Service engine soon light

My wife's care is a Mitsubishi Lancer 2002. The "service engine soon"
light came on a few weeks ago. I tightened the gas cap and the light
went off. Since then the light comes on after I have put in some gas.
I tighten the cap and the light goes out after 2 or 3 starts. It now
went on several days after I put some gas into the tank. Is it possible
to have a defective gas cap? It looks fine to me but I don't know what
to look for.

If the gas cap can be bad is it OK to get a gas cap from an auto store
or is it recommended one buys one from the dealer...the nearest one
being about 60 miles away.

Thanks in advance for any advice and expertise you can provide.

Salad > wrote:
>My wife's care is a Mitsubishi Lancer 2002. The "service engine soon"
>light came on a few weeks ago. I tightened the gas cap and the light
>went off. Since then the light comes on after I have put in some gas.
>I tighten the cap and the light goes out after 2 or 3 starts. It now
>went on several days after I put some gas into the tank. Is it possible
>to have a defective gas cap? It looks fine to me but I don't know what
>to look for.

That light means that the computer has recorded an error. That error
may or may not have anything to do with the gas cap. You need to get
a scanner and find out what the error is, because until you know what
the error code is, you have no idea what caused it or what the problem
relates to.

>If the gas cap can be bad is it OK to get a gas cap from an auto store
>or is it recommended one buys one from the dealer...the nearest one
>being about 60 miles away.

There are millions of things that can cause different errors, so I do
not know why you are fixated on the gas cap. If the gas cap does not
appear damaged and is sealing properly, there is no reason to replace it.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

Scott Dorsey wrote:
> Salad > wrote:
>
>>My wife's care is a Mitsubishi Lancer 2002. The "service engine soon"
>>light came on a few weeks ago. I tightened the gas cap and the light
>>went off. Since then the light comes on after I have put in some gas.
>>I tighten the cap and the light goes out after 2 or 3 starts. It now
>>went on several days after I put some gas into the tank. Is it possible
>>to have a defective gas cap? It looks fine to me but I don't know what
>>to look for.
>
>
> That light means that the computer has recorded an error. That error
> may or may not have anything to do with the gas cap. You need to get
> a scanner and find out what the error is, because until you know what
> the error code is, you have no idea what caused it or what the problem
> relates to.
>
>
>>If the gas cap can be bad is it OK to get a gas cap from an auto store
>>or is it recommended one buys one from the dealer...the nearest one
>>being about 60 miles away.
>
>
> There are millions of things that can cause different errors, so I do
> not know why you are fixated on the gas cap. If the gas cap does not
> appear damaged and is sealing properly, there is no reason to replace it.

It seemed odd that the service light goes off when I tighten the cap.
If the "service engine soon" light is "off" will a computer scan find
the problem? I guess that's my major question.

> --scott

Salad wrote:
> Scott Dorsey wrote:
>> Salad > wrote:
>>
>>> My wife's care is a Mitsubishi Lancer 2002. The "service engine
>>> soon" light came on a few weeks ago. I tightened the gas cap and the
>>> light went off. Since then the light comes on after I have put in
>>> some gas. I tighten the cap and the light goes out after 2 or 3
>>> starts. It now went on several days after I put some gas into the
>>> tank. Is it possible to have a defective gas cap? It looks fine to
>>> me but I don't know what to look for.
>>
>>
>> That light means that the computer has recorded an error. That error
>> may or may not have anything to do with the gas cap. You need to get
>> a scanner and find out what the error is, because until you know what
>> the error code is, you have no idea what caused it or what the problem
>> relates to.
>>
>>
>>> If the gas cap can be bad is it OK to get a gas cap from an auto
>>> store or is it recommended one buys one from the dealer...the nearest
>>> one being about 60 miles away.
>>
>>
>> There are millions of things that can cause different errors, so I do
>> not know why you are fixated on the gas cap. If the gas cap does not
>> appear damaged and is sealing properly, there is no reason to replace it.
>
> It seemed odd that the service light goes off when I tighten the cap. If
> the "service engine soon" light is "off" will a computer scan find the
> problem? I guess that's my major question.
>
>> --scott

Depends what the code was.

Salad > wrote:
>
>It seemed odd that the service light goes off when I tighten the cap.
>If the "service engine soon" light is "off" will a computer scan find
>the problem? I guess that's my major question.

