1G TB to 2g Swap DOESN'T work

[GVTalon]

After 2 weeks of pure diagnosing hell, I've come to the conclusion that a 1G TB on a 2G does not work.

I followed RRE's instructions to the "T", 4 nipple 1G TB, swapped the TPS bored the mani, checked the TPS position, everything. When I start up the car and I have idle surge. In trying to diagnose the problem I pulled all the emissions stuff out and built a pressure tester to make certain there were no leaks. Still surge. I even went as far as haveing the 1TB cleaned at a dealership and purchased a brand new TPS and ISC from "Satan" along with new gaskets. Installed it, and still surge. I ripped the TB assembly out of my 95, put it on the 97 and the car runs mint. So the problem has to be the 1G TB; it must let to much air pass at an idle for a 2G.

If anyone can think of something I missed, please let me know, I'm all ears.

 

[g96nt]

did you adjust the BISS?

did you check the Condition of the o-ring around The BISS?

also, there are seals inside the TB that go After some years...
maybe this is your issue?

I know my '95 was tempermental.

but, switching To the '92 TB cleared everything up.
instead of paper gaskets, I used ultra grey.

it could be the AIC in the TB.... did you run the coolant lines through the TB?

what year is your 1g TB?

 

[GVTalon]

Don't remember the year of the TB, I bought it from a guy parting out his wrecked car. I turned the BISS in till it bottomed out and the idle dropped only around 100 RPM. I capped off the coolant lines.

It must be the internal seals then.

 

[g96nt]

no..... capping The coolant lines Will give you a 12-1700 idle always... or untill the under-hood temps get hot-enough To melt the wax-ball in the TB

until then.. your car is *warming up*

try Running the coolant lines back Through, I'm Sure Things Will change.

 

[GVTalon]

Really, Hmm. Why did the 2G TB work with no coolant lines? Will reconnecting the lines also drop the start-up idle. Because right now start up idle is 2000 then drops to the surgeing 1200-1700? I'm going to try installing the lines anyway. Thanks for helping.

 

[larryd]

yup.. i heard the same thing.. becuase there is a temp sensor beyond the throttle body that you can adjust the biss for but once the car is warmed up it will surge badly.. this was actually on turbo4wd's page I believe.. I was going to bypass the coolant lines myself until I read it

 

[GVTalon]

I quickly skimmed his site, but it seems he had a problem with the car idleing low caused by no coolant lines. Mine runs high from the start (2000 as soon as it starts), I just can't picture the coolant instantly warming the TB the second I start the car and the idle being normal. Anyway I'm going pressure test the coolant part of the TB to make sure the gaskets inside aren't bad and coolant possibly entering the engine, then I'm going to reinstall the hoses and try it out. Thanks for the suggestions.

 

[larryd]

hope it works for ya, keep us clued in..

 

[GVTalon]

Well I attached the coolant hoses. Started up the car and it idles at 2200 RPM for about 1 minute. Then as the engine heats up the idle drops. However no more surge. After about 4 minutes running at idle the RPM dropped to 1100. I turned in the BISS all the way and got the RPM down to 900. I let the engine cool and started it up again. Same thing, high start idle and now drops to 900 after about 4 minutes. Rev the engine and it drops smoothly to 900 every time. I haven't driven it yet, but at least the surge is gone. So hopefully my last question is...Should I be satisfied with such a high start idle and running fine after warm-up?

 

[g96nt]

your idle is still pretty high....

did you just re-connect the ECU?

 

[larryd]

now that you got rid of the surge maybe play with the tps?

 

[GVTalon]

I started up the car this morning and the initial start-up is still around 2100 RPM. However now the idle comes down a little quicker than yesterday, around 3 minutes to reach its lowest idle which is now 750 rpm. It idles at 750 smooth and steady (I let it idle for 30 min). I'm just a little concerned about such a high idle at the start, but other than that I'm really happy there is no more surge.

 

[95GST]

I'm new on this board, but I saw your post I signed up because I wanted to help out

In my experience it's possible for the car to idle surge after resetting the ECU. It may go away after a day or two.

Idle surge is can be caused by BISS screw backing out so far, bad ISC, or not hooking up your coolant lines

In other words, any situation where you have too much air going into the engine than the ECU expected, you can idle surge.

Since you didn't connect the coolant hose, the FIAV now doesn't close when the ECU expect it to. The ECU assumes the FIAV's actions by looking at the coolant temperature. Your FIAV will be open all the time unless the TB gets pretty hot from engine heat itself, this can give you idle surge, and prolonged high idle.

BTW, your initial cold start up idle would not matter with or without the coolant lines, since the TB is at ambient temp initially.

If you want to remove the coolant hose properly, you will need to remove the lower part of the TB and fill it up with RTV or JBWeld. I have done this with good stable idle. It doesn't rev as high during cold start anymore.

The other suggestion would be to put the coolant lines back on. Looks like you have done this, and getting better after the ECU relearns.

You shouldn't have to bottom the BISS out to get 750 RPM, but every TB is adjusted differently..

 

[GoFastTSI]

Pull MPI fuse for 15-30 seconds to "reset" the ECU, then start car and let idle for at least 10 minutes WITHOUT touching the accelerator pedal. This will reset your fuel trims and should take care of your idle as well. Just remember, do not touch the pedal for the 10 minutes it is idling.

Joe

 

[cb7587]

MPI fuse?