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My car needs a "smoke test"

First off, let me just say that I know absolutely nothing about cars. So feel free to speak to me like an idiot.

Moving on, I drive a 2004 Crown Vic with almost 92,000 miles on it. I recently purchased it from a private seller around a month ago. The Check Engine light came on just today, so I went to a local service center where they told me there’s something wrong with the fuel tank (either the pressure or the voltage? I feel like an idiot for forgetting exactly what he said, and he didn’t put it on the invoice… just that my car would need a “smoke test”). Now, they’re going to charge around $95 for the smoke test (minus the $45 for the check engine diagnostic they did)… he was a little vague on what the cost would be for the repair (I guessed because he was unsure about what the problem exactly was). What do you think am I looking at price-wise? And do you think it’d be safe for me to continue driving it until I can get it fixed? (He couldn’t do the test/repair regardless until Monday.)

Thank you so much for your time in reading. I greatly appreciate any and all responses.

The problem is related to your fuel tank venting and purging…Sometimes it’s just a loose or defective gas cap…If you do not need an emissions TEST then this is not a serious issue that effects the safety or performance of your car…Your car is drivable.

No, he said the engine light’s code definitely had something to do with the fuel tank, and that the smoke test was required… that is, if I wanted the check engine light to go away and be sure nothing is wrong.

Did they write the exact error code on the invoice? (Would look like “P1234” - I’m taking a wild guess that yours is P0442).

The only thing that would bring on a smoke test is exactly what Caddyman said - an issue having to do with fuel tank venting. Fuel evaporates - creates a lot of fumes. Today’s car’s keep the fumes in an “evaporative emissions system.” Its a series of tubes that capture the fumes from the tank and send them to a canister in the front of the car, and then send them to the engine to be burned.

In other words, your fuel system is supposed to be totally closed to the atmosphere. The car “tests” it once in a while to see if its closed. If the series of evap tubes won’t hold a vacuum then it will set an error code because there is a leak someplace. A small leak code is P0442.

The hard part is finding the small leak - thus a smoke test.

However, one of the most common reasons a P0442 gets set is because of a gas cap that doesn’t deal completely - as Caddyman said.

I’ve twisted that thing so tight that I don’t think it could be responsible, but then again, maybe it is… I mean, it doesn’t “click” like it says it should (“Twist cap until it clicks or check engine light may turn on” is right on the cap), so I have to go based on my own strength—thus, when I can’t twist it any further, I declare it sealed. Is this something that they would normally check or should I bring it up when I go back Monday afternoon? Further, should I do anything myself or ask any particular questions? I was considering calling them back before the night’s over, but I’m not so sure what on earth to ask. I mean, I want to get a solid price on what the repair would be.

No, he didn’t state the error code on the invoice. I found that odd, but then again I could have asked many more questions than I did there. Even if there is a leak, though, the car will be fine to drive until it’s fixed?

Thanks Cig. On a Vic, the EVAP canister and much of the plumbing are mounted on the center of the trunk well, under the car, easy to inspect for damage…It’s not a safety issue…You can slide under the back of your car, look up at the bottom of the trunk and there it is. You can reset the dash light by disconnecting a battery cable for 30 seconds…But this will erase any stored trouble codes…Any parts store will read the codes for you for free…Then post the code back here…

I called the mechanic and he told me it wasn’t the EVAP code, it was an FTP sensor reporting an irregular voltage… He didn’t say there was a code, however.

EDIT: Basically, he’s not telling me a figure about what the cost will be, so I wanted to know a ballpark figure of what I could be looking at… second, I was wondering if it were safe to drive.

The mechanic can’t tell you what it’s going to cost until the smoke test shows results. That is why he is hesitant to provide an additional estimate. Get the test done and have him call you to discuss results and costs.

I think we all agree it is safe to drive until you have the smoke test done, or if you choose the get the codes read free at a participating auto store and post back here to see if anyone has any additional info or guidance.

I think you should have the test done and the repair made soon. You never know when the CEL will come on and it will be a more serious issue if you don’t have this one fixed.

369, you are being set up for a four figure repair bill when there is nothing of any importance wrong with your car…If there is something seriously wrong with your car, you will know about it without the CEL complaining about some emissions problem, real or imaginary…

“It uses this sensor, also known as a fuel tank pressure (FTP) sensor to check for leaks. Basically P0453 means the PCM (Powertrain Control Module) noticed the EVAP Pressure sensor or FTP is indicating a higher than normal pressure (above 4.5 Volts) in the EVAP system. NOTE: On some vehicles the FTP is a part of the fuel pump assembly in the tank.”

