Idle surge ?????

[matt98eclipse]

earlier this evening I hooked up a boost gauge in my 91 gsx. The car boost at around 8 or 9 pounds so I think that's ok? I knoticed when i do a cold start the motor's rpm's bounce between 2000 and 1500 for about 5 minutes! So I turned on the ac to see what happen's and the rpm's stay right at 1500!! Once the motor is wormed up it does a steady idle right around 850!!! What do u guys think???

 

[AWDstylez]

Start by cleaning out the throttle body and see what that does. But your FIAV is probably screwed.

 

[nataku80]

ok idle surge, the ISC is usually the problem. but you said it idles right, after you warm the car. so yeah probably you FIAV but check both.

 

[matt98eclipse]

K I will take apart the throttle body tommarow and see what happen's! What is a FIAV?

 

[AWDstylez]

Fast Idle Air Valve. It's what makes the car idle higher when cold and it's supposed to close after it warms up.

 

[matt98eclipse]

Were is the FIAV located ??

 

[AWDstylez]

Bottom side of the throttle body, closer to the engine. It's the thing that the coolant lines are going into.

 

[matt98eclipse]

K thanxs guys i will check it out! How come my vacum's only at like 11 or 12 at idle??

 

[matt98eclipse]

Please help guy's!!

 

[oldman]

Start with a thorough boost leak test.

 

[m_0ney_pit]

Most likely your TPS is going bad. If the TPS is adjusted to the non-conductive side of the line then you get a fast oscillating idle. If your ISC is going bad you get a ramping idle, which happens rather slow. If the FIAV is leaking it will cause also what you described.

Check the ISC, there is a procedure in the manual. Easy way...just unplug it and see what the idle is like it should be right around 1000 and slightly choppy if your idle is adjusted right before hand.

Its so hard to tell what idle problems are...

I would just buy a rebuilt throttle body and slap it on and forget about the annoying idle problem all together. Wait that is what I did.


Summary:
1.)If you have a spare 3 pin TPS, try it
2.)Unplug the ISC and then start the car to see if the symptoms change.(you'll get a CEL, no big deal though)
3.)Check for vacuum leaks

 

[matt98eclipse]

Im gonna try and unplug the ISC and see what happen's also I noticed a clickin noise from the throttle body when i turn the ignition on but dont start the car!! Could this be related to the ISC if not what could it be?

 

[matt98eclipse]

What could the clicking from the throttle body be???

 

[m_0ney_pit]

Must be the ISC motor clicking, but it also might be arcing inside the TPS. I'm not sure if the TPS at 5v can arc though if its bad.

Did you try to unplug the ISC?

 

[matt98eclipse]

Update: right now i just tryed to unplug the ISC and the idle didn't change one bit!!!! Still doing the rough and bouncing idle so I am takein the throttle body apart right now! Is there anything i should be lookin for?? The only thing i know to do is clean it up.

 

[matt98eclipse]

Please help guy's! I unplugged the ISC and it didn't make a diffence ?

 

[oldman]

Your idle is at -12 in HG, where are your leak test results?

BTW bumping your thread is not allowed, please don't do it again.

 

[matt98eclipse]

Sorry oldman for bumping! Im just really trying to find some help. At idle my HG is sitting around 11 or 12! I am really thinking I have a boost leak cus after I put my throttle body back on I took it for a test drive and notices I get full boost "8"psi at around 5000 rpms and it takes a while for the boost gauge to hit that amount!!! I was gonna do a boost leak test but it started to rain out here so ill have to do it tommorrow!

What rpm should full spool be at with a 14b turbo?

 

[oldman]

Low 3's if not better.

 

[m_0ney_pit]

just because you have a crappy idle doesn't mean that its specifically your TB. A jumpy unsteady idle can be caused by a vacuum leak, specifically the hose that runs to the EGR valve...if that hose isn't sealed or has a tear it will make your car idle like a big block chevy.

The hose I'm talking about is under the TB, it connects to the EGR valve which is bolted to the intake manifold runner 4.

You need to do a leak test. Or get a map of your vacuum line system from the repair manual and trace all the vacuum lines to make sure there isn't any broken, ripped, etc hoses in the system.

 

[Calan]

Did you set your idle (BISS) the proper way; by grounding both the diagnostic port at the fuse box and the one at the firewall?

http://www.vfaq.com/mods/BISS-1G.html

If not, your ISC could be at the end of it's adjustment range and the ECU can't compensate correctly.

Also, check out this article and especially the link he mentions:

http://www.dsmtuners.com/forums/showthread.php?t=191137

 

[matt98eclipse]

Hey guys thanxs for the help! Last night i did a leak down test! I found 2 major leak's! One was found to be a vacum line broke under the thermostat! The other one was the J pipe the comes off the turbo if wasn't all the way tight! So after I fixed these I started the car up and still doing the same problem!!! The only thing I think it could be is my ISC cus when I just turn the ignition on it click's really loud! When I unplug the ISC the clicking stop's. Im also thinking it may be my timeing cus it boost better but still not were is should be its doing full boost around 4500 rpm's!