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Discussion Starter · #1 ·
My Car: 2000 Ford Taurus, 3.0L Flex Fuel, OHV, 89k miles
I have misfire code P0302 and smog pump code P0411. Possible causes for both include vacuum leak. I want to determine if I have a vacuum leak, so I can repair it. Finding it will come later, IF I have a vacuum leak. After I do this, I plan on doing a compression test next, if needed. But first...vacuum test!

Short Version of Question:
How can I get clear, specific instructions on how to do a vacuum test using a vacuum gauge on my car?

Long Version of Question:
I can't seem to find instructions anywhere. I "borrowed" a vacuum gauge from Autozone which has no instruction manual. I borrowed it by leaving a deposit in the amount of purchase price, and if I return it, I get the deposit back. It has a hand squeeze grip. It has only a rubber hose and I had to buy some connections, for about $3. The hose on gauge does seem to be a little loose, so I did buy a one foot section of additional hose myself. Should I use a hose clamp or something anywhere when testing to ensure a tight seal?

YouTube has some videos on how to do this. Problems/differences are 1) in video there is no hand grip on gauge. Will this gauge work? 2) they don't show WHERE to connect vacuum gauge, or 3) if they do show where, it is not a Taurus, and 4) they don't show HOW to connect gauge.

If this vacuum gauge from Autozone is not right, am I better off buying one, and if so, what brand, what type, and how much? How often can I expect to use it, really? I mean, I've been a driver for nearly 30 years and NEVER used one before...

Instructions on the web say "connect to vacuum port" and the more specific ones say "the vacuum port is on the intake manifold after the throttle body." OK...there are 2 of those on my Taurus. One is right after the throttle body, driver side, and is connected to a large black rubber vacuum hose that goes down and to the passenger side of engine. The other vacuum port is on passenger side and the vacuum connector has more than one smaller hard plastic vacuum tubes in the rubber connector. Which one do I connect to? Apparently I can connect to anything to test for vacuum or lack of it....more questions on that later...

When I connect, do I connect to manifold only, to disconnected hose only, or do I use a "T" to connect it as normal, but having the gauge in as part of the system?

With DTC codes listed above, which vacuum hose or hoses should I test as main suspects of problem? Should I test all vacuum hoses as just good practice in preventative maintenance? If I check ALL vacuum lines, is there a list of them so I can check them off a list to be thorough?

The black hose mentioned above, on driver's side, has some chemical breakdown to it and leaves lots of smudgy reside on my hands whenever I touch it. I am halfway inclined to spend the $5 or less it will take to just replace it. It's about 18 inches long or less.

If one of the red hard plastic vacuum tubes is the culprit, what's the best way to repair? I know I'm getting ahead of myself as I have not yet found where it's leaking, or even really confirmed that there is a vacuum leak at all...but knowing where I'm going, even a taste, might be good.

Experienced guys may laugh at this, as they take it for granted. But I have literally spent hours on the web today. I know what the results mean (fluctuating needle, etc.), that's easy to find. But how to connect the damn thing? This basic thing seems a total mystery and not explained anywhere I've looked. I've never done a vacuum test before, so this is new territory for me.

Any web video (Taurus) or specific instructions on web with a link (Taurus), or written instructions in response, would be greatly appreciated!

Mark in LA, CA
 

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A vac gauge is not the best way to look for vacuum leaks in the first place. A gauge will only show gross leaks that you could probably hear hissing without any gauge in the first place.

First thing to do is visually inspect every vac line and the PCV lines for cracks, breaks, splits, soft spots, etc. Careful inspection can often find even a small leak in a line. If the leak isnt in a line, but an intake gasket, you can spray brake cleaner, etc around suspected leak areas and listen for small changes in how the engine runs before the IAC corrects idle speed back to target values.

BEST way is to get a scan tool that can monitor short and long term fuel trims. Positive long trims over a few % positive can alert you to a leak, and if the leak effects both cylinder banks or just one (unbalanced trims between banks), and tell you which bank has the leak. A leak that effects both banks is likely a vac line leak or PCV system leak, while a leak that effects only one bank is typically an intake gasket problem. To narrow down the leak location, spraying brake cleaner, etc around the suspect areas while watching short fuel trims (will jump negative when the leak sucks in the spray).
 

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I fear you may be on the wrong track already, neither of those codes suggests a vacuum leak. (Although it is a likely problem on a 10 year old Taurus). Forget the air pump code for a second, that's more likely to be an electrical problem with the air injection system.

