Oooh. You actually put in a MAP sensor in place of the BARO sensor it seems. Which is ok, they're the same sensor. So no harm done. But no fixing either. I'm not sure where the BARO sensor is on the Montes, but apparently close to the VAC sensor. You didn't do anything to fix your issue. Your VAC sensor giving you the 34 code is still in there. So if it was bad, it's still bad. Because you didn't change it.
The VAC sensor on your car looks externally the same as the BARO sensor (I'm guessing that is it) you took off, except there's a vacuum line going to the port on the bottom of the sensor, where the other end connects to the intake manifold or carburetor. Not familiar enough with the Chevys to know off the top of my head exactly where the sensors are physically located. But they do use a VAC on the V8 only. MAP on the V6. Both use the MAP/BARO sesnor as a BARO sensor only. So V6's have 2 MAPS essentially, and the V8 cars have 1 VAC sensor connected to the intake manifold vacuum, and 1 MAP/BARO (used as BARO only).
Did you do any voltage checking to see if it's acting right?
If it is indeed a MAP/BARO sensor you bought, which is what it looks like, that's likely your problem. A MAP, or Manifold Absolute Pressure, works differently than the VAC sensors. If your sensor has a vacuum hose attached to the nipple, you need a differential pressure sensor. MAP and Diff Pressure Sensors have different voltages depending on the vacuum signal. Kinda backwards from each other. This is likely your issue. At least one of your issues. Never fear, your Baro sensor is new, at least! They're the same sensor, the MAP and BARO.
Read this post.
Caveat- this is mainly for Oldsmobile 307s, to which I'm more familiar with than say, the 305 Chevy engine. I believe since they use the same sensors, they work the same, but I have done absolutely no further research on them, thus, if you know something different, please correct me where I'm...
You need the right part number ACDelco or equivalent.
Here's one on ebay. On sale. The same part number that originally came on your car. AutoZone is out of their minds trying to pass off MAP sensor as a VAC sensor. Wonder how many people have lost their hair wasting their money on that thing instead of them getting the right sensor for their Monte SS? I will SPEND YOUR MONEY HERE. Do it. This one's cheap enough. They're getting more scarce as the days go by.
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And an FE1618 by Niehoff (Repackaged Borg Warner sensor). Says MAP on the box, but it is actually a VAC. You can still see the GM logo on the sensor. Hmm. Wonder who made them for GM, Borg Warner...
Find many great new & used options and get the best deals for Manifold Absolute Pressure Sensor-Differential Pressure Sensor Niehoff FE1618 at the best online prices at eBay! Free shipping for many products!
Rockauto.com has Diff Pressure Sensor too.