1G Tried Replacing TB gasket to help Idle surge, car will no longer hold rpm

[AdroitPostal]

A little background first: I bought this 93 TSi that's been sitting for 8 years. I've replaced the transfer case, a few odds and ends, the starter, new battery, and it runs fairly good now. However, It's had a bit of idle surge ever since I've gotten it running. It seems to do it the most when my engine is still cold, or after I've been on the gas for a few minutes and let off to go into neutral.

In an attempt to fix my Idle surge in my 93 TSi, I replaced the TB gasket as it showed obvious signs of a leak however, I believe my lack of research into parts relating to this fix has screwed me over. The car was starting fine after the new gasket was installed, but I likely believe this is because the engine was still warm.

Now, it has a very hard time starting up, the crank is strong, but when it does start it will flutter out without someone giving it a little gas. it seems like I've just escalated the idle surge issue even more. Upon reading Terrys Talon Troubleshooting tips #3, my Haynes manual, and based on how my car acted before I replaced the gasket, maybe a bad TPS, maybe bad O2 sensor?

Going to try and find a way to test the O2 sensor now.

 

[Turbski91]

Sounds like you have a boost leak when the engine is cold. Another possibility is a bad FIAV. Did you use OEM gaskets, and the correct ones? I believe there are a couple different ones. I would double check the gaskets you purchased are correct, and are installed in the right orientation. Sounds suspect that it got worse after doing that work. A good way to find a boost leak is to spray brake clean in spots you suspect a leak, and if the idle stops surging when spraying a particular area you found your leak.

Also you didn’t mess with the BISS screw did you?

 

[FIBA M - EC17PSE]

simply put you need to do some maintenance and its best to strip the TB and replace all the seals and gaskets and o rings. sitting can perish seals and would be a wise time to do this cheap fix to make it up to date and 1 less thing to worry about plus DO THE FIAV bypass. it will be the best solution since the fiav wax can cause high idle if its old and not working correctly,

 

[AdroitPostal]

Sounds like you have a boost leak when the engine is cold. Another possibility is a bad FIAV. Did you use OEM gaskets, and the correct ones? I believe there are a couple different ones. I would double check the gaskets you purchased are correct, and are installed in the right orientation. Sounds suspect that it got worse after doing that work. A good way to find a boost leak is to spray brake clean in spots you suspect a leak, and if the idle stops surging when spraying a particular area you found your leak.

Also you didn’t mess with the BISS screw did you?

I used a Rubber Cellulose Gasket for the throttle body. i used soapy water after installing as i was able to start the car after installing it, i couldnt find another leak pertaining to this issue. i didnt check my FIAV when i had everything disassembled. ill take it apart and clean everything up real nice and see what happens. I didnt touch my BISS screw, but is it possible i stretched my throttle cable when removing my throttle body??

simply put you need to do some maintenance and its best to strip the TB and replace all the seals and gaskets and o rings. sitting can perish seals and would be a wise time to do this cheap fix to make it up to date and 1 less thing to worry about plus DO THE FIAV bypass. it will be the best solution since the fiav wax can cause high idle if its old and not working correctly,

going to give this a shot and see what happens. whats the best place to find the other seals and o rings? Im having a hard time trying to find them, ive only been able to find that main tb gasket.

 

[Turbski91]

I used a Rubber Cellulose Gasket for the throttle body. i used soapy water after installing as i was able to start the car after installing it, i couldnt find another leak pertaining to this issue. i didnt check my FIAV when i had everything disassembled. ill take it apart and clean everything up real nice and see what happens. I didnt touch my BISS screw, but is it possible i stretched my throttle cable when removing my throttle body??

I doubt you stretched the cable. Unless you moved the throttle cable adjustment screws?

 

[FIBA M - EC17PSE]

going to give this a shot and see what happens. whats the best place to find the other seals and o rings? Im having a hard time trying to find them, ive only been able to find that main tb gasket.

