TOPIC: 1990 Buick Lesabre 3.8 Liter

I am going to start off asking for a little advice from my fellow groovers after cleaning the throttle body of our newest vehicle in the garage. Yes I just cleaned it seeing that it was getting late and we are traveling for the holiday, and where we travel to see family people actually shut down tow businesses for holidays. And with 28 years and 87k miles, I think its due for a good can or two of carb spray.

This car has a port on both sides of the throttle plate and they are approximately 3/8" square and 1/2" deep, is the correct procedure to fill this up on the back side in order to cut the groove correctly? I have done quite a few buicks but this engine is the first I have seen this configuration, the mid 2000 years look like the normal GM fly by wire bodies.

I'll upload some pics below, please chime in with your thoughts.


This is what I started with.


After the cleaning.


Ken

Hi Ken those are the ports for the IAC valve. Ron told us years ago about restricting airflow through the Idle Air Control ports. You want to remove the IAC valve on this TB and clean it up, and the passage it goes in too.

Two reasons for restricting airflow thru the IAC. Ron gave the first; some IAC's will stay open and create what amounts to a vacuum leak. Second, as like this TB, flow out of the port below the plate can disturb the Groove's waveform. I've posted several times showing ways to use JB weld to modify these ports. OEM's seem to provide huge IAC ports, maybe anticipating these will get REALLY badly grunged up, and still allow IAC to function?

Even if you don't modify the IAC ports, you want to pull the IAC valve and get it and the ports inside clean- 'cause these can get dirty enuf to prevent the IAC from closing. THAT could cause runaway idle RPM'S when least expected' like at a stop or red light....!

Check around in Service Bulletins, and the GM and Ford categories, I've posted w/ pics, ways to handle this.

feel free to ask any Q/A you might have, Ken. Hope you and yours had a great Turkey Day!

Tracy G

Hi Ken, I had more time to study the pics of this Buick TB. The bore wall right under where the Groove would go looks dangerously thin, alright. But I've got an idea that might work.

With the IAc pulled, you can study the config. of the entire IAC port. IF the shape of the upper section where the IAC valve goes allows it-- It could be possible to fashion a port-in-a- port using a piece of copper tubing. A piece of 1/4" ID, or whatever similar ID, tubing goes into the IAC port. Bent in a shape that has it against the outboard wall of the port's exit. This to allow epoxy fill in the lower port, to backfill under the Groove area. I cant say exactly, since I don't have it in my hands- but bent into sort of a letter J shape might be it. If alignment can be discovered, and marked w/ a Sharpie, maybe instead a complete fill of the lower IAC port, then drill the new port out. Clear box tape over card stock, and taped over rubber hose, work well when making epoxy dams/ molds, etc.

Another obvious benefit to this is to reduce airflow interference w/ the Groove waveform from the IAC exit port.

That's what come up with from what I see, Ken. Thanks for all your posts over the years, and Merry Christmas!

Tracy G

May need to look into where EGR and PCV valves are at . My 1994 Lesaber 3.8 L has PCV valve inside EGR valve which is not good for rerouting PVC lines
geraldc

Actually, Gerald, the PCV Valve is under the MAP sensor. The EGR leads directly from the Exhaust to the intake manifold. This is another vacuum leak we will be dealing with in the next few months.

To PROPERLY seal the PCV valve on this type of configuration you need to remove the housing holding the PCV in place, and remove the valve. Then, look at the seating area for the valve. You will find there is a small hole off to the right. It is THIS hole that needs to be plugged off.

What I have done in the past to successfully complete this is to take a RUBBER vacuum cap that fits (blunt end down) into the hole. Then, I take a short bolt and screw it in the open end, so that it is tight.

Of course, if you clean it and then sand it a little, you can simply plug it with JB-Kwik and be DONE with it!

Plugging the PCV valve here will cause EXTREME variables in your fuel delivery as it removes the vacuum from the MAP sensor.

Just sayin...

Ron

OK Thanks Ron maybe I am looking at EGR wrong way
geraldc