2001 Toyota Corolla Needs Help

Here?s a description of my car:

? 2001 Toyota Corolla S

? 130K miles

? Automatic

The engine light has been on for 1 ? years. It does not pass inspection. It sputters when it runs. When the accelerator is pressed to the floor it loses power (almost as if the accelerator is not pressed) and the RPMs surge between 1800 and 2000.

There are rare occasions, for about 5 seconds, it runs without any hesitation, but immediately falls back to the sputtering. The engine light has been reset several times but it always comes back on.

Getting up to speed takes forever. When it does get up to 50 or 60 MPH (it does it only on the level) if the accelerator gets pressed to the floor, the car will slow down to 15 MPH and the RPMs will drop to surge between 1800 to 2000. If the accelerator is slowly let up, there is a point where the car will slowly speed up again and the RPMs will rise.

Here?s a list of things that have been replaced:

? Oxygen sensor near manifold

? Spark plugs

? Fuel injectors cleaned out (professionally)

The last code the car was given was PO300 (multiple cylinder misfire.) Any suggestions on what the problem could be?

Sounds like a fuel problem. You should try testing the fuel pressure. Or start by changing the filter, it’s due anyway. Sometimes a clogged fuel filter can reduce the fuel pressure considerably and eventually cause fuel pump failure.

Also, check the coils and spark plug wires if you have them. Multiple cylinder misfires are generally due to bad ignition components. And with 8 years and 130K miles, anything can be suspect.

BTW, what brand of spark plugs did you use? Some engines are more sensitive to plug brands than others. Toyotas love NGKs.

This sounds to me quite like a fuel metering problem. The metering of the fuel is performed by the ECU based on a number of different sensor inputs. They measure the manifold’s absolute pressure, the air entering the engine at the air intake, the position of the throttle, the speed of the crankshaft, the temperature of the engine, the oxygen level of the exhaust stream, and perhaps one or two items I’m overlooking.

Because of the way it’s reacting to pressing the throttle I’d suspect the throttle position sensor, the mass airfolw sensor, or the manifold absolute pressure sensor as prime candidates. Each of these can be individually checked. Why you’re not getting more specific codes is beyond me.

As rripstop mentioned, low fuel pressure is another possibility. That too would cause your symptoms. That can be checked with a simple prsesure test and the cause could be the pump or the fuel pressure regulator. The surging would suggest the regulator.

If the parts you mentioned were changed by a shop, you need a new shop.
If you’ve been changing parts yourself hoping to fix it, you may want to consider bringing it to a shop. You’ll likely save a lot of money in the long run.