You think YOUR idles high...pshh

[1gcrazy]

Hey guys i'm having ANOTHER issue. I've searched a bunch and I keep seeing people with like 2k idles....i'd LOVE to have an idle that low. My cars idling at like 4k rpm's. I changed the TPS and the ISC with good units and i'm getting the same effect. Since I changed out those units i'm actually about 500k higher than before. I'm a bit baffled. Even with the throttle cable unpluged from the tb its still doing it except its bucking kind of. It'll rev then drop like somethings trying to lower it....?

Let me know if you have any ideas...this car is a 91 gsx completely stock. Someone suggested the maf being bad...?

BTW its not throwing any codes either.

 

[Underdog378]

Did you check the BISS? Is it even still there?

 

[BISHILVR]

If it does "throw" any codes make sure that you stand clear of it so you dont get hit. I would check the closed throttle position switch, make sure that it is adjusted to a position that is'nt preventing the throttle from fully closing. Next I would blame the fast idle air valve. Do you still have coolant lines connected to your throttle body?

 

[oldman]

Pull your ECU and check for capacitor leaks.

 

[Glliw]

I'm having the same problem actually. I can't figure it out either. The ECU isn't it because I just put in a FFWD rebuilt eprom ecu and it still does it. The TPS voltage checks out fine and there are no vac leaks or lines missing.

 

[1gcrazy]

Did you check the BISS? Is it even still there?

Biss screw IS still there. It looks as though its in pretty good shape. I could pull it out and check the o ring...?

If it does "throw" any codes make sure that you stand clear of it so you dont get hit. I would check the closed throttle position switch, make sure that it is adjusted to a position that is'nt preventing the throttle from fully closing. Next I would blame the fast idle air valve. Do you still have coolant lines connected to your throttle body?

Yeah those TEL get pretty pissy...
Closed throttle position switch...thats a new one on me. I did see the throttle and it is fully closed. FIAV? I've heard of it but dont remember what the issues were...I'll look into those both. Yes the coolant lines are still attached.

Pull your ECU and check for capacitor leaks.

I did pull the ecu at an earlier time and I didn't smell any fish and i forgot to check the caps. i was looking for eprom only... I'll double check...

 

[1gcrazy]

Ok so I havn't had a chance to bypass the FIAV but i've been researching. I'm curious, Is there anyway to rebuild the bottom end? You can rebuild EVERYTHING just because a wax piece goes bad doesn't mean you throw the whole thing away...anyways.

 

[BISHILVR]

just because a wax piece goes bad doesn't mean you throw the whole thing away...

Unfortunately in this case it pretty much does. I dont think that it is a serviceable piece. Sometimes the gasket (o ring) under there goes bad (splits) and will cause the problem.

 

[GVR4592]

You might have a really large vacuum leak somewhere, I'd do a boost leak test.

 

[1gcrazy]

thats first priority after i swap throttle bodies...

 

[DiamondStarAwd]

I have the same problem as you do. Idle surging. AFter it warms up it kind of jumps between two rpm's rising and falling rising and falling.. yea. Its so cold out I havent had a chance to look at mine.

 

[1gcrazy]

I have the same problem as you do. Idle surging. AFter it warms up it kind of jumps between two rpm's rising and falling rising and falling.. yea. Its so cold out I havent had a chance to look at mine.

I dont have idle surge at the moment. What are your current rpms during this??

 

[DiamondStarAwd]

Warms up at like 2k. Then drops to 1500 and bounces between 1800. up and down up and down up and down. Also running very rich. Have unburnt fuel coming out the exhast and the ground behind it is black haha. fyi motor only has 250 miles on it soo

I've just yet to even touch it. boost leak test, and checking to see if the throttle closes all the way is first on the list.

 

[silver eclipse]

How are you brakes? If the booster diaphram is bad it can cause a vacuum leak.
It definatly sounds like a major vacum leak. Do like mentioned before and boost leak test it.
-Chad

 

[1gcrazy]

How are you brakes? If the booster diaphram is bad it can cause a vacuum leak.
It definatly sounds like a major vacum leak. Do like mentioned before and boost leak test it.
-Chad

I should be doing that today. Hopefully.

The brakes as far as I know WORK at least. Honestly, I havn't paid much attention but when you dont notice them is probably good...

I thought i had a vacuum tester around the garage but its such a mess it'd take me days to find it....any other way of testing that? I've got a spare on laying around

 

[silver eclipse]

You can use one of those special smoke machines to check for a vacum leak (sorry I cant think of the name right now), gently start pinching hoses, or use brake clean and spray it around where the intake manifold meets the head, all with the car idling. Becareful not to catch the brake clean on fire (it generally wont, just my disclaimer ). You may have blown out the head gasket or had the manifold crack.
-Chad

 

[1gcrazy]

So....I fixed it last night. I turned the biss screw all the way in and it almost died so i backed it out and viola! Amazing how someone ####ing around with a screwdriver can cause so much headache.
Anyways, thanks again guys!

 

[Talesin]

Also check that your idle sensor switch is hooked up and working... the reason a lot of our cars 'surge' is that when the ECU sees that the car is idling, it has a cutoff... if the rpms go over 2000 or 2500 (can't remember which), the ECU cuts fuel for a second. If your car was idling at 4K without surging, sounds like the ECU isn't seeing it as idle-on at any point. Might also be a throttle cable misadjustment, holding the TB actuator open just enough not to depress the switch.

Also don't forget to ground the idle set terminal on the firewall when you make an adjustment to the BISS, or the ECU will try to 'fight' it. Can also make a change and reset the ECU (I do this by pulling the lower-right fuse on the interior fusebox for 30 seconds or so), but that's kinda half-assed and loses you your radio presets as well.

 

[1gcrazy]

I fixed it....my biss screw was damn near OUT. I turned it all the way back in and its idleing just fine. thanks though