Getting intermittent bogging in my 88 GTA 5.7 TPI.

I started looking around at the vacuum hoses. Some are sort of 'rotting', not with actual holes in them, but sort of decomposing, black dust comes off on your fingers, and they feel very rough. Can't see any actual holes. Some of the hoses disappear under parts of the engine so you can't even look at them easily.

Any suggestions for where to look for vac leaks?

Oh, and some rodent has chewed on an injector wire already, so maybe they have been eating the vac hoses, too, but haven't found anything yet.

Thanks

 

I'd replace them all one by one. Don't forget to check the "Orb Vacuum Ball" in the drivers fender.

 

 

You can also use a hand held propane torch. Take the burner nozzle off and put some soft rubber hose over the end of the tube. With the engine running, turn on the propane and move the hose around the fittings and along the intake manifold.

Same result as above. If the idle goes up, you've located where the propane is being sucked into the intake. With a rubber hose, it's easier to move it around to help pinpoint a suction leak. Just keep the hose away from the carb/TB inlet which shouldn't be a problem with a TPI system. Propane is heavier than air so it sinks. Do the test outside or in a well ventilated area. It's not like the bottle needs to be turned wide open.

 

I used starter fluid to find my leaks.

 

Smoke machines work also. Even cheap ones from ebay lol

 

Where did you guys find the vacuum leaks?

Thanks

 

Over the years, I've found vacuum leaks all over the place. Cracked vacuum hose elbows, intake manifold gaskets, carb base plate gaskets. I've heard of people even finding bad brake boosters causing a leak.

 

The AC controls.

 

All of the above. All good approaches, true facts.

Vacuum leaks are notoriously hard to find. For one thing, when it leaks out, it's real hard to see; it's clear. You gotta get a special piece of shop equipment to clean it up, called a "vacuum cleaner".

Oh well, enough of that... if you have brittle crumbling hoses, that's the place to start. You can go to almost any parts store and find that hard plastic line and the fittings for it hanging on cards, usually near the PCV stuff and oil drain plugs. You don't "have to" replace it with the same size necessarily, just get as close as you can, by finding fittings that work where you need them (90° vs straight and such as that) and then just use whatever size line fits the fittings you find. You can even use regular rubber hose for most of them.

Then once you've got the obvious and eeeezy stuff out in the open where you can see it and work on it, go to work on the rest.

Accessory things like cruise and AC, you can disconnect the feed from the engine and cap the nipple, and see if it makes any difference to how the engine runs. You can drive it around for a bit without that for troubleshooting purposes. The brake booster, if you hear a "sssssspppplooooooooossssshhh" noise when you push the brakes, it's effed up; just change out the booster and the MC as an assembly since more than likely you have a brake fluid leak you just don't know about yet and that's what killed the booster.