idle/vacuum

[camas90gsx]

Once again i have an issue with my 1g.I installed a fmic and in the process i had to unhook the cruise box and slide it to a different part of the bay..When i first started it after the fmic install the idle was at 2100 so i turned it down.Then i went for a ride and it was awesome and boosted strong to 13 lbs.i drove it today and the idle was up again so i turned it as low as possible and the idle is jumping up and down and it will only boost to 7 lbs max.i also had noticed the vacuum line to the intake was unhooked but when i hooked it up the idle went higher.i loosened the bolts to the cables on the cruise box and maybe thats it?Im at the point where im pulling my hair out.Can someone please help me

 

[LiquidX]

You messed with the BISS and you shouldn't have touched it. Your idle increased either due to tension on the throttle cable or you have (most likely cause) a boost leak. Did you even do a boost leak test after installing the FMIC?

Find and fix ALL of your leaks, ground the diagnostic pin on the ECU, and adjust the BISS so your idle is at 750rpm.

 

[camas90gsx]

Also i had to shorten my intake pipe to fit in my new filter and in the process had to lengthen the pipe from the bov to the intake by 5 inches.Maybe that could have something to do with it?

I adjusted the idle to as low as it would go.Why would installing a fmic mess with the idle?The car was boosting great last night after the install.then today i shortened the intake tube and put a longer bov recirculation tube on and now its running different.but the idle was a little high last night when it was running great.idk?

 

[LiquidX]

That won't have anything to do with it. On a MAS system, all air is metered and is expected to make it to the motor. Changes in the volume affect many things dealing with the fuel trims and drive ability. Moving things around but retaining the same setup won't make a difference. The return line from the BOV could be 10ft long and it won't make a difference because it's still metered air and remaining in the system. Besides, the BOV is closed at idle so you would only have vacuum in that line being pre turbo.

High idle comes from excessive air bypassing the throttle plate either through a leak, improperly adjusted BISS, faulty ICS, throttle plate not being set properly, post throttle body vacuum leak.

Take my advice, do a boost leak test. Also take off the throttle body elbow and check to make sure the throttle plate isn't open at all (100% closed).

 

[LiquidX]

Also possibly you could have a blown intake gasket.

Which is a post TB leak which would be determined by a boost leak test as I said already...


With the stock ECU, it expects to see 750rpm idle. If it was high or low, there is an issue that needed to be figured out, adjusting blindly doesn't help. You are new to this and you will figure that out quickly.

 

[camas90gsx]

I just went out and my turbo and j pipe are both extremely hot, and I have no clue why that is either............

 

[Nasty Dream]

I think turbos get hot as #### and is normal.

 

[WeaselHack]

Besides, the BOV is closed at idle
so you would only have vacuum in that line being pre turbo.

How'd you get wiseman status again?

 

[WeaselHack]

Edit: OP call Lucas and let him take a look at it before you decide to sell it. He won't charge you much to look at it and he's just down the road from you.

As others have said you prob have a simple boost leak....Easy fix.

 

[LiquidX]

Yes, a BOV is closed at idle. If it isn't then it's not working properly. There is vacuum in the intake pipe due to the turbo...

 

[WeaselHack]

Yes, a BOV is closed at idle. If it isn't then it's not working properly. There is vacuum in the intake pipe due to the turbo...

A properly tuned BOV is open at idle. If it's NOT, you have a problem. Must I go take a video to proove it?

 

[LiquidX]

Yes, I can take a video of my TiAL at idle as well, it remains closed as it should.

 

[Nasty Dream]

i drove it today and the idle was up again so i turned it as low as possible and the idle is jumping up and down

I don't think this issue is related to your FMIC.

That description sounds like the idle speed controller.

It's going up and down, in some kind of loop? Definitely ISC.

Or even if it changes from day to day... They control the idle, and when they wear out they tend to just work sometimes, or work half way. That's because - if I remember correctly - it's controlled by electro-magnets. Magnets get weaker over time.

These things are bound to fail at some point, and are easy and cheap to replace. Well, I don't know if they are cheap, actually. It's just a small simple little mechanism.

You should totally replace that part before you part out your car. That's hilarious. As I said, its bound to fail eventually anyway so it can't hurt to replace it.

Mine got worse until it totally failed at like 65k original miles. On the other hand, I got mine from a part out of a car with 100k miles, and it still works 50k miles later. So they can/should last.

 

[WeaselHack]

Yes, I can take a video of my TiAL at idle as well, it remains closed as it should.

Then you've got too stiff a spring my firend.

 

[gofer]

Im not trying to start an argument in hear but if you've got the proper spring in your Tial Q bov then it should open at idle (vacuum), mine opens up so much you could drop nuts and bolts in the damn thing.

 

[LiquidX]

Corey, all my sources and the shops I've been to say otherwise.

