High CO/HC on hard accelerating

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Old 04 Aug 2003, 08:21 pm   #1 (permalink)
Roy Lipscomb
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Default High CO/HC on hard accelerating


Our 1990 4-cyl Camry in great shape.

On a 700-mile trip two weeks ago, we got about 41 mpg.

(Five years ago, when I had ignorantly overinflated
the tires to 45psi, we got about 45 mgp.

(Yes, our odometer does check out against the highway
mileage markers.)

Though the car's got 161,000 miles, it uses only a
quart of oil per 3000 miles. And probably most of
that is leaking from around the distributor O-ring.

So what's the problem? Well, the State of Illinois
deems our car _carriagia not grata_.

Two years ago, our car passed the State emissions
test on the first try. But it failed this year's
test twice. It's related to excessive emissions
that occur during heavy acceleration.

A copy of this year's first test is at--


Following that first test, I did the following.

* Installed new--
* O2 sensor.
* Distributor cap and rotor.
* Spark-plug wires.
* Spark plugs.
* Air filter.
* Gas cap.

* Replaced--
* Throttle position sensor.
(One of the "opened/closed" sensors was dead.)

* Verified specs on--
* Replacement throttle-position sensor.
* Igniter.
* Air temp sensor.
* Water temperature sensor.
* Air flow sensor.
* Ignition coil.
* Ignition timing.
* OBD (no malfunction codes).

The reward for all that labor? The car failed the second
emissions test as well.

A copy of this year's second test is at--


Some observations:

1. There is a very faint hiccup when we accelerate from a stop.

2. If I race the engine at idle while checking the O2 sensor,
the voltage swings to the high (rich) end and stays there.
(I've only tried this three or four seconds at a time.)

3. Two or three times in the past three years (until I learned
better), I overfilled the gas tank.

4. We had the fuel pump replaced last summer, five months
before the first of the above two tests.

Every month or two since then, we notice a smell of raw
gasoline, usually when we have just exited the car. The
smell's hard to trace, but may be coming from the gas tank area.

5. I've noticed that a fuel-line bend near the fuel tank is
pinched to about half its normal diameter. I don't know if
it is a feed or a return.

I asked our our mechanic about correcting it, but he says,
"Leave well enough alone."

Rather than diagnose the emissions problem, our mechanic says we
should just put on a new catalytic converter. (We bought the car
used; it may still have the original cat.)

I've read that a new cat can help mask an engine problem. But I'd
rather cure the problem than simply mask it or throw parts at it.

Can anyone pinpoint what's causing the problem?

Best Regards,

Roy L.
Mary G.

P.S. Remove the "x" from my email address.
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