Re: '89 Mustang check engine light
You are correct. The codes 21 and 24 went away when
warm. But the 31 remains. The car now is idling at a loping gate when cold,
but ok warm.
I mean ok/stumbling at about a 5 second rate each. Sounds like something
leaking air in, like the PCV or EGR.
I checked the PCV and it seems ok. A little leakage in the closed direction.
Probably time for
a new one of these. It has never been replaced. Also, It looks like I will
have to take the EGR out and clean it or replace it.
"Jim Warman" <firstname.lastname@example.org> wrote in message
> I'm going to assume that this test was performed when the motor was
> cold..... giving the IAT and ECT (codes 21 and 24) readings are out of
> self test range. To eliminate these as concerns, we would run the motor to
> operating temp and rerun the KOEO test....
> To address the memory code, we would need to perform the KOER test to see
> if we are dealing with a hard fault or an intermittent.... At any rate,
> the most likely cause for code 31 would be the EVP sensor on top of the
> EGR valve. Pay attention to "most likely"....
> These "ancient" electronic control systems offered relatively little in
> the way of self diagnostic capabilities. Occasionally, parts replacement
> can be considered a viable diagnostic step... especially if testing the
> sensor would cost more than replacing it.
> At the same time, it is important to pay attention to the base engine....
> particularly the fuel filter which seems to be often forgotten.
> While I am trapped to using the 1992 PC/ED (the oldest available on CD),
> the link supplied by the other respondant appears to contain some
> "Fred V." <email@example.com> wrote in message
>> Lately my check engine light has been coming on for short periods. It
>> on, then goes away, then comes on again. Otherwise the car runs fine.
>> What could it be?
>> KOEO test: on-demand codes: 21 and 24
>> continuous code: 31
>> 89 LX 5.0
>> 98K miles