I just wanted to share a solution to a problem that many people may have had with the MP TB. After I installed mine a few months back, I had high idle problems and a vacuum leak. I lived with it thinking that the throttle plate was not closing all the way. I finally found the source of my problem.

I took the TB off and noticed a notch scored into the gasket. This notch was caused by:


It is a casting flare that was left when the manifold was made. It does not get in the way of the stock TB, but does leave a 1mm gap in the lower corner of the MP TB when it is tighened down. That gap feeds air directly into the IAC motor passage. It also lets air leak in after the throttle plate.

I fixed it by carefully grinding down the manifold with my dremel until it was no longer a problem. Make sure you cover up your engine bay before you go grinding in there, and stick a rag into the manifold.



You can see how little was needed to be filed down. This fixed my problem.

-Jared

Good pics and good find. Should go in "Things we've seen before" if no one else has anything to add, imo. :thumbsup

Originally posted by jdeyo
I just wanted to share a solution to a problem that many people may have had with the MP TB. After I installed mine a few months back, I had high idle problems and a vacuum leak. I lived with it thinking that the throttle plate was not closing all the way. I finally found the source of my problem. I took the TB off and noticed a notch scored into the gasket. This notch was caused by: It is a casting flare that was left when the manifold was made. It does not get in the way of the stock TB, but does leave a 1mm gap in the lower corner of the MP TB when it is tighened down. That gap feeds air directly into the IAC motor passage. It also lets air leak in after the throttle plate. I fixed it by carefully grinding down the manifold with my dremel until it was no longer a problem. Make sure you cover up your engine bay before you go grinding in there, and stick a rag into the manifold. You can see how little was needed to be filed down. This fixed my problem. -Jared

This was true on mine as well. Luckily I had an extra mani that I ported/ polished and installed Corbin's spacer into. I had to grind down that spot also. You could actually see the gap it was causing when the MP TB was on.

Can you specify your examples of high idle problems? cause i was always uncertain about if i had a leak or not.

If it idles above 900-1000k its not idling right. Someone correct me if i'm wrong.

you are correct.

I've forced mine to idle higher than that on purpose, but that's another story. I'll move this to things seen before in a couple days.



Exile Racing Technologies: http://www.exileracing.com
una salus victus
It's holding down the garage floor right now.

I guess i installed mine with no problems then. :shrug