MALIBU Vacuum/Defrost

[Dezimade]

Hey guys! I need to address the acceleration when I put my defrost on.
Can someone lead me in a direction to address this ? As ever thing heat, is new.
I have been told that it’s my vacuum.
I need enlightenment. Thanks. Dez

 

[Ribbedroof]

OE shop manual which is available either used on eBay or digitally all over the place is an excellent source for these issues. Usually includes a troubleshooting flow chart. But briefly yes your vacuum reservoir does not hold enough vacuum therefore when vacuum falls as the throttle plates are opened ,the actuator door canister defaults to defrost by design

 

[Dezimade]

OE shop manual which is available either used on eBay or digitally all over the place is an excellent source for these issues. Usually includes a troubleshooting flow chart. But briefly yes your vacuum reservoir does not hold enough vacuum therefore when vacuum falls as the throttle plates are opened ,the actuator door canister defaults to defrost by design

Imagine if you’re talking to a beginner and say that again. Lol 😆

 

[78Delta88]

Mitchell . com. Mitchell DIY you can pay by month or year. This gives you everything for that specific year, make, model.

Look for a thin vacuum line near the blower motor on the passenger side cowl. This line feed the switch and actuators for the HVAC system pieces under and behind the dash.

If this line breaks or becomes disconnected the HVAC door motor defaults to defrost. This is a safety feature built in so that if vacuum lost and you select heat it will only send hot air upward to the windshield to keep it defrosted/defogged.

This line connects to the spaghetti noodle mess of vacuum lines on the engine.

If this tiny little line leak is causing acceleration issues, you have bigger issues elsewhere.

 

[78Delta88]

Likewise, as stated above manuals are available for your specific vehicle on eBay or local parts store. Most everyone carries Haynes manual, and if they don't have, they should be able to order.

 

[Dezimade]

Mitchell . com. Mitchell DIY you can pay by month or year. This gives you everything for that specific year, make, model.

Look for a thin vacuum line near the blower motor on the passenger side cowl. This line feed the switch and actuators for the HVAC system pieces under and behind the dash.

If this line breaks or becomes disconnected the HVAC door motor defaults to defrost. This is a safety feature built in so that if vacuum lost and you select heat it will only send hot air upward to the windshield to keep it defrosted/defogged.

This line connects to the spaghetti noodle mess of vacuum lines on the engine.

If this tiny little line leak is causing acceleration issues, you have bigger issues elsewhere.

Great info. I will get that info thanks so much!! Now can you kinda explain what BIGGER issues may lead me ? 😳 Dez

 

[78Delta88]

You need to find out why such a small leak is causing a stumble on acceleration.

You have a bigger leak somewhere that is throwing off your air/fuel mix. Leak is causing a lean issue.

 

[Ribbedroof]

Forget the Haynes and Chilton manuals. You want the GM factory shop manual. It will include MUCH MUCH more useful information about pretty much every subsystem on the car. This is the GM manual for 1988 Monte Carlo/Full size.

A Chilton or haynes manual is less than half as thick, and covers every Chevelle year ever made. Contains only the most basic information. You WANT the GM manual. I paid $14 for this one on ebay a month ago. It can be bought new on CD for more...I prefer having the actual paper book, but some people like being able to print the pages they need for a given task.

 

[78Delta88]

Exactly, and Also good reason to look at Mitchell.

Once you sign up you get everything they have available for that specific make, model and year. This includes (usually) diagrams, schematics, recall info, technical information sheets sent out by manufacturer, along with PDF of the manual for your specific vehicle.

If you can find the OEM manual on ebay, even better.

You have to do your own homework, but the info is there, you just might have to dig a bit.

 

[Ribbedroof]

Here are the pertinent pages from the 88 shop manual, which is pretty much the same system as all G bodies OTHER THAN the automatic A/C system found in higher option carlines (I think Buick and Olds...never seen one in real life)