High Co/hc On Heavy Acceleration From Cruising

[lugnut]

Hi,

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--

http://www.ripco.com/~lipscomb/images/nov18.gif

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--

http://www.ripco.com/~lipscomb/images/july2.gif

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 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.

[Sandman]

Low cylinder pressure causes high HC. A compression test would determine that. Also the culprit may be your fuel pressure regulator.

[lugnut]

Sandman,

Thanks for your reply.

My sense is that cylinder pressure is OK, because the

car runs smooth and we are getting such good milage

on the highway (41 mpg). But I suppose I could buy

a pressure guage to check it out.

As to the fuel pressure: If that was excessive, wouldn't

we have emission problems at lower speeds as well?

Regards,

Roy

A

[Sandman]

I noticed that you did'nt include a new pcv valve on your list of new parts. cheap & easy.

You stated that you use 1 qt. of oil every 3000 miles. That tells me that either your valve guides/seats are leaking and you are getting oil in the combustion chamber or you are getting blowby into the crankcase. this is when the piston rings let some of the flame front past and it scorches a small amount of oil. and as stated, a wet/dry compression test could verify/eliminate this as a suspect. wet/dry= tested normally then a couple squirts of oil in plug hole and test again. compare results. If the dry is lower then the wet then you are getting blowby. If they are both similar then it's valve seats. a faulty pcv valve can also allow oil to be sucked into the intake manifold.(DON"T FORGET TO UNPLUG YOUR IGNITION COIL BEFORE CONDUCTING THIS TEST!!!)

Onto the fuel pressure. It will and should run fine at idle and normal driving even if its bad sometimes. You would have to tee a pressure guage into the fuel line and put a vacuum pump on the pressure regulator hose fitting.

Turn the key to on but don't start it. this will power your fuel pump. check your pressure. now apply vacuum to the regulator. check the guage and the pressure should go up. also, check the vacuum pump line for fuel as there should be none. if the pressure did not go up then the regulator is bad. and if there is fuel in the vacuum line the regulator is bad.

compression ties into this because with low compression you will have a less than optimal ignition of the air/fuel mixture which could let too much unburnt fuel into the exhaust.

And a bad fuel pressure regulator would cause lean air/fuel mixture

high hydrocarbons can be cause by an excessively lean or an excessively rich air fuel mixture.

If you have any other questions, feel free