2000 Toyota Corolla Myriad of Problems

So there are a thousand things wrong with my Corolla. My main concern is to get the check engine light to turn off so that I can pass inspection. I would like to pose all the different symptoms and hope that they all point to one problem, although I’m pretty sure there are at least two. A little bit of back story: bought it in 2005 with 50,000 miles on it, it has 93,000 miles on it now. I will present the problems in order of occurrence earliest to most recent:

1) Sucks up oil like no one’s business. Uses about 4 liters at least every 1500 miles. No smoke from the exhaust pipe, no leaking at all. It has been like this since I got it.

2) 2006: Check engine light came on. I cleaned the O2 sensor and it switched off. Not exactly sure about when it came back on, but probably not long after that

(6 months?) Haven’t worked on fixing it because it was required at the time to have it off for inspections

3) 2009 Two codes simultaneously as listed below with their meanings for Toyotas (checked at AutoZone):

Engine Code P0171

air/fuel mixture lean bank 1 (cylinder number denotes bank 1)

probable cause:

-low fuel pressure

-faulty maf/vaf sensor

-cylinder misfire condition

-faulty h2o/AF sensor

-large vacuum leak

and engine code P0420

catalyst system efficiency below threshold - bank 1

probable cause

-air leak in exhaust before h20/AF sensor

-fuel system fault

-faulty catalytic converter

4) 2010 Changed out spark plugs, they were white which from the car manual suggested that the engine may be running too hot (I’m assuming that this happens based on issue #1 when I don’t put oil in early enough)

5) After the spark plugs were change we checked the engine codes again, still two codes simultaneously but they are now:

P0171 and P0300. P0300 is defined as:

random cylinder misfire condition


-lean air/fuel ratio - fuel pump

-faulty maf/vaf sensor

-large vacuum leak

-ignition system fault

6) additional notes: I did try fuel injector in 2007 and i can’t remember if the check engine light turned off or not. I have checked from the top view all the different hoses that I could see and none of them have had obvious cracks - I haven’t checked from underneath.

It’s a real puzzler with possibly more than one source for the problem. I have researched a bit about all the problems but I just wanted to see if all of the clues could pin point one underlying problem with the car that would help me get that silly check engine light. I try to call the boys at the station, but I can never get through! I’m willing to try any DIY tips you may have! Thanks bunches. P.S. I need to get this fixed by the end of February to stay legal or I might have to move!

Everything except 1) could be the result of a faulty O2 sensor. You said you cleaned it. Try replacing it.

A faulty PCV valve may be responsible for the excess oil consumption, although a gallon of oil every 1500 miles is seriously excessive. If all that oil is going through the exhaust system it’s not doing the catalytic converter any good.

All of those “cause” lists are things that need to be checked. Do you ever have any of it checked, or do you just keep hoping that the car will miraculously heal itself? E.g. has the fuel pressure been checked? The MAF circuit? Has the MAF been cleaned? Check for vacuum leaks? Etc. You have this long list of problems and possible causes but say almost nothing about what has been done to try to address it.

Right, my bad, I said I had cleaned the O2 sensor but it was actually the MAF sensor that I cleaned so maybe it could be the 02 sensor causing the problems now. Weather is nice, I’ll try to take a look at it tomorrow.

“Sucks up oil like no one’s business. Uses about 4 liters at least every 1500 miles”.

Possible, Low compression. plugged catalytic converter, either could cause engine misfire.

A engine rebuild, and new catalytic converter may be needed to get the codes to go away.

IMHO The Last really good model year for a Corolla/Prizm was when the car had either the 4A-FE, or the 7A-FE engine. I think that was like 1997.

My mechanic told me that 2000 Toyota Corollas just burn oil after a certain point and that you have to keep replenishing it. He didn’t go into detail. He just said they tried to do something fancy. In any case, it does appear that this lovely feature is making me go through catalytic converters every 6 months. Right now my best plan is to just replace it each year with a cheaper aftermarket version before my birthday. I would love advice on a better plan that I can afford.

My guess is the oil control piston rings are worn, or caked with carbon build up which is causing the oil consumption. The only thing that can be done short of a ring job is to perform a piston soak. If a piston soak is what your mechanic did, and it didn’t help, then the only thing left is a ring job.