Montero seems to be idle air. (though I didn't actually verify it when I did the mod) I’ve included 2 new pics taken from the breather side of the TB to illustrate. One points to what I think is the IAC, and the other is the same view but from further out.

So… assuming it has IAC, the groove was cut on the opposite side of the throttle plate (the top ½ in the IAC pic) so the idle air isn’t being dumped in front of the groove. Do you still recommend reducing the idle air flow? If so, why? Is it a preventative measure based on the idea that the IAC is a vacuum leak, and thus reducing the size will curtail the leak?

As for "nice groove", thanks, but man I really panicked once I cut into those 2 lines. After I concluded that it would probably be okay to patch them, the patch didn't hold. By the end of the day I'd grooved that TB 3 or 4 times.

Hi Jonathan,

"Do you still recommend reducing the idle air flow? If so, why? Is it a preventative measure based on the idea that the IAC is a vacuum leak, and thus reducing the size will curtail the leak?"

Yes, you definitely want to reduce the IAC opening. Even though the ECU monitors the air flow, you want as much of the air as possible to be going over the Groove and not bypassing it. By restricting the air flow via the IAC it increases the manifold vacuum and the air goes through the TB by way of the Groove.

You can close off most of the opening on the bottom side of the TB and put a 1/8" slot as a pathway for the idle air.

I think you'll find that it will idle down better as well.

I find that the JB Qwik works well for some things but when I have the opportunity and the time I'll use the JB Weld. Much longer cure time but better to work with for re-grooves, etc.

Later

Karl Fortner
Tacoma, Washington

Hold on a minute here, Guys.

As I look at the throttle and the groove location, was it placed correctly in the first place? It appears to be on the wrong side.


Or, am I just looking at it wrong?

The purge line may be attached to the intake air stream before the throttle plate. I have heard reports that this can be done without resulting in an error code.

So, that hole may be plugged and re-grooved if you like. Let us know how it goes!

Ron

Ya know... I looked at it and looked at the throttle cable assembly...

Ron, you are correct.

jonathan... you've gotta move yer groove to the other side

You want the groove underneath the side of the throttle plate that opens towards the intake manifold. That way, as the Plate opens it is engaging the groove.

and you want to close up the IAC openings and route the IAC path up one side towards the axle of the plate.

Silly little things that don't pop out at you

Karl Fortner
Tacoma, Washington

Ron and Karl,

Enormous thanks to you both.

I thought the throttle plate on this one opened at the top and not the bottom like usual, so I cut the groove on the top. But…looking at my own photos I agree with you guys. Maybe I was looking from the breather side when I thought it opened at the top.

I assume I should refill the groove on the wrong side, but would leaving it unfilled be detrimental?

Once the old groove is filled or ignored, I’ll get on with the idle air reduction and reroute. It looks like l can fill in the rest of that chamber to the left of the IAC air entry, and the notch that’s cut out of the TB barrel on the right (see pic). Then I’ll regroove it, so if it punches through on the right I’ll be able to thicken that wall before making my new idle air path. Then I’ll carve a channel through the little chunk on the right that I’ve called reroute, so the air enters the chamber to the right of the axle.

That chamber at present is another idle air entry. It has an adjustable screw (I labelled it 1 in the pic) that can be opened up to let air in, which then exits at 2. Probably that screw seals well when it’s completely closed, but I’m thinking maybe I should seal the area where it lets air in (item 2) with epoxy just in case. Then if I have to increase his idle, I could do it by tightening the throttle cable. Any thoughts on that?

This thing has a thin metal gasket between the TB and intake manifold. Do thin metal gaskets seal well? I almost feel I should add something softer to it like some RTV to get a better seal.

That’s an interesting idea with that purge hole. I think all I would have to do is plug it, and then redrill it on the other side of the throttle plate, (making sure it ties in to the purge pathway or or whatever it’s called).

Jonathan

you may not need to fill top as I have cut both on certain models and gained alittle more mpg its trial and error. good luck just keep doing the mods Im planning on being down there hopefully this month Ill try to meet you Im meeting with the costa Rican govt as we have formed a coop down there.

Hey Dan,

Thanks, I may just leave the other groove, do the mod and see what happens.

I remember you were planning on coming down before. Glad to hear it sounds like everything is still moving forward with the CR gov't.

It would be great to meet. Keep me posted. Ron can give you my direct email and phone number if you don't already have that info.

Hey Ron,

Does throttle plate shaping increase mileage or only deliver more power? The throttle plate on this one is nice and thick.