Extreme PSI has a good parts selection. they do everything needed.

 

[1990TSIAWDTALON]

I just did 2 TB's.
This might give you a little insight. I didn't do any rebuild video but I think you can get the drift.
LMK if you need any help/tips/pointers.
Marty

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[DSMPT]

A little background first: i bought this 93 TSi thats been sitting for 8 years. I've replaced the transfer case, a few odds and ends, the starter, new battery, and it runs fairly good now. however, It's had a bit of idle surge ever since I've gotten it running. it seems to do it the most when my engine is still cold, or after I've been on the gas for a few minutes and let off to go into neutral.
In an attempt to fix my Idle surge in my 93 tsi, I replaced the TB gasket as it showed obvious signs of a leak. however, I believe my lack of research into parts relating to this fix has screwed me over. the car was starting fine after the new gasket was installed, but I likely believe this is because the engine was still warm. now, it has a very hard time starting up, the crank is strong, but when it does start it will flutter out without someone giving it a little gas. it seems like I've just escalated the idle surge issue even more. upon reading Terrys talon troubleshooting tips #3, my Haynes manual, and based on how my car acted before i replaced the gasket, maybe a bad tps, maybe bad O2 sensor?? going to try and find a way to test the o2 sensor now.

Have you ever adjusted the throttle body properly by yourself? If not, before going to try something else, should check that your throttle body is grounded well and the TPS, BISS, throttle plate and throttle cable are adjusted properly.

 

[AdroitPostal]

I just did 2 TB's.
This might give you a little insite. I didn't do any rebuild video but I think you can get the drift.
LMK if you need any help/tips/pointers.
Marty

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Appreciate the help Marty! that o-ring tool looks pretty handy, where'd you manage to pick one of those up? Just about to take my TB assembly out of my vehicle for a deep clean, just ordered new seals and gaskets

Have you ever adjusted the throttle body properly by yourself? If not, before going to try something else, should check that your throttle body is grounded well and the TPS, BISS, throttle plate and throttle cable are adjusted properly.

I think whats screwing me is I may have tampered with the throttle cable. Only thing I did to TPS was disconnect electrical plug, BISS screw is untampered, I didn't take the throttle plate off of the TB, but now I can't get it to even start this morning.

 

[AdroitPostal]

Ok. So I have taken the TB off and done my best to give it a good clean. Upon this inspection I realized my throttle plate was slightly sticking in the closed position, no longer an issue after cleaning. I also noticed that the outer gasket of the TB connecting to intake piping appeared to be makeshift sealed with some kind of silicone. I proceeded to cut a new gasket for this out of Rubber Cellulose. It also appears that the previous owner had tried tampering with what I believe is the BISS screw with a pipe wrench or pliers of some sort? Teeth marks on it. Working on installing and putting everything back together now, we’ll see if this quick clean did anything.

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Alright, I got it running again but idle surge is still there. Bouncing between 1500-1900 rpm. I ordered seals for FIAV and o-rings for TPS.

Going to park it until they arrive.

 

[pauleyman]

It also appears that the previous owner had tried tampering with what I believe is the BISS screw with a pipe wrench or pliers of some sort? Teeth marks on it.

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That isn't BISS. It's the idle position switch.

 

[AdroitPostal]

That isn't BISS. It's the idle position switch.

Sorry, I should’ve looked a bit harder at some diagrams. So it just makes contact to metal on the part where the throttle cable is attached to the throttle plate? Does this just tell the ECU that the car is idling?

 

[pauleyman]

Sorry, I should’ve looked a bit harder at some diagrams. So it just makes contact to metal on the part where the throttle cable is attached to the throttle plate? Does this just tell the ECU that the car is idling?

No. It tells the ECU the throttle is closed.

 

[92AWDHX40]

Marty build one for me years ago thanks man its still holding up as a spare.

