I suspect a vacuum leak somewhere, but I don't know where is best to test, or what numbers are for what lines.

I'm used to diesels with less vacuum lines.

Thanks

 

Here is what I have.

What is a CCV valve??

 

'CCV' is the crankcase vent valve - basically just the fresh air intake side of the PCV system. You'll notice the PCV valve is in the opposite valve cover. The PCV sucks the fumes out of the engine, and the fresh air that comes in to replace it comes through the CCV valve.

The place to test engine vacuum is the intake manifold - it has to be somewhere thats exposed to vacuum all the time (manifold vacuum) when the engine is running, so nothing in the throttle body for TBI/TPI, and nothing above the carb base if using a carb.

The spot where the power brake hose is hooked up is a good spot, if your guage can be fitted up to a 3/8" port. The hose for the heater/AC controls would be good too ('To HVAC' on your label) and should have a smaller fitting.

 

Ok thanks. So the CCV is not just an upside down PCV(2 different valves?)?? Should I replace it at the same time as the PVC?

Also, what vacuum values am I looking for? Should all the hoses have the same value, so if I find a hose with a lower value I can pinpoint the leak? Or are they all designed to have different value? Do they all connect to a master fitting on the intake, or are there multiple?

Since you say anything connected to the throttle body is bad, then the TOP fitting won't do?

Basically I'm having a little lope at idle, cruise control doesn't work, and performace is a little "jerky". Thinking vacuum is a good place to start since the car sat for a long time and some of the lines look like they have little chunks taken out.

I'm finding my vaccum diagram is a little vague for me and I see other lines(maybe AIR?) that aren't on the diagram.

 

CCV isn't really a valve, its basically just an open plastic tube with a hose attatched. Unless its visibly broken or plugged for some reason, theres no reason to replace it.

Normal vacuum for a given engine will vary, depending on condition, age, mileage, etc etc.. but I'd imagine normal for an engine like yours, if all stock, would be between 17"-20" at idle in P or N warmed up. If its above 15" and is fairly steady on the guage, then your probably OK as far as what you can deduce from a vacuum guage.

What you should do to check for a vacuum leak is to spray some brake cleaner right where the intake manifold meets up to the cylinder heads, and see if engine RPM or how it runs changes. You'll want to do this almost anywhere theres a gasket on the TPI intake - back of the TB, top and bottom of the runners, and where the lower manifold meets the heads.

If you find a spot where spraying brake cleaner did seem to make a noticeable difference in running conditions, then you have probably found a problem spot.

Another thing to check, is your ignition timing - make sure its correct, and the distributor clamp is tight. There is a certain procedure for this on an EFI car like yours, though I can't remember it off-hand. Its not difficult, but been too long since I have done it lol.

Anyway... if the base timing has changed for one reason or another, it could make it run rough/lopey/jerky as you described. Shouldn't cause any problems with cruise control, but a vacuum leak could.

 

Ok thanks for the responses. I tested a few locations and got about 22" at cold idle. I haven't checked every hose yet tho.

I'm curious about the brake cleaner method....how does that acually work? Is brake cleaner ok to get in the engine??

Thanks again

 

The brake cleaner acts like fuel if it gets sucked into the intake which it would if you sprayed on something with a vacuum leak. It will be fine in the motor, it just burns like gas.

 

Cool, good to know. Thanks for that

 

You'll notice 'something' going on if you spray it onto a leak spot - you know how you put soapy water over the fittings on you gas BBQ to check for leaks? Similar idea, though it would leak in reverse... it would suck the stuff into the motor, not make bubbles as it tries to escape. Usually you'll notice the idle speed change slightly for a moment (as the fluid momentarily plugged the leak and gave the motor a little extra fuel). If it does, theres your leak.