Nylon vacuum lines are very sturdy, I wouldnt worry too much about them. Feel free to replace any rotting rubber hoses. The one you feel on top of the motor is probably a PCV hose. There is another that is usually the culprit of vacuum leaks on Taurus motors and is (of course) harder to access under the intake.

A specific cylinder misfire code means that cylinder has failed a power balance test, which is run occasionally by the powertrain computer. It's most likely a spark or fuel problem at this point. Does your Taurus have coil on plug?
 

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Discussion Starter · #4 ·
My coil and plugs are separate from each other. I have standard plugs with plug wires that attach to a coil. Plug on one end, coil on the other end, of the plug wires.

Did a tune up a while back, new plugs, new wires, and a used coil. Misfire is still there on Cyl 2.

Many sources indicate vacuum leak is a possibility and a cheap thing to check, which is why I wanted to start there.

The nylon vacuum tubes are tough, you indicate. But on my car, more than one has been patched...using black hose to splice the nylon pieces together. Work done by previous owner, not me. But that indicates to me that it may be leaking...so I thought a vacuum test would be a good start.

If vacuum has no leaks or does not fix the problem, next step is compression test, which I plan to do this weekend. Wanted to figure out the vacuum test this week before this weekend if I could.
 

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Discussion Starter · #6 ·
Cheaper than a new one. Ford dealership wanted over $200 for a new one. The used one did improve how the engine runs...but misfire is still there, so I suspect the misfire is not the coil.
 

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It's just very unlikely that a vac leak will cause a misfire on 1 cylinder, an entire bank yes, but on an intake with a common EGR port it's very unlikely to make just one cylinder misfire. Honestly one of the easier ways to check for vac leaks is to spray soapy water around all suspected areas, and looks for bubbles. The next easiest way, IMO, on a 7 year old car is to just start taking apart the intake and replacing all your upper & lower intake gaskets, suspect PCV elbows & hoses, etc. I find more vacuum leaks by eye and hand than any other method.
 

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Discussion Starter · #8 ·
Well the vacuum test failed. I learned how to do it with more internet browsing. YES you need to use a "T" and tie in to the line and still have it function. I tried both vacuum lines on the intake manifold, and both gave the same results.

From the pictures in the Haynes manual, I am having a compression failure. It says to confirm with a compression test.

I did that, and cyl # 2 failed. Most were in the 160-165 range, and cyl #2 was only 90. Did it dry and wet, and a little oil in cyl made no difference on any, so I can rule out a piston ring. Bottom end is fine, top end needs something.

Next is a leak down test or just do a valve job...that would be another post.
 

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BEST way is to get a scan tool that can monitor short and long term fuel trims. Positive long trims over a few % positive can alert you to a leak, and if the leak effects both cylinder banks or just one (unbalanced trims between banks), and tell you which bank has the leak. A leak that effects both banks is likely a vac line leak or PCV system leak, while a leak that effects only one bank is typically an intake gasket problem. To narrow down the leak location, spraying brake cleaner, etc around the suspect areas while watching short fuel trims (will jump negative when the leak sucks in the spray).
Where's the best place to purhase one of these Scan Tools? Any body know approximate cost?

thanks
 

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Regarding scan tools,
Actron makes scanners that can read fuel trim. Actron®
You need to buy one from the Scan Tools group. Others appear to be code readers. INNOVA (sp) also makes scanners. Make sure the unit can handle CAN bus (not just OBDII codes).

A better performance per buck is PC-based. You buy a plug-in (goes between the OBDII port and PC) and software (for the PC). OBDLINK is one. AutoEnginuity is another. There are smart phone-based ones, too.
 

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Regarding scan tools,
Actron makes scanners that can read fuel trim. Actron®
You need to buy one from the Scan Tools group. Others appear to be code readers. INNOVA (sp) also makes scanners. Make sure the unit can handle CAN bus (not just OBDII codes).

A better performance per buck is PC-based. You buy a plug-in (goes between the OBDII port and PC) and software (for the PC). OBDLINK is one. AutoEnginuity is another. There are smart phone-based ones, too.
I have been happy with my CarChip which recordes things like fuel trim, temp, volts, and on and on up to 300 driving hours, as well as speed, accel, and braking. If a code is set, you can see when it happened, and what was going on at the time. Also record of miles, dates and such.

-chart-
 

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That is a significant drop in compression. I'm wondering if it could be a leaking head gasket?
Also, you mentioned that a few vacuum lines have been spliced together - I would replace all lines that you see as "cobbled" together by the PO. Also, make sure you inspect your PCV line as others have said. Very common failure point. Actually, I would suggest replacing it because if it's not causing a vacuum leak now, it will shortly.
Good luck and keep us posted.
 
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