 

[DSMPT]

Alright, I got it running again but idle surge is still there. Bouncing between 1500-1900 rpm. I ordered seals for FIAV and o-rings for TPS.

Going to park it until they arrive.

I already asked this above but once again, did you make sure if the throttle body is grounded and TPS, throttle plate, BISS, cable are adjusted properly? If all have been done, check for vacuum leak and ISC. You have to start from those, after doing those if still the idle is unstable, then should go next step. Otherwise you would keep unnecessary spending money and time.

 

[1990TSIAWDTALON]

Appreciate the help Marty! That o-ring tool looks pretty handy, Where'd you manage to pick one of those up?

@snowborder714 can help you out with a great tool

 

[AdroitPostal]

I already asked this above but once again, did you make sure if the throttle body is grounded and TPS, throttle plate, BISS, cable are adjusted properly? If all have been done, check for vacuum leak and ISC. You have to start from those, after doing those if still the idle is unstable, then should go next step. Otherwise you would keep unnecessary spending money and time.

my apologies, i thought that i had answered this previously. ground connection is strong to throttle body, TPS pins are clean and hasn’t been disconnected, so should be adjusted just fine. throttle plate is in correct adjustment, cable is still in same position. will check for a vacuum leak tomorrow. ISC? sorry if i’m just blanking here.

 

[twicks69]

Quick dumb questions, but are you using fresh fuel? Boost leak test? Fuel filter on pump and filter canister replaced?

 

[AdroitPostal]

94 is in the tank at the moment, about 3 weeks old. fuel filter and canister have been replaced, i’ve done my best to give it a basic tune up maintenance wise. i’ve never done a boost leak test, my cars before talons have been NA, how do i go about testing such?

 

[1990TSIAWDTALON]

You build one of these to clamp onto the front of your turbo, then add compressed air and listen and spray soapy water on all connections. This PVC fitting came from a hardware store, then drill a hole for a bolt in tire valve. Put on a PC of rubber hose and two HD clamps (T bolt) to complete the unit. We call them BLT's (boost leak testers).
Clamp it on REAL TIGHT on the turbo so it doesn't fly off under pressure (ask me how I know), or it could hurt you.
Marty

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[AdroitPostal]

You build one of these to clamp onto the front of your turbo, then add compressed air and listen and spray soapy water on all connections. This PVC fitting came from a hardware store, then drill a hole for a bolt in tire valve. Put on a PC of rubber hose and two HD clamps (T bolt) to complete the unit. We call them BLT's (boost leak testers).
Clamp it on REAL TIGHT on the turbo so it doesn't fly off under pressure (ask me how I know), or it could hurt you.
Marty

Marty you did an absolutely amazing job of simplifying that for me! i’ll have to make a run to home depot and see what i can’t rig up today, i’ll make sure it’s super tight as compressed air is no joke haha. i just want to say you’ve been so helpful on this thread, gave me a few nuggets of good information that’s for sure

 

[Justin DuBois]

Marty you did an absolutely amazing job of simplifying that for me! i’ll have to make a run to home depot and see what i can’t rig up today, i’ll make sure it’s super tight as compressed air is no joke haha. i just want to say you’ve been so helpful on this thread, gave me a few nuggets of good information that’s for sure

You can also put a fitting that will hold the air compressor hose in the cap vs a Schrader valve. I use the regulator on the compressor to hold - say 30psi, and then my hands are free to touch hoses and such:

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[pauleyman]

You can also put a fitting that will hold the air compressor hose in the cap vs a Schrader valve. I use the regulator on the compressor to hold - say 30psi, and then my hands are free to touch hoses and such:

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I did this also. I put an air fitting and just regulate down.

 

[1990TSIAWDTALON]

Yeah I went to one of these on a short piece of air hose also. Safer

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[chrisman287]

Do you have ecmlink? Boost leak test for sure but I would also make sure the tps and biss screws are calibrated correctly. I almost guarantee you they’re not. Sas and throttle cable might not be either