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1G BISS screw broken? Idle surging

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rlkohler1

Probationary Member
10
0
Feb 14, 2022
Irvine, California
Sup guys,
For quite some time now I've been trying to get my car idling properly. Long story short, i've eliminated all boost leaks, and replaced the PCV, and ISC Motor. By doing these things they have helped greatly as the idle no longer surges but is still very high (around 2k at full operating temp). I believe the trottle plate is closing properly but tomorrow I will be checking to be sure. Here is my question:

I've tried adjusting the BISS screw and it for some reason does nothing at all.. Any thoughts on this??

Any input on this or tips would be greatly appreciated. I'm pulling my hair out over this! :confused:

Thanks in advance
My problem IS the surge that's preventing me from getting my car to pass smog here in CA!
I can't find a BISS screw that sets recessed in this picture. All the ones I ordered don't screw in
I'm desperate.
Thanks
Rob Sr.

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Solution
Rob, you can fabricate your own ground for the throttle body. It can be a wire that attaches to the throttle body and goes to ground. It is used to tell the computer that you are definitely OFF of the gas pedal.
Have you unplugged the MAF and see if the car still runs (but not good)? The hose you were talking about IS the charge pipe/hose for the turbo to the motor.
Yes, the MAF was disconnected by my 2nd mechanic and he said not to run the car. The smog people told me to hook the pipe back up. They didn't do the test. I'm out of options. Thanks for all these very informative posts on DSM.

Rob Sr.
Are you sure that you don't have the fragment of a BISS screw hiding in there. It kind of looks like you might. Also is that third port in the manifold always open like that? If so, it would be hard to get a good idle.

Please fill out a profile on your car and a bigger picture of the whole throttle body/intake manifold would help.
 
My problem IS the surge that's preventing me from getting my car to pass smog here in CA!
I can't find a BISS screw that sets recessed in this picture. All the ones I ordered don't screw in
I'm desperate.
Thanks
Rob Sr.

You must be logged in to view this image or video.
It's appears the whole biss is already there
 
Are you sure that you don't have the fragment of a BISS screw hiding in there. It kind of looks like you might. Also is that third port in the manifold always open like that? If so, it would be hard to get a good idle.

Please fill out a profile on your car and a bigger picture of the whole throttle body/intake manifold would help.
@steve.....that looks like a picture of MY EVOIII manifold with the stupid red wire that went know where and I use a blue line on the first nipple and black on the second. I think that photo has been cropped from one of mine.
Just FYI
 
It's appears the whole biss is already there
Sorry to have misled you, this a picture of a BISS screwed in.
I just bought my 5th BISS screw from Ebay and it doesn't screw in!
I was only showing you the port where the screw is supposed to screw in.
Thanks for replying.
Rob Sr.
 
Please use pictures from your car or make it very clear it's an example only, so people don't waste their time trying.

I don't know how to help you without seeing your throttle body to see what's wrong.
 
Sorry to have misled you, this a picture of a BISS screwed in.
I just bought my 5th BISS screw from Ebay and it doesn't screw in!
I was only showing you the port where the screw is supposed to screw in.
Thanks for replying.
Rob Sr.
Here's one of the BISS screws I ordered from parts' houses and 2 from eBay.
These are not metal screws. They don't screw in for some reason!
Yeah, the first picture I put up was with the screw recessed in the port where it's supposed to go.
Photo 3691 is where I tried to screw in the 2nd one I just got from eBay today.
Photo 3710 is a closeup of where the BISS screw goes. Check it out.
Mine is a 2nd engine in my 1993 Eagle Eclipse.
Thanks for checking in.
Rob Sr.

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You must be logged in to view this image or video.
 
Here's one of the BISS screws I ordered from parts' houses and 2 from eBay.
These are not metal screws. They don't screw in for some reason!
Yeah, the first picture I put up was with the screw recessed in the port where it's supposed to go.
Photo 3691 is where I tried to screw in the 2nd one I just got from eBay today.
Photo 3710 is a closeup of where the BISS screw goes. Check it out.
Mine is a 2nd engine in my 1993 Eagle Eclipse.
Thanks for checking in.
Rob Sr.

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You may be right. None of the 4 shops I took it to told me that.
The idle surge stops when the hose to the turbo is disconnected.
So, they replaced my MAF sensor, turbo, ECU and nothing has worked.
No vacuum leaks.
I'm at a real standstill!
Thanks
Rob Sr.
 
Heat up a flat blade screwdriver and then melt that into the plastic BISS screw for a notch to be able to remove the old one.
 
You may be right. None of the 4 shops I took it to told me that.
The idle surge stops when the hose to the turbo is disconnected.
So, they replaced my MAF sensor, turbo, ECU and nothing has worked.
No vacuum leaks.
I'm at a real standstill!
Thanks
Rob Sr.
I guess it's worth a try.
Thanks
Rob Sr.
 
replaced my MAF sensor, turbo, ECU
Sorry about the crappy shops that have no clue how to work on a DSM.

