TVS?

You might try 'Thermal Vacuum Switch'  That is how TVS is defined in the 1989-90 Geo Prizm facotry manual.  By the way a 'TV' is a Throttle Valve.  What other kind of throttle is there? Bill Wildepad wrote: I've been having problems with a 1985 Old 5.0L (307) engine.

Fortunately, I finally found a book that lists the problem and gives a troubleshooting diagram.

More fortunately, I'd already performed all the tests the troubleshooter calls for (although not in that particular order).

It said to replace the TVS.

Unfortunately, it doesn't say what a TVS is, what it looks like, or where on the engine it can be found.

I tried googling for it, but all I can come up with is television sets (TVs instead of TVS).

Can anyone please enlighten me?

From what I remember, TVS is a "Thermal Vacuum Switch". On the older GM', they were mounted on the air filter housing and had a vacuum line running to it.....

Hope you find it!...

line running to it.....

Thanks for the info.

I did finally find it, but it has nothing to do with the problem -- all the TVS does on this engine is operate the heat riser.

Sigh! Back to the drawing board.

Thanks!

Complicating the problem was that the online parts stores don't call it that, their name for it is 'ported vacuum switch'.

But, sigh!, I finally traced it down, and found that couldn't be the problem -- it doesn't control anything on this engine except the heat riser, and my problem is that the rear vacuum break is shutting of vacuum to the choke pull-off until the engine is warm.

line running to it.....

I think you nailed this one.

From acronymfinder.com:

TVS Thermal Vacuum Switch (automotive)

Very handy site!

Rick

line running to it.....

:) Thanks for looking it up.

The unfortunate thing is that the repair manuals call it that, but the parts houses call it a 'ported vacuum switch' (I needed to find a picture of it so that I could recognize it on the engine.)

More unfortunately, it turned out the problem isn't that, and no one here seems to know anything about '85 Olds V8 engines, so I'm back to square one.

vacuum line running to it.....

No worries. That site has been greatly helpful to me in the past.

Man, that is a pickle you've got there. Wish I could help, but I'm by no means a mechanic.

Only thing I can think of is perhaps try posting in alt.autos.oldsmobile?

I know it's a long shot, but who knows?

Best of luck to you!

Rick

The sad part is that I was a pretty fair mechanic in my day, but it was on cars without electronic controls, pollution control devices, or any of that other clutter that's on this engine.

The strange thing is that I've managed a work-around, curing the symptom without knowing the cause. I just hope it doesn't come back to bite me.

I tried there. They suggested here. :)

Thanks!