 

[gofer]

Fair enough. Just letting ya know mine opens up entirely at idle too. I guess I never contacted Tial about the issue as it didn't make sense to me to have un-metered air entering a MAF setup but then again, its not a recirculated bov either so I gaffed it off. My vacuum is at 18 in/Hg and I have the unpainted (silver) spring inside, maybe I should contact Tial and see what it should do.

 

[Nasty Dream]

I have never had the car go one week without an issue.Thanks again for the help though guys,its much appreciated.

Even brand new cars can have issues.

"Never give up" - Brent Rau, 1,400 HP eclipse

Then i went for a ride and it was awesome

 

[WeaselHack]

OP: That's too bad. Just go double check everything, take your time...hopefully you have the long weekend but if you end up parting it out please PM me.

 

[Nasty Dream]

I swear, just try this:

MITSUBISHI ECLIPSE 4G63 IDLE SPEED AIR CONTROL ISC OEM on eBay!

$50

I didn't realize it's actually a pretty expensive part, new. Get a used one for $50, or hit a junkyard and get one for $5 or $10, if you can find a scrapyard with an engine still in the bay.

How to/diagnostic: http://dmtalon.v8eaters.com/ISC.html

You must be logged in to view this image or video.

You must be logged in to view this image or video.

2 screws and a wire connector and you're done. 5 minutes. If not, sell it back on ebay.

another source

Symptoms of failing ISC control motor include: idle surge, failure to idle up on cold start, idle oscillation with engine idle revving up & back between approximately 900 to 1500 rpm's at idle (which should be around 850 with engine at operating temperature) or an unresponsive high or low idle. The car should compensate and idle up when the a/c compressor, power steering or when fan is running. It's likely you'll need to replace this at some point in your Mitsubishi.

More images:

You must be logged in to view this image or video.

You must be logged in to view this image or video.

There are other symptoms too. Like mine, at it's worst, would idle between 800 and 4K RPM, it was mad annoying. (it would fluctuate up and down like someone was revving the engine)

Best of luck to you, whatever you decide to do.

 

[gusu]

Did you adjust the biss screw or not? Did you only loosen the cruise control section of the throttle cable or what did you do? If one vacuum line fell off assume more did as well, check them all.

I also can't get a PM to send to you. If you decide to actually sell or part out your car please let me know. You pretty much have the part list I'm working towards for my car. I hope it does not come to that though.



*edit* I reread everything. You can't skip steps on idle speed adjustment the way it was posted on vfaq or your ecu will compensate for the adjustment and moving screw does nothing.

It seems as though you have a boost leak. Try the soapy water trick and check all of your vacuum lines for leaks. Most likely while putting on your intake you had to struggle with all the bullshit in the way and ripped open your wastegates pressure source that goes to your boost controller. ALWAYS check for rips on it after reinstalling the intake. Both the 14b and the 16g puts it in the perfect position to get hung up on resulting in very easy rips.

 

[camas90gsx]

Ok so i had all night to sleep and chill out and went to start it and rpm went to 1900 and the check engine light is now on. To answer some questions i adjusted the cruise control screw because the cable came off the track and i had to correct it.And as far as the biss,i turned it a few times last night after all of this started.The screw had no tension one way or the other and i put it back to what it was i think?i decided to eliminate the ac when i installed the fmic as well.I was planning on eliminating the cruise as well.Right now the cruise box is just kinda hanging out next to the battery not mounted.Also the guy who helped me install the fmic adjusted the nut on the isc when the car was idling high after the fmic install he just told me.Im completely lost and have no idea where to start.Please help guys

 

[LiquidX]

"Nut on ISC", I think I know what you are referring to now. On the back side of the TB by the cable, there is a screw with the nut. Generally there is a prong on the top, that is the idle switch for 1g cars.

If that got turned in, your throttle plate is open now. Take off your TB elbow and look at the plate, if that screw it turned too far in, it will open the plate which you'll see. You'll need to back that screw out so the plate is fully closed. Only turn that screw in far enough so the switch on the bottom is depressed at 0% throttle.

This is a '90 TB and that screw is the one on the top left that you are talking about correct? The ICS on the '90 is the silver flattened can on the right side.

You must be logged in to view this image or video.

Fixing the screw position will get your idle back to a more normal RPM. You'll need to go through the procedure to set your BISS however since that got moved. The BISS just enlarges or closes an air passage that bypasses the throttle plate. The ICS is dependent on proper BISS location to maintain full range of adjust ability.

 

[Nasty Dream]

Cool, you got it working!

I try to see the bright side. You have adventures and learn a lot when working on these things. Knowledge that is extremely valuable and will save you hours. If it ever happens again, you'll know what to do.


I don't really understand what you mean about uploading pics. You can only have so many attachments, but you can use an image host to put photos on here. I used to use www.imageshack.us, but you can also use www.imgur.com

Use the forum syntax/link to paste an image that shows up in your post, or a direct link to just link to the image off-site.


Good luck with everything