ISC & FIAV delete still idle surges?

[turbo addict]

I have a 1989 mirage turbo, It has a 1991 tb on it and I just did the tb block of plate, partly to clean the engine bay up partly to get rid of idle surge.
Well the car runs fine but I still have idle surge?? it will surge from 900rpm to about 1500rpm and is really slow doing it. I have checked for leaks and I think that I have them all fixed. What else could it be??? mods should be on my profile.

PS if this is in the wrong spot sorry in a rush to school.

 

[Avionixx]

So is the BISS fully bottomed out right now?

 

[flinguist]

This idle surge vfaq may help you. http://web.archive.org/web/20040730025938/http://www.vfaq.com/mods/wayback/BradBauer/engine/surge.html

 

[turbo addict]

OK, I just had the throttlebody off and cleaned it (not very bad to begin with) when I did the block off plate.
The biss is not all the way in but most of the way.
I have no IAC.
I have no FIAC.
I have no EGR.
I still have idle surge??
Any ideas??

 

[pneumo]

Watch the O2 volts on a logger and see if the surge follows the rise and fall of O2 volts.

 

[blcknspo0ln]

OK, I just had the throttlebody off and cleaned it (not very bad to begin with) when I did the block off plate.
The biss is not all the way in but most of the way.
I have no IAC.
I have no FIAC.
I have no EGR.
I still have idle surge??
Any ideas??

Did you replace your TB shaft seals? Did you do a boost leak test?

 

[boostnhard]

so by removing all of this the engine should be smooth as a baby rite?

 

[44pirate]

Vacunm leak. Do a boostleak test.

 

[H82lose91]

Where does it idle with the closed throttle switch unplugged? Id start with the Biss 2 to 2.5 turns out. You may need to adjust the closed throttle position to get it dialed in.

 

[selser420]

I've been running a lower TB block off for two seasons with no surge issues. I would boost leak test and change the TB shaft seals.

 

[2GeNTSi]

Yeah I would check on the TB seals as well and boost leak. If you have aftermarket ic pipes with thin flanges like dejontool (I have them and they leak like crazy) you're gonna have to get some RTV and seal it up.

I did this and ran a boost leak just to make sure and it got rid of majority of my boost leaks. My car pulled a lot harder and it didn't take forever to build full boost in the end.

However, I'm still having a weird idle problem as well. I swapped the bottom half from my 2G TB to my 1G TB and also put in a bypass plate (retains IAC) after having it rebuilt from John at Throttlebodys.com. It rid my car of this weird low rpm bucking issue but when my car gets to operating temperature, the idle is around 1.5-2k. My IAC is new and I tested it to be fine, however I unplugged it one day to see if it would fix anything and it runs EXACTLY the same way as if it was plugged in.

I researched and thought it might be the CTS but I can't seem to find the exact one that I have on my car (they all have a different shape ).

 

[twicks69]

Turbo Addict - did you ever figure out your problems with the idle surge issues?

Did you replace the O-ring on the BISS as well? Did you use the BISS plug or silicone up the BISS once you had it adjusted? If the BISS O-ring gets old, it will cause a leak and give you idle issues. As well, the throttle body shaft seals are always a good thing to replace. Just remember, if you are going to do this, be sure to properly mark the shaft springs so you can re-install them to the proper tension. If it is too loose or too tight, it will not be a good thing. I usually take a Sharpie and mark a straight line across the entire width of the TB shaft spring.

If you are still looking for throttle body shaft seals, the Mitsubishi part number is: MD614219 (I believe this part number is only for a 1990, but I cannot remember off the top of my head anymore.) As well, the shaft seals can be purchased through different vendors. Chicago Rawhide, part # 3930 CR 10x14x3 HM4 R (It is also the same part number from SKF).

You can also find the technical information regarding the construction and dimensions of the throttle body shaft seals and purchasing of the parts here: https://ec.kamandirect.com/kamandirect/catalog/part.jsp?CPN=&ORIG=FindPartV1&PARTID=20673657


You can also purchase them from Extreme PSI, Slowboy, MachV, and other places.
Mach V - Throttle Body Seals
Slowboy - Slowboy Racing, Inc. :: DSM :: Intake :: Misc. Intake Parts :: Mach V Throttle Body Seals
Extreme PSI - (Call to order)


As well, the BISS screw part number is: MD614948

The BISS screw O-RING part number is: MD608806

The BISS screw plug part number is (I usually use Permatex Ultra-Black RTV instead): MD614150


As well, here is a good technical writeup concerning fast-idle/idle-surge issues and troubleshooting.

Terry's Talon Troubleshooting Tips #3 - Fast Idle (aka. Idle Surge)

Good luck with the problem if you don't have it figured out yet!

 

[Happys_TSI]

Watch the O2 volts on a logger and see if the surge follows the rise and fall of O2 volts.

If so then what? my car is doing this.