99 Camry - Bad mileage & Oil Consumption

[Chard]

I own a 1999 Toyota Camry LE with the 2.2-4cyl. I've owned the car since new and was accustomed to receiving outstanding fuel economy until the last year