Ask them to explain how a smoke test is going to help - because I doubt that it will. But if you report the specific code people could say more. If it is P0453, as Caddyman suggests, then the first thing to check is the sensor’s wiring.

IF, in fact, there is an actual evap system problem, it will be a system blockage - not a leak. In a smoke test you just pump smoke into the lines and look for where it escapes. If there’s a blockage, there will be no escape.

What kind of a shop did you bring it to.

cigroller-- The mechanic I brought it to (it was a local Mobil, by the way) told me that he could have checked the voltage with a different test, but that it was far more likely to be a leak—thus advising the smoke test instead of doing both. Is there something you would advise I do differently?

jayhawkroy-- Thank you for your input.

jtsanders-- That was my thought, indeed. I’m not necessarily looking to ignore any problem with my car, but I’m a complete idiot with vehicles so I felt like getting more information as I went along. Thanks for your input, however.

“369, you are being set up for a four figure repair bill when there is nothing of any importance wrong with your car”
– What exactly do you mean here? And, as I asked cigroller, what would you do in my situation?

Thank you all again for your responses.

Without the exact code, I can’t really advise you about it. Like I said, if its a P0453 code then there is no leak - there is a blockage. P0453 would happen with too much pressure in the tank. A leak would mean it can’t hold pressure.

So get the code, and then there is something to talk about.

“-- What exactly do you mean here?” I mean your car will operate perfectly without you doing ANYTHING…Emissions nag lights that do not not effect the drivability of the car can be ignored (in my humble opinion)…

The first thing I would do would be to replace the gas cap with a FACTORY new one, purchased at a Ford dealer…Then I would put the car up on a lift and INSPECT the EVAP control module and it’s connecting hoses which are plainly visible underneath the trunk…The hoses are somewhat vulnerable to damage in this location and it requires no smoke test to spot damage…

I think a little explanation is in order here. Terminology can be tricky and misleading if you’re not well versed in it.

The EPA requires that everything related to your fuel system be design such that no gasoline can evaporate into the atmosphere. To accomplish this, manufacturers have designed in a vapor recovery system, commonly called am EVAP system or evaporative emissions system. One of the concepts under which the system operates is that it maintains a slight vacuum in the gas tank and all of its associated hardware, the vacuum preventing the escape of fumes. If you have a leak, it prevents the vacuum from being maintained and a sensor trips the Check Engine Light.

The smoke test is one wherein smoke is pumped into the air spaces in your gas tank and fuel system, and the smoke will be forceed out the leak, telling the shop where it is. It’s impossible for them to quote a repair price until they see where the leak is.

The “codes” would provide a bit more information. EVAP system codes run from 0440 to 0455, and the exact one helps isolate the possible problem.

As others have said, your vehicle will operate fine with the tank vented to atmosphere (a leak in the EVAP system). Driving the car as is will cause no damage to the vehicle and is completely safe. However, as others have mentioned, it effectively renders your Chel Engine Light useless as a “heads up” should you develo some problem that CAN cause damage. I strongly advise against not getting this fixed.

I’d suggest first getting an OEM cap and seeing of the light goes out. If it does not, have the smoke test and at least find out what needs repairing. It may be something fairly low in cost.

Well, here’s some news…

They ran the smoke test, found that there was not a leak but that the hose was damaged. They’re going to replace that, guarantee their work for a year (or 12,000 miles), and the magic number is $425…

Tell me just one thing: Did I just get ripped off?

(Also, to mountainbike, thank you for explaining some history and detail. I appreciate it.)

I don’t think so. The hose might not be too expensive, but changing it often requires some work. And you’re also paying for the test as well as their experrtise, facilities, and equipment.

I can remember when $425 was an expensive repair. That was long, long ago…

Happy motoring.

Thank you very much. I’ll be sure to frequent this board more often. You guys are very knowledgeable and aren’t condescending at all.

You’re very welcome. Most of us here understand that we all contain knowledge and we all contain ignorance, it just varies from person to person. I’m good with a wrench or a design drawing, but when it comes to finance, human relations, or whatever your area of expertise is, I’m probably terrible!

Everyone can’t know about cars. We need people to know all about that other stuff in life too. The stuff we don’t know much about.

Happy motoring.

What was the nature of the damage to the hose and what was the code?

We’re still left with a mystery of what - exactly - was wrong.