Thread: I stumped. Idles and runs ruff. Codes P0300 P0135. New Cat Last year. Help

The Beast Background info: She is a 2002 Grand Prix GT with a mere 165,000 miles. In the past year I have replaced: Water Pump, Upper and Lower Intake Manifold Gaskets, Belt, MAP Sensor, Throttle Position Sensor, catalytic converter, Thermostat.

I was on home from work yesterday she was running perfect. I was low on gas but I decided to wait it out and made it home. This morning I was on my way to work to get gas and all of a sudden she started running horrible and the check engine light was flashing. I figured she was choking on fumes. I rolled into the gas station and put 16.3 gallons of regular gas in her. Fired her up and low and behold she was still running like ****. I went back to my apartment, I noticed a little bit of white smoke and a bad smell. I went auto zone they scanned for codes and found a p0300 random misfire, and p0135 oxygen sensor.

It is running about as bad as it did when the cat clogged up except when that cat clogged it gradually got worse, this time it just all of a sudden went to ****. It's like she idles ruff and keeps running ruff through all the RMPs. She feels weak when accelerating. The SES light flashes. I drove it to auto zone and was getting terrible gas mileage averaged 11 mpg on 7 mile round trip according to the digital read out.

Could a clogged fuel filter make it start running this ruff all of a sudden? I bought a new one but I can't seem to get the old one off.

My other thought was a vacuum leak but I can't find one.

The guy at auto zone thought the upper intake manifold may be leaking fluid into the cylinders. I took the throttle body off and didn't notice any damage. Was I looking in the right place?

Replace the 02 sensor no more PO135 still getting the p0300 though, and it is still running like a turd.

No signs of a blown head gasket. Oil and Water are clean.

Fuel filter or oxygen sensor.

how about the code for the o2 sensor?

change the o2 sensor and change your plugs and wires to help the misfire out.

The o2 heater circuit probably burned out or the wiring harness is messed up going to it.

Technical Description

Oxygen O2 Sensor Heater Circuit Malfunction (Bank 1, Sensor 1)
What does that mean?

This code refers to the front oxygen sensor on Bank 1. The heated circuit in the oxygen sensor decreases time needed to enter closed loop. As the O2 heater reaches operating temperature, the oxygen sensor responds by switching according to oxygen content of the exhaust surrounding it. The ECM tracks how long it takes for the oxygen sensor to begin switching. It the ECM determines (based on coolant temp) that too much time elapsed before the oxygen sensor began operating properly, it will set P0135.
Symptoms

You will likely notice poor fueleconomy the illumination of the MIL.
Causes

A code P0135 may mean that one or more of the following has happened:

• O2 Heater element resistance is high
• Internal short or open in the heater element
• O2 heater circuit wiring high resistance
• open or short to ground in the wiring harness

Possible Solutions

• Repair short or open or high resistance in wiring harness or harness connectors
• Replace oxygen sensor (cannot repair open or short that occurs internally to sensor)

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Technical Description

Random/Multiple Cylinder Misfire Detected
What does that mean?

Basically this means that the the car's computer has detected that not all of the engine's cylinders are firing properly.
A P0300 diagnostic code indicates a random or multiple misfire. If the last digit is a number other than zero, it corresponds to the cylinder number that is misfiring. A P0302 code, for example, would tell you cylinder number two is misfiring. Unfortunately, a P0300 doesn't tell you specifically which cylinder(s) is/are mis-firing, nor why.
Symptoms

Symptoms may include:

• the engine may be harder to start
• the engine may stumble / stumble, and/or hesitate
• other symptoms may also be present

Causes

A code P0300 may mean that one or more of the following has happened:

• Faulty spark plugs or wires
• Faulty coil (pack)
• Faulty oxygen sensor(s)
• Faulty fuel injector(s)
• Burned exhaust valve
• Faulty catalytic converter(s)
• Stuck/blocked EGR valve / passages
• Faulty camshaft position sensor
• Defective computer

Possible Solutions

If there are no symptoms, the simplest thing to do is to reset the code and see if it comes back.
If there are symptoms such as the engine is stumbling or hesitating, check all wiring and connectors that lead to the cylinders (i.e. spark plugs). Depending on how long the ignition components have been in the car, it may be a good idea to replace them as part of your regular maintenance schedule. I would suggest spark plugs, spark plug wires, distributor cap, and rotor (if applicable). Otherwise, check the coils (a.k.a. coil packs). In some cases, the catalytic converter has gone bad. If you smell rotten eggs in the exhaust, your cat converter needs to be replaced. I've also heard in other cases the problems were faulty fuel injectors.
Random misfires that jump around from one cylinder to another (read: P030x codes) also will set a P0300 code. The underlying cause is often a lean fuel condition, which may be due to a vacuum leak in the intake manifold or unmetered air getting past the airflow sensor, or an EGR valve that is stuck open.

you have a fuel filter in line on the car.

but thats not your problem at all.

its the o2 sensor your beating around changing with fuel filter questions.

rule one fix known problem, the codes not lying. and you have all the symptoms for it.

check your wires to the o2 plug are free of damage and if found to be good replace the sensor.

The o2 code isnt for it running lean. It's because it's not heating up.

Originally Posted by wavedout33

u need a special tool to get that 1 side of the filter off...u may be able to borrow one to get it off....have fun it's goin to pour gas out....and follow scottys advice....the advice i gave u is a last ditch effort after everything else has been replaced....

Are you talking about the fuel filter? No special tools are need

Originally Posted by wavedout33

u need a special tool to get that 1 side of the filter off...u may be able to borrow one to get it off....have fun it's goin to pour gas out....and follow scottys advice....the advice i gave u is a last ditch effort after everything else has been replaced....

Changed mine in a parking lot with a screwdriver and pliers in the car.