My '92 305 TBI has around 100,000 miles and the butterflies have seemed to have worn "grooves" in their housings, that essentially allows them to rest slightly "deeper" in their bores than as new. I notice that when they move out of their "grooves" there is a hesitation, like the butterfly edges are experiencing increased friction until they emerge from their "groove", then they act as normal.

My goal is to remove the throttle hesitation I noted above. Can you give me any kind words...or is my throttle body basically history? Thanks. Dave

 

Not sure about your problem, but I think you mean TPI (tuned port injection) I could be wrong but I don't think the Throttle body injection (tbi) has any butterflies... any that you can see with the tb assmebled anyways.

 

Josh, thanks for the feedback. I'm positive I'm running a TBI, not TPI.

Perhaps the confusion arises because I wanted to use the term butterflies rather than "throttle blades or plates", which is the way my butterflies are referred to in one of your tech articles. Sometimes authors try to create a bit more interest in the topic, as in this case, rather than saying "there's a throttle blade in my throttle body".

Anyway, I'll try to be more precise in the future. Thanks again.

 

Don't worry about the terminology on that dave. Butterflies, throttle plates, throttle valves, it's the same thing regardless of whether it's a TBI, TPI, or carburated. Have you tried to manually move them by hand to see if they might be catching on the lip a little.

 

Well I've activated the throttle linkage by hand, which moves the butterflies. Indeed, they are catching on the lip of what I've described as the new groove.

Your question made me wonder about a more basic question...I have assumed the walls of the bore should be perfectly smooth and that what I'm seeing as a worn groove in the wall is bad. Is it possible the groove is really the butterflies' actual designed resting point?

Anyway, I still have that hesitation that can't be right. I'd say yes they're catching on the edge, but more accurately they appear to be fairly tightly seated at rest and when I activate them they hestitate for a split second, then "pop" out.

I'll check for further input tonight. Thanks again. Dave

 

I gotcha, i wasn't going out of my way to make you sound like an *** or anything, its just when i hear butterflies i think of the tpi throttle body, i've owned a tbi car for a long time and never really thought of it as having butterflies, even though it does have the plates ect.. Anyways, sorry for the confusion, my bad.

 

Following up on my original thread...

"I have assumed the walls of the throttle bore should be perfectly smooth and that what I'm calling a worn groove in the wall is bad. Is it possible the "groove" is really the butterflies' actual as-designed resting point?"

Is it possible to adjust the resting position of the butterflies? In my case, if they could be adjusted to a "pre-load" state, where they wouldn't rest so deeply in the bore, I could eliminate my throttle hesitation.

Would that re-positioning be compensated for by the ECM and not affect the idle speed?

Or should I just find a new TBI and start over?

Thanks. Dave

 

that or have your current tbi unit bored. that will solve the problem and give you a lil performance boost.

 

TBI's have bearings so yo don't have shaft problems, so the butterfly shouldnt hit the bore under normal use, try idling it up a 1/4 turn at a time and it should smooth out.....

 

jbbiggs suggested: "try idling it up a 1/4 turn at a time and it should smooth out....."

I guess I misunderstood my shop manual...I thought there was no manual idle adjustment possible with a tbi...the "ECM" would just take care of it automatically.

Could you clarify where to find the adjuster? Thanks. Dave

 

If you look at the front of the throttle body on the right side you should see either a hole with a torx screw that you idle it up with. If you do not see this there is probably a thin metal removable plug over it, I use a sharp object to punch a hole in this then pry it out to gain acess to the screw.

Hope this helps.....