Depends on what the code is and what kind of scanner you have access to.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

> Salad > wrote:
> >My wife's care is a Mitsubishi Lancer 2002. The "service engine soon"
> >light came on a few weeks ago. I tightened the gas cap and the light
> >went off. Since then the light comes on after I have put in some gas.
> >I tighten the cap and the light goes out after 2 or 3 starts. It now
> >went on several days after I put some gas into the tank. . . .

"Scott Dorsey" > wrote in message
...

> There are millions of things that can cause different errors, so I do
> not know why you are fixated on the gas cap.

This omits:
1. Modern dashboard indicators (e.g. gas cap open, door open)
merely multiply the number of things that will eventually malfunction,
sooner or later . . .
2. Interconnection of indicators for "Gas Uncapped" and "Service
Engine" may be standard in many brands. They are so in the
Ford Focus, where malfunction is common enough to get a
mention in the owner's manual, not to mention Ford trouble
newsgroups. I have seen this in my Focus 3 or 4 times, ignored
it each time, it eventually vanished, and there were no engine
problems . . .

--
Don Phillipson
Carlsbad Springs
(Ottawa, Canada)

Salad wrote:
> My wife's care is a Mitsubishi Lancer 2002. The "service engine soon"
> light came on a few weeks ago. I tightened the gas cap and the light
> went off. Since then the light comes on after I have put in some gas. I
> tighten the cap and the light goes out after 2 or 3 starts. It now went
> on several days after I put some gas into the tank. Is it possible to
> have a defective gas cap?

Absolutely, which is why a gas cap pressure test is part of an emissions
check.

> It looks fine to me but I don't know what to
> look for.

It could either be a broken or shrunkenseal around the threaded part of
the cap, or it could be a broken pressure/vacuum relief mechanism inside
the cap itself. You couldn't see the latter, and might not see the
former if the seal is simply hardened and shrunken a little.

> If the gas cap can be bad is it OK to get a gas cap from an auto store
> or is it recommended one buys one from the dealer...the nearest one
> being about 60 miles away.

I sure wouldn't go to a dealer$hip for that kind of part, provided that
my local auto parts store carries a direct replacement. Don't get some
generic part, get one specific to your make and model of car. Unless its
a limited-production exotic, which a Mitsubishi isn't, any auto parts
store should be able to get the correct cap if they don't already have
it on the shelf.

Salad wrote:

> It seemed odd that the service light goes off when I tighten the cap. If
> the "service engine soon" light is "off" will a computer scan find the
> problem? I guess that's my major question.
>

Usually you can tell that a code has been set and then cleared. Others,
such as various sensors out of range, can't be cleared except by a code
scan tool. The tool will also show you "impending" codes, which means
that the engine computer has detected an error, but it hasn't detected
it enough times to set the CEL. The computer does have logic in it to
throw away the occasional erroneous reading.

Steve wrote:

> Salad wrote:
>
>> My wife's care is a Mitsubishi Lancer 2002. The "service engine soon"
>> light came on a few weeks ago. I tightened the gas cap and the light
>> went off. Since then the light comes on after I have put in some gas.
>> I tighten the cap and the light goes out after 2 or 3 starts. It now
>> went on several days after I put some gas into the tank. Is it
>> possible to have a defective gas cap?
>
>
> Absolutely, which is why a gas cap pressure test is part of an emissions
> check.

LOL. I was wondering why my light went on yesterday after filling up
the gas a few days earlier. It hit me this morning, I went for the CA
smog check yesterday and was driving back home when the light came on.
The tech would have checked to see if I had modified the line I insert
the gas nozzle in. I tightened the gas cap again and the light went out.

>
>> It looks fine to me but I don't know what to look for.
>
> It could either be a broken or shrunkenseal around the threaded part of
> the cap, or it could be a broken pressure/vacuum relief mechanism inside
> the cap itself. You couldn't see the latter, and might not see the
> former if the seal is simply hardened and shrunken a little.
>
>> If the gas cap can be bad is it OK to get a gas cap from an auto store
>> or is it recommended one buys one from the dealer...the nearest one
>> being about 60 miles away.
>
>
> I sure wouldn't go to a dealer$hip for that kind of part, provided that
> my local auto parts store carries a direct replacement. Don't get some
> generic part, get one specific to your make and model of car. Unless its
> a limited-production exotic, which a Mitsubishi isn't, any auto parts
> store should be able to get the correct cap if they don't already have
> it on the shelf.
>
I'll get the part today. If that solves the problem I'll feel good. If
not, I'll get the car checked out.