Possible vacuum leak.

[fitbikeco]

Alright i wasnt to sure how to post this topic or even how to search it. This is my first post so im hoping i dont get called a retard too many times. so about 2 months ago something im my drivetrain messed up. I didnt have the money right then to fix it so i let it sit in my driveway till the time being. so i get it towed to a buddies house . and usually when i would start it up especially if it was cold it was alittle stubborn to run. wich from what i hear isnt uncommon apperently. but now as soon as you start it at an idle the boost guage is showing like 7-10lbs and it sputters real bad like it wants to stall out. ive never had any problems with this before it sat. but a few months back it stalled out on me at a light and i all of a sudden could hear a really loud vacuum leak

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when i got the car all that covered that hole was a peice of electric tape and thats where the air was coming in.. i just want to know what is supposed to go there...is it a vacuum line. and if so where does it go to or come from....any help would be great..

 

[kenamond]

Alright i wasnt to sure how to post this topic or even how to search it. This is my first post so im hoping i dont get called a retard too many times. so about 2 months ago something im my drivetrain messed up. I didnt have the money right then to fix it so i let it sit in my driveway till the time being. so i get it towed to a buddies house . and usually when i would start it up especially if it was cold it was alittle stubborn to run. wich from what i hear isnt uncommon apperently. but now as soon as you start it at an idle the boost guage is showing like 7-10lbs and it sputters real bad like it wants to stall out. ive never had any problems with this before it sat. but a few months back it stalled out on me at a light and i all of a sudden could hear a really loud vacuum leak

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when i got the car all that covered that hole was a peice of electric tape and thats where the air was coming in.. i just want to know what is supposed to go there...is it a vacuum line. and if so where does it go to or come from....any help would be great..

That's where the BISS (base idle set screw) is supposed to go. If you look in the hole, you should see the head of the screw. If there's no screw, that's a BIG vaccuum leak. For more info about this, check here (this site is VERY useful, BTW) and also do a search on this forum for "BISS". If the screw is in there, but it's sucking air at idle around the screw, the o-ring around the screw is leaking and needs to be replaced (do a search and you'll find a ton of info on this; it's a common boost leak). If the screw is there, try putting your thumb over it with the car idling and see if the idle improves. I'm no expert on BISS, so it may be that the ECU has already tried to compensate via other idle controls, and covering the opening with your thumb may not fix it.

That's all I know about that. Good luck!

 

[fitbikeco]

well i know for a fact there is no screw in there. like i said when i got it there was just a peice of tape over it. then one day it just started sucking air through it. I saw threads in there when i looked i just wasnt sure what was supposed to go in there.

 

[kenamond]

well i know for a fact there is no screw in there. like i said when i got it there was just a peice of tape over it. then one day it just started sucking air through it. I saw threads in there when i looked i just wasnt sure what was supposed to go in there.

The BISS lets air bypass the throttle plate. If there's no screw, there is a hole connecting the intake manifold to the atmosphere. I'm not sure how large the passage is, but it's going to be sucking a lot of unmetered air at idle (when the intake manifold sees vaccuum) and leaking a lot of metered air under boost (when the intake manifold sees pressure). You'll be running lean at idle and rich while boosting due to the metered air issue (the MAS measures air just after the air filter, and your leak is after that measurement, so the ECU is being told the wrong amount of air entering the engine, so the fuel it injects will not be the correct amount).

How does it idle?

I'm wondering if the BISS got loose and then popped out under boost or just rattled out.

So you need to buy a new BISS and new o-ring. You need it.

EDIT: Check out that site I mentioned in my first post. It tells you a bit more (some useful info about how to adjust the BISS once you get a new one). You'll probably have to search the forum to find out a full-blown procedure for proper BISS adjustment.

 

[fitbikeco]

well if its cold out like it is now 30 or below starting it is very ruff. it will start right up. but the boost guage will read like 10ps and it sounds like its gonna stall out but it dosnt...and when it was wamer it would do that but when the car would warm out the idle would even out and it was fine. I put a vacuum cap on it a while ago but it wasnt a very good seal and you could still hear it leaking. and also i just now noticed to that when i turn the key on. not start it. i can hear a clicking from my coil pack. im not sure if that would have anything to do with it. but the coil pack looks brand new the motor has about 10,000 miles on a rebuild and they replaced alot of things in the process

 

[kenamond]

well if its cold out like it is now 30 or below starting it is very ruff. it will start right up. but the boost guage will read like 10ps and it sounds like its gonna stall out but it dosnt...and when it was wamer it would do that but when the car would warm out the idle would even out and it was fine. I put a vacuum cap on it a while ago but it wasnt a very good seal and you could still hear it leaking. and also i just now noticed to that when i turn the key on. not start it. i can hear a clicking from my coil pack. im not sure if that would have anything to do with it. but the coil pack looks brand new the motor has about 10,000 miles on a rebuild and they replaced alot of things in the process

Replace the BISS. This is from www.vfaq.com - another great DSM site.

As for the clicking, it may just be the fuel pump. It pressurizes the fuel system when the key is moved to the "on" (not start) position. I can't think of what else might be heard in that situation, but that doesn't mean it can't be something else . If you pull the rear seat cushion off and have someone put their ear to the fuel pump cover (grey rectangular metal cover with 4 screws and a wiring harness coming in from the passenger side), they should be able to hear if the sound is coming from there. Some of the fuel pump upgrades are louder than the stocker, but I'm not sure if they click or not. I still have my stock FP (not for too much longer, though).

 

[fitbikeco]

yeah im definelty gonna get on the BISS screw for sure. im gonna go order one tommorow and when i get it in I will let you know the out come of it..thanks.

 

[kenamond]

If you scroll down to the bottom of that vfaq article, the mention the Mitsubishi part number for the BISS and mention that it's not called a BISS. They also give the o-ring part number.

Good luck!

 

[fitbikeco]

well i ordered the screw today. so it will be here either tommorow or monday. ill let you know how everything works out when i get it on.

 

[fitbikeco]

ok so i bought got the BISS yesterday and it didnt come with an o ring.. will any o ring from like lowes work or is it a certain one from the factory.

 

[dave99gst]

im sure any o-ring would be close enough, the problem is you do not have anythign to compair to.
Its prob a metric sized o-ring from the factory and lowes carrys english. (just a guess)

 

[kenamond]

ok so i bought got the BISS yesterday and it didnt come with an o ring.. will any o ring from like lowes work or is it a certain one from the factory.

Go to that vfaq link I posted in post #6 of this thread. It mentions the generic o-ring size, I believe. They're so damned cheap, I'd just take the BISS to the hardware store and get a handful of sizes that look like they could work. If it seals the BISS (verified via a boost leak test and spray bottle of soapy water), you should be good. The only concern is that it might degrade more quickly than a "special BISS o-ring" if such a thing exists. Heat turns some of the rubber parts into hard plastic over time which doesn't seal as well (like injector insulators) leading to future boost leaks.

EDIT: From the vfaq site: "#5 O-ring (3/8x1/4x1/16, available at most hardware stores)"

 

[Dream On]

Same thing happened to me. The car ran like like crap and stalled out and I was really scared at first until I saw the gaping hole.