First things first, you need a throttle body grounding strap. Its a metal bar that goes from that empty threaded screw hole on top to the throttle body mounting bolt. The way you have it now prevents the idle switch from telling the ECU your throttle is closed.
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Beyond the grounding strap, idle surge is often caused by too much air bypassing the throttle plate. There's a few possibilities:
BISS (and o-ring)
FIAV (fast idle air valve - these degrade over time and don't fully close, plenty of writeups on how to fix this.)
ISC
vacuum/boost leak
Improperly adjusted throttle cable (too tight)
Throttle plate loose or binding up

EDIT: can you please clarify what year your car is? That looks like a 1g in the pics but you flagged the post as a 2g.
 
EDIT: can you please clarify what year your car is? That looks like a 1g in the pics but you flagged the post as a 2g.

That may be because of the first picture. More likely I added the tag than a first time poster.
 
Sorry about the crappy shops that have no clue how to work on a DSM.

First things first, you need a throttle body grounding strap. Its a metal bar that goes from that empty threaded screw hole on top to the throttle body mounting bolt. The way you have it now prevents the idle switch from telling the ECU your throttle is closed.
You must be logged in to view this image or video.


Beyond the grounding strap, idle surge is often caused by too much air bypassing the throttle plate. There's a few possibilities:
BISS (and o-ring)
FIAV (fast idle air valve - these degrade over time and don't fully close, plenty of writeups on how to fix this.)
ISC
vacuum/boost leak
Improperly adjusted throttle cable (too tight)
Throttle plate loose or binding up

EDIT: can you please clarify what year your car is? That looks like a 1g in the pics but you flagged the post as a 2g.
I have a 1993 Eagle Talon (Eclipse). In 2008, I had in the shop and they drilled it out to 12.1 ratio and it blew up. I had to pay $503 for a replacement 1992 Mitsubishi engine which has now just about gone dead.
Thanks for trying to help. I suspect the screw broke off and is cluttering up the port.
Rob Sr.
 
Drilled it out to 12.1??
Meaning you had 12 to 1 compression pistons?
Yeah, I didn't authorize the work. That's why it blew up when they started it and got me a replacement engine.

I only learned it in February of 2022 that it was a 92 Mitsu.

My first mechanic got it at the first Shell I went to for help with the surge.
Nobody has conjured up a response when I wrote the surge stops when the hose to the turbo is disconnected! That's what led to my 2nd Shell mechanic ordering all the parts: MSF, turbo (the old one was fouled up) and an ECU.

Thanks, I know you guys are super smart. I'm just licensed by the IRS to do representation.
Rob Sr.
 

Attachments

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Can you explain the hose or better yet a picture? There's the big intake snorkle and little wastegate actuator.

Yeah, here's a picture and where I described the hose to the turbo. Getting it back on was a pain.

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I'm going to have to assume it is one of the intercooler hoses or intake snorkle. By doing so your MAF is seeing zero airflow and and thus the ECU reacts differently. It would likely be a similar reaction if you unplugged the MAF. This just masks your initial problem and creates another.
You have at least two issues that need fixed - the ground strap to the throttle body and replacement of the old BISS. Get those fixed and see where that puts things.
 
I'm going to have to assume it is one of the intercooler hoses or intake snorkle. By doing so your MAF is seeing zero airflow and and thus the ECU reacts differently. It would likely be a similar reaction if you unplugged the MAF. This just masks your initial problem and creates another.
You have at least two issues that need fixed - the ground strap to the throttle body and replacement of the old BISS. Get those fixed and see where that puts things.
I'll try to locate the ground strap. Hey, thanks for the help. Over & out.
Rob Sr.
 
Rob, you can fabricate your own ground for the throttle body. It can be a wire that attaches to the throttle body and goes to ground. It is used to tell the computer that you are definitely OFF of the gas pedal.
Have you unplugged the MAF and see if the car still runs (but not good)? The hose you were talking about IS the charge pipe/hose for the turbo to the motor.
 
Rob, you can fabricate your own ground for the throttle body. It can be a wire that attaches to the throttle body and goes to ground. It is used to tell the computer that you are definitely OFF of the gas pedal.
Have you unplugged the MAF and see if the car still runs (but not good)? The hose you were talking about IS the charge pipe/hose for the turbo to the motor.
Yes, the MAF was disconnected by my 2nd mechanic and he said not to run the car. The smog people told me to hook the pipe back up. They didn't do the test. I'm out of options. Thanks for all these very informative posts on DSM.

Rob Sr.
 
Solution
Boy, Cali is a mess when it comes to emissions........:banghead:
 
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