99 Miata EGR light - only when tank is 1/2 full

Perhaps I missed the answer to this question someplace in this thread:
Did someone check for codes when the light was on? You can do this with
an relatively inexpensive code reader or rent one for free from your
local Autozone store. That would be a good first pass at determining
what is wrong.

Ken


wrote:
> The EGR is not monitored as an individual item.
>
> Its performance is inferred by other engine parameters. The test is
> along the lines of engine at operating temp, rpm at a constant 2000 or
> above so that there is enough back pressure to let the exhaust flow
> into the intake manifold, the ECM opens egr solenoid to put vacuum on
> the egr and monitor O2 sensor output and fuel flow or rpm. If the
> test parameters are not in range, CEL light turns on and code is
> stored. The light will go off the moment the operating condition of
> the engine changes.
>
> You did not mention if your mechanic tested the EGR solenoid and for
> Viacom leaks. They also can trigger the code.
>
>
>
>
>
> On 10 Feb 2007 07:31:40 -0800, wrote:
>
>> On Feb 6, 11:13 pm, "Chas Hurst" > wrote:
>>> "XS11E" > wrote in message
>>>
>>> .. .
>>>
>>>> "Chas Hurst" > wrote:
>>>>> There is no EGR light on my '99. Are you refering to the CEL?
>>>>> When you replace the cap on the fuel filler after fueling, do you
>>>>> twist it tight for at least one click? If not you can get the CEL.
>>>> Shouldn't that show up before a half a tank is used?
>>> Dunno, I tighten the cap properly. And I'm not gonna tempt the CEL gods by
>>> leaving it loose.
>>
>> Yes....I do tighten it.....now it's become intermittent. It comes on
>> for a few days and then goes off for a few days
>> (Check Engine showing EGR failure). Seems to be no rhyme or reason.
>> If it was the EGR valve wouldn't it come on and stay on? My repair
>> person wants to change the EGR valve - $300 but I hate to do that if
>> it's not a fix. Also he checked the exhaust ports and they're clean.
>> I'm at the point of just putting electric tape over the light so I
>> can't see it....but my remorse is that I don't want to be responsible
>> for polluting the air if that's what is happening.
>> Any other thoughts of why it comes and goes?

On Feb 10, 4:09 pm, KWS > wrote:
> Perhaps I missed the answer to this question someplace in this thread:
> Did someone check for codes when the light was on? You can do this with
> an relatively inexpensive code reader or rent one for free from your
> local Autozone store. That would be a good first pass at determining
> what is wrong.
>
> Ken
>
>
>
> wrote:
> > The EGR is not monitored as an individual item.
>
> > Its performance is inferred by other engine parameters. The test is
> > along the lines of engine at operating temp, rpm at a constant 2000 or
> > above so that there is enough back pressure to let the exhaust flow
> > into the intake manifold, the ECM opens egr solenoid to put vacuum on
> > the egr and monitor O2 sensor output and fuel flow or rpm. If the
> > test parameters are not in range, CEL light turns on and code is
> > stored. The light will go off the moment the operating condition of
> > the engine changes.
>
> > You did not mention if your mechanic tested the EGR solenoid and for
> > Viacom leaks. They also can trigger the code.
>
> > On 10 Feb 2007 07:31:40 -0800, wrote:
>
> >> On Feb 6, 11:13 pm, "Chas Hurst" > wrote:
> >>> "XS11E" > wrote in message
>
> 4...
>
> >>>> "Chas Hurst" > wrote:
> >>>>> There is no EGR light on my '99. Are you refering to the CEL?
> >>>>> When you replace the cap on the fuel filler after fueling, do you
> >>>>> twist it tight for at least one click? If not you can get the CEL.
> >>>> Shouldn't that show up before a half a tank is used?
> >>> Dunno, I tighten the cap properly. And I'm not gonna tempt the CEL gods by
> >>> leaving it loose.
>
> >> Yes....I do tighten it.....now it's become intermittent. It comes on
> >> for a few days and then goes off for a few days
> >> (Check Engine showing EGR failure). Seems to be no rhyme or reason.
> >> If it was the EGR valve wouldn't it come on and stay on? My repair
> >> person wants to change the EGR valve - $300 but I hate to do that if
> >> it's not a fix. Also he checked the exhaust ports and they're clean.
> >> I'm at the point of just putting electric tape over the light so I
> >> can't see it....but my remorse is that I don't want to be responsible
> >> for polluting the air if that's what is happening.
> >> Any other thoughts of why it comes and goes?- Hide quoted text -
>
> - Show quoted text -

Good feedback....thank you very much. Will check it all...quite
desparate at this point.