Need Help with rough idle...this one stumps even me...

[GTP Version 2.0]

So i just received my new parts from ZZP. I order shorter front engine mounts (dogbones), a new Eaton bypass valve, and a throttle body spacer. So I start by changing the dogbones and everything went great. Next I change the eaton bypass valve and started up the car and everything once again is fine. I had also picked up a can of Seafoam Trans Tune and put that in (I will be putting in my shift kit in a week and wanted to run some Trans Tune before the install). I started the car again and everything is fine. Next I put on the throttle body spacer. I followed the directions, and used their new studs and gaskets provided, but now when I try to start the car, it idles INCREDIBLY ROUGH and almost dies if I don't hit the gas. I drove the car down my street and everytime I come to a stop the car will almost die. My car is a 1997 GTP with 147000 miles. I'M CALLIING ALL PROS TO HELP ME ON THIS ONE.

[CrazyHorst]

My guess is that you have an air leak after the throttle body which isn't compensated for by fuel. A smooth idle is one of the most demanding conditions as far as having even cylinder balance and a very stable 14.7:1 mixture, which the air leak would disrupt. Possibly a rolled gasket or some type of a mismatch where the castings meet up?

Maybe take the throttle body spacer back out and see what happens?

On edit: also check for a vacuum line left off or cracked during the install...exact same effect.

[GTP Version 2.0]

I took out the spacer and still nothing. Is it possible that I put too much transtune in the transmission? At this point I'm trying to think outside the box.

[GTP Version 2.0]

I tried a new combination. I took out the spacer and the gaskets that came with it. I reinstalled my old easy performance rubber gasket and everything is fine. The Garlock gaskets that ZZP sent me look great. Has anyone had problems with these gaskets before?

[doctorhrdware]

I would send ZZP an email, and see what they come up with.

[BNaylor]

Th recommendation is not to use any Garlock gaskets whenever possible. That includes the supercharger and any throttle body gaskets.

Using the Seafoam transmission additive should not cause the issue you have been having but be sure to do a pan drop service and drain it out soon. In others words don't leave it in there forever.

[GTP Version 2.0]

I also wanted to ask you guys if you know where to get a good transmission drain plug. I was gonna change the fluid in a week, run more seafoam transtune, and change the oil again.

[BNaylor]

You can get a Dorman brand tranny pan drain plug at most auto parts stores or the re-packaged version. See thread below.

Click here