Ryan -

Thanks for the detailed description and pictures. My butterfly valve shaft has significant movement. Looks like this will be one of the next projects. I may need to pick your brain before I start this project. Hopefully it can survive for a couple more months.

If it has a lot of play I believe you can take the vac line off the actuator and plug it, it may decrease the chance of failure, others can chime in on this hopefully.

Some one also took the butterfly valves out and plugged the holes that were left in the manifold with bronze inserts that they made up.

While this is definitely a cheaper way to address the problem, what you're essentially doing is disabling a system that Mitsubishi's engineers spent a lot of time and effort to develop in the process of making this engine one of the most powerful engines for its size that was available in the mid-90's. Auto manufacturers don't typically add complicated systems to vehicles unless they make a significant contribution to the vehicle - a factory rep for Nissan once told me "Parts that we can leave off of a vehicle don't cost anything to manufacture or install, and they never come back for warranty repairs" If Mitsubishi didn't think the system's benefit outweighed it's cost, it wouldn't be on the engine in the first place.

Some people have removed the variable intake system butterflys and plugged the holes and have said that they don't notice a difference in performance afterwards. I will guarantee that before and after dyno runs would confirm a loss of torque at lower rpms due to the loss of the longer tuned intake runners. There's a reason that virtually every modern 4 cylinder engine on the market today has the same variable intake system technology - the longer, tuned runners increase the engine's low end torque.

I think that it might be worthwhile to check with some local machine shops to see if someone could fabricate some replacement bushings for your lower manifold - I don't think it would be too difficult to disassemble the butterfly and shaft assembly and install some brass bushings, and it could easily be a lot cheaper than a replacement lower manifold - you would just have to deal with the additional downtime. I've kept my old lower manifold after I replaced it for exactly that reason, I just haven't had the time or the need to pursue it.

Thanks Ryan. I agree. It's just too bad these motors cost so much to fix properly. <img src="/forums/images/graemlins/rolleyes.gif" alt="" />

I am not arguing with you, I replaced my lower plenum to fix the issue.

But if you can't afford the parts, and you have to use the vehicle, it may be better option than having the engineers hard work fall into your combustion chamber.

Tuned intake runners, and messed up cylinders with bad compression, does not a good combo make. <img src="/forums/images/graemlins/shiner.gif" alt="" />

Doug -

I appreciate your thoughts. I'm going to pull the vacuum line until I have time to replace it.

That won't help. It's the flutter from the loose bushing that causes the metal fatigue that causes the butterfly plate screws to break and let the plates dive into the combustion chamber. Hand wiggle the butterfly hsaft and see if the bushings are loose fit on the shaft. I'd be tempted to try getting some epoxy into the gap and tightening it up for a temp fix...

Good to know, it was definetly suggested before as a possible fix. Disconnecting the actuator and removing the play with some j b weld, like you suggest may be the best short term solution. Or do you think the epoxy would allow it to stay operational?

No it will not fix it ...Not to be a jerk ...But your playing with fire and your going to loose and get burned...The ONLY way this can be fixed is to pull the top end off ,,Sorry ... I've fixed a dozen of them over the years ..Its easy for a good machinst to do in know time...Of all the motors on the planet this is one of them that you dont want to have it frag on you .. Cost and finding the parts are just two hard ..You have two things that are going to bite you in the back side..The belt maybe bad and the butterflys ..And you know Doug what will happen if ether one of these lets loose...You have been around here sents 01... I would trade you one of my fixed manifolds for your bad one so you would have less down time ..But there out on loan for a motor mock up ..(TT motor in a airplane,,lol..).. Maybe someone can loan you one to get fix so you have less down time ..??

Sorry on the rant and all ..I'll shut up now ... Its just hard do to my job to deal with the "mind set" some times ..Sorry.. <img src="/forums/images/graemlins/frown.gif" alt="" />..

David

Hazardous Toys inc

When I first put my 95SR on the road the shaft bushings were in terrible condition. Clattered horribly. I ran it a few years with the hose unplugged with no issues. With the valves in the open position there is essentially no pressure pulses acting on the valves.
My second SR came with a new lower intake so that was swapped in. If there is an improvement in low end power or economy I do not detect it.

I do have experience with the electrically activated intakes on the 3.0 12V and the 3.0 DOHC in Diamantes & 3000GTs. Both these engine gain a great amount of power with the system disabled. With the 12V engine the valves open around 3K, the issue is the intake is to restrictive from 2500 up till the intake opens. The car could not torque up a hill at all, always needed to downshift to get over 3000 revs to climb. Once I disabled the intake valves the car would climb hills in top gear and I saw a 2MPG improvement.
Then I started working with the 3.0 DOHC, That intake opens at 4500 RPM, what a joke. The engine was just flat till the valves open then it screamed. I very soon disabled the valves and the engine pulls full strong from 3K and again a major increase in mileage. 27- 28 MPG average in a Diamante wagon driving in hilly country.
I expect if one could program in a lower opening RPM then there maybe value to this system.
Keep in mind these intake valves could well be implemented as a torque reduction system intending to reduce driveline loads as we have seen in the later Starion manual cars. In the Starion they use the dual diaphragm wastegate to reduce boost till upper RPM just to ease up on the gearbox.
In my Montero I have eliminated the little vacuum canister on the intake valves. What this allows is the valves to open sooner when the manifold pressure drops under load. I do need to do some testing to see in this engine is better with or without the valves.