Mechanics

OLDS ACHIEVA REPEATED 02 SENSOR FAILURES

1997 Oldsmobile Other

I have a 1997 olds achieva 4 cylinder with 85K miles, My mech runs the OBD and says the 02 sensors are bad. It is now on it's third set of sensors in less than a year. Currently the car is blowing heavy black smioke, fuel mileage is terrible and it misfires under load. I pulled the 4 wire 02 sensor out of the catalytic convertor and the heavy black smoke went away. It still misfires under load but not as bad. I was thinking about also pulling the 02 sensor before the cat converter to see what happens. I have done a complete tuneup on the vehicle to no avail. Any ideas? Will it harm the engine to leave the 02 sensors outside the system but still hooked up?
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Jmc
December 29, 2006.



Is that a Quad 4? If so then you need the coil housing most likely. It acts as the wires. Also check the fuel pressure regulator for a ruptured diaphram. That will dump raw fuel into the intake. There are many things that it could be, try those and get back to me

Tiny
Jack42
Dec 29, 2006.
It is a 2.4L twin cam, how do I check the fuel pressure regulator? Where is it? I replaced the fuel pump a while back, it was bad. Where is the coil housing located? Thanks

Tiny
Jmc
Dec 29, 2006.
Let's start from the root(s).
Black smoke is an indication of excessive fuel consumption. A leaking fuel injector, dirty air cleaner element, like jack have said earlier, a defective fuel pressure regulator, or defective fuel control sensor could cause this. You car is equipped with a catalytic converter; the rich mixture may cause a strong rotten egg smell

Your first question was to remove the O2 sensor to solve the problem.
The PCM monitors the activity of the converter by comparing the signals of HO2s located at the front of the converter with the signals from HO2s located at the rear. If the sensor outputs are the same, the converter is not working properly and the malfunction indicator lamp (MIL) on the dash will light.
Some mechanics can just replace the second HO2s because the computer pointed finger at it.
For me, the second oxygen sensor is telling your computer the truth about what is going on in your combustion chamber that may have cause the converter not to work as it should. Check your converter.
Converter is normally trouble free emission control device, but two thing things can damage it: One is leaded gasoline, I'm sure you do not use that so I do not need to go in details.
The second is overheating. If raw fuel enters the exhaust because of a fouled spark plug or other problem, the temperature of the converter quickly increases. The heat can melt the ceramic honeycomb or pellets inside, causing damage to the to the exhaust valves due to the excess heat.

Let's come back to fuel regulator.
A fuel pressure regulator controls the amount of pressure in the system. Mechanical fuel pumps often contain built-in pressure regulators. However in vehicles with electrical fuel pumps, the fuel regulator is installed in the fuel system between the fuel pump and the fuel distributor.
If you do not find it, let an ASE technician take care of this problem.

Tiny
Mathiaso
Dec 29, 2006.
I changed both the forward 02 sensor and the 02 sensor at the catalytic converter, And the problem remained. Vehicle never had leaded gasoline in it. However I did replace the fuel pump in the tank a while back. There is no rotten egg smell from the converter. How do you check a converter?

Tiny
Jmc
Dec 29, 2006.
On the top of the engine there is a plate with 4 bolts holding it down. Remove them and pull the plate off. There are 4 boots that go over the plugs and on to the coil housing. the coil housing is the large white thing with the coils attached to it. replace the boots at the same tiome as the coil housing.

Picture:
http://images.wrenchead.com/smartpages/partinfo_resize/DUS/10475706.jpg

The best way to determine if a catalytic converter is working is to check the quality of the exhaust. This done with a four-gas exhaust analyzer. The result of this test should show low emission levels if the converter is working properly
Another way to test a converter is to use a hand-held digital pyrometer. An electronic device that measure heat.
But do not quick condemn the converter because it needs a steady supply of oxygen from the air pump. A bad pump, faulty diverter valve or control valve, leaky air connection, or faulty computer control over the air injection system could be preventing the needed oxygen from reaching the converter.

Tiny
Mathiaso
Dec 29, 2006.
I checked the fuel pressure regulator there is no fuel in the vacum line. I replaced the coil housing. And put the 02 sensor back in the catalytic convertor. It has not helped the problem. I am wondering if the fuel pressure regulator could be bad without letting fuel into the vacum line? I am not sure where to go from here, replace the fuel regulator on a whim? Just in case. Whenever driving under load the engine seems to hesitate and bog down then adjust and ramp up to speed, as I play with the accelerator it can take off or bog down depending on how much gas I am giving it.

Tiny
Jmc
Dec 30, 2006.