Boost Leak and High Idle

[ChunkyLover53]

I recently replaced my ISC. Before that the car had classic symptoms of a bad ISC such as almost won't run with A/C on. When I replaced the ISC, the idle was not only fixed but it left me with a high idle. My car now idles around 2000 RPM. I figured I would probably have some sort of boost leak so I did a boost leak test. I found a monster leak between the throttle body elbow and the throttle body. I removed the elbow and cleaned up the gasket which looked pretty good and that actually fixed the leak. I still have a boost leak near the throttle body, but I can not find it. I was a little frustrated so I pulled off the plug to the ISC and started the car to see what would happen. To my disappointment my car idles no differently with the ISC connected or disconnected (around 2000 RPM). I was hoping to see a change maybe back to how it was with a bad ISC.

1. How would you approach the leak near the throttle body? Is the correct way to do the soapy water test to just put it in a spray bottle and spray the water all over the throttle body and look for bubbles?

2. Should the car's idle be affected by having the ISC unplugged?

3. Would a FIAV block off plate be helpful in my situation?

Any input would be greatly appreciated.

 

[ZmanIV]

monster leak bad
this is unmetered air entering the system
bet you are running real lean
seal that leak before you do anything else.

 

[Street_Killer]

More then likely your isc is not set right.

 

[ChunkyLover53]

I fixed one leak, but can not find the second. It is definately around the throttle body. If someone could tell me about locating the leak that would help (maybe soap with water test only I don't know exactly how to approach that. Should I just start dumping soapy water on my TB?). What should I do about this ISC problem?

 

[Spades]

You need to turn down your idle speed to 900 first, and then see if unplugging your ISC makes a difference. At 2000 RPMs your ISC cant possibly do anything to correct your idle speed.

 

[ChunkyLover53]

You need to turn down your idle speed to 900 first, and then see if unplugging your ISC makes a difference. At 2000 RPMs your ISC cant possibly do anything to correct your idle speed.

Thank you for the response about the ISC, that clears up the ISC question. If anyone could give me input on question 1 or 3 at the top that would be appreciated as well.

 

[ZmanIV]

spray brake cleaner onto the intake pipes. when it enters the airstream your rpm's will rise.

 

[ChunkyLover53]

I found a major boost leak coming from the BISS. Is that an indicator that the O ring is bad? Also if anyone has an idea why replacing the ISC would make the car show signs of high idle I'd be interested as well.

 

[ekanddsm]

I would rec two things unplug the isc, screw the biss all the way in, after you replace the oring,replace both throttle body gaskets, and do another boost leak test. You may still have throttle shaft seals leaking but at least you'll have pinpoint it down.

You do have a boost leak tester?

 

[got_Dsm_NY]

i would spray soapy water on all the pipping and around the t/b if you see it dry up you found yourself a leak, if not then your good.. you say the leak can be around the t/b i would change the seals and gaskets n try another boost leak test that should help the idle out a bit n then you slightly adjust your idle

 

[ChunkyLover53]

I would rec two things unplug the isc, screw the biss all the way in, after you replace the oring,replace both throttle body gaskets, and do another boost leak test. You may still have throttle shaft seals leaking but at least you'll have pinpoint it down.

You do have a boost leak tester?

I will replace the o ring and both TB gaskets. Then I will check it again. And yes I do have a boost leak tester.

i would spray soapy water on all the pipping and around the t/b if you see it dry up you found yourself a leak, if not then your good.. you say the leak can be around the t/b i would change the seals and gaskets n try another boost leak test that should help the idle out a bit n then you slightly adjust your idle

I did the soapy water test, and there were major bubbles coming from the BISS screw. I will replace the seal and gaskets.

Thank You both for the replies! I know the o ring and gaskets aren't that expensive, but I just wanted to make sure I am on the right track. I have never really dealt with not so obvious boost leaks before.

 

[ChunkyLover53]

So I thought I would keep everyone updated on my progress of diagnosing my idle problems. I replaced the BISS and O ring which were leaking and I got about a 100 rpm idle drop. So I popped the Throttle Body off tonight to get at both gaskets and inspect the lower area of the throttle body. I am going to take it apart tomorrow and let you guys know what I find.

 

[ChunkyLover53]

Ok, so I took apart the TB, and now want to install a FIAV block off plate. Any help with the questions below will be appreciated.

1. Should I use the rubber gasket even though the block off plate will be in there?

2. How do i block off the coolent lines now that they are not being used?

 

[ChunkyLover53]

I replaced the 2 gaskets on each side of the throttle body, and the rubber gasket between the FIAV block off plate and the throttle body. I started her up for the first time in 2 weeks and the idle was fixed. Obviousely the problem was either the ISC that i replaced or the FIAV. After I get the car smoged maybe I will try to find the actual problem instead of applying the band aid fix. I started it up for the first time in 2 weeks, but drove it tonight for the first time in about a month. The saying so true, "it may be running rarely, but when it is..... so fun to drive"

Just wanted to let everyone know my progress, cause people might be going through the same thing. Block off plate was ordered through JM Fabrications.

 

[joobienooner]

Was your car only idling at 2000 rpm until the car warmed up or would it continue while the car was warm? My car idles at 2000 until it warms up a little and the idle slowly goes down to normal.