For the cold start.... your PCM isn't even paying any attention to the O2
signal (simply because it is still too cold to generate a signal). If you
are recieving an O2 HEATER code, then the problem could well be an O2
sensor.... if you are getting a code like "O2 always lean", you more than
likely have some other problem making the O2 sensor experience a mixture
that is always lean. Changing the O2 sensor over and over and over wont fix
Let's take a look at your misfire - sometimes with a backfire and that makes
me want to say ignition... Somewhere, somehow a mixture is being lit at the
wrong time or unburned fuel is getting into the exhaust and lighting off.
One thing that an ignition misfire will deliver on an OBD1 car, is a lean
mixture (important to remember that the O2 sensor can only measure oxygen
content - as far as mixture goes, it dont know shit from shinola... all it
knows is high O2 content and low O2 content).
So... we have a misifre dumping a lot of (unspent) O2 down the pipe and a
Let's take a look at your MAF code... this car is over 10 years old and most
likely has it's original MAF sensor..... complete with it's lovely, warm
little fur coat. This collection of debris that gets past the air filter
element has an insulating effect on the sensing element in the MAF sensor...
the PCM thinks less air is getting into the motor than really is..... Less
air, did I say??? The PCM sees "less air" and reduces injector on time.....
leaning out the mixture....
So.... we have a misfire and an inaccurate MAF indication dumping a lot of
O2 down the pipe????
One last comment on the oil pressure.... if the pressure is "good" at idle
but approaching low at rpm, I would be concerned about oil pump
starvation... crap on the pick up screen as a likely cause.
Time to go back and have a chat with your mechanic....
"Steve Forester" <email@example.com> wrote in message
> "Tom Adkins" <firstname.lastname@example.org> wrote in message
> > Steve Forester wrote:
> >> Is it THAT stupid of an idea???
> > Yes. Used O2 sensors are in the same category as used brake pads, spark
> > plugs, windshield wipers, mufflers, ball joints, water pumps etc. Would
> > you buy these things used and put them on your car? You will replace the
> > O2 sensor(s) on your car, maybe, once in 10 years. At$100 for a pair
> > spread over 10 years, that's pretty cheap. O2 sensors actually rarely
> > fail. Do you think yours are bad?
> Yes, a local (and trusted) mechanic did a once-over on my 93 GT
> because of:
> (i) a miss -- usually accompanied by, but not always, a backfire -- at
> all RPMs or speeds, and
> (ii) the engine when "cold" -- December or July -- stalls out after about
> 5 seconds on the first start-up, I mean 5 seconds after each and
> every first cold-engine start-up, but on the second try, attempted
> immediately after the stall, the engine always starts "normally" and
> idles "normally" which it must do -- December and July -- for 5
> minutes before I attempt to drive it. If I tried to promptly drive
> after the second start, the car would sputter and backfire for miles.
> His once-over resulted in:
> o Good compression across all 8 cylinders,
> o Normal oil pressure at warm idle, but borderline-low oil
> pressure at 2,000 RPM,
> o MAF sensor code, and
> o O2 sensor code.
> Remove the spam-spoofing triple x's to email me directly.
> =+= Sarcastic remarks are always welcome!
> =+= They might as well be welcome since...
> =+= I am going to get them anyway.