I need to replace the throttle body on my 98 Bonneville. What years fit this application? I did search forum but didn't find anything specific in regards to interchange.
Thanks,
Jim

If you are normally aspirated, any 1996 to 1998 TB from a normally aspirated (not supercharged) 3800 motor will be a direct swap. Bonneville SE, LeSabre, Olds 88, Grand Prix GT, Regal LS, et.al.

If */c, same years but from the */c versions of those cars (Bonne SSEi, Grand Prix GTP, Regal GS)

What is wrong with your TB that it needs replacing? If it is a bad sensor, they are replaceable individually.

Here is the story. I thought I had a vacuum leak as I could vary the pitch of this whistle type noise by how far I pressed down on the gas pedal. I verified I had no vacuum leaks. A friend of mine a GM tech told me yes there was a bulletin on the 98 models. He pulled the plenum, and did mods of some sort and got about 75% of the whistle gone. He said the other option to get the remainder of the noise out would be to change the throttle body. We already pulled and checked each sensor on the throttle body for leaks and all were fine. I checked entire forum in regards to vacuum leaks before posting as it makes sense that this one may have already been addressed. Research before posting is the better choice. Has anyone seen this or heard of this before? Very annoying noise. Thanks much for the input on the interchange as I don't have that book for reference. 4th Bonneville too.

If you have checked all the vac lines and found no leak you can also check the gaskets. Is this car supercharged or non supercharged? If the car is N/A you will want to check over the UIM for cracks and such.

Non supercharged basic 98 Bonneville. Most people would never hear this whistle type noise but I would like to completely eliminate it. Also it run way better after he pulled the plenum and did the GM mods to fix this. Wierd. So far I had 3 very experienced guys look investigate this one. The 1 comment I heard was fuel rail & EGR on how it works internally under the plenum. I may just live with it or if I can at least try another TB and just see if it completely illiminates this noise. It is so wierd to be able to vary the pitch with while accelatoring at about 1/4 to 1/2 throttle. Appreciate the input. I have seen little things missed before so another thought or set eyes sure helps.
Jim

A cracked or leaking EGR tube will give you a slight high pitch whistle. You can spray carb cleaner around the tube and valve to see if RPMs change. It may just be the sound of teh air going in to the TB. Are you running the stock air box or did you pull that for a different intake? The stock box tends to muffle that sound..

I did change out the entire stock box assembly & air cleaner, no change, yep we did spray carb cleaner to find leaks and no change either. Maybe I am being a little to picky for a 10 year old car. My 94, 95, 02 did not make that sound. I was thinking maybe the casting or some other imprefection on some of the 98 TBs may have small issues. I have the next couple of weeks off so I will check and see what else I can find. You help very much appreciated.

If you spray the carb cleaner around the outside of the TB, the UIM and the LIM listen for changes in RPM. If no change then you have no leak there either. Then there is no reason to replace the TB. It may just be the air entering the TB normally.

Yep we did all that too with no luck. Once I find out what is going with this thing I will post it or just live with it.

My 1998 Buick Lesabre stock n/a TB whistles at exactly 35% TPS, every single time. I think it'* a function of the throttle plate shape, which has kind of a wierd "lip" at the bottom. The */c guys have just a flat plate in their TB. When I installed a modded L67 TB, the whistle is gone.

Wife'* 2004 LeSabre n/a does not do this whistle. I can't recall if the TB plate has the lip.

I do not know if any other year n/a TB has this lip I speak of, but I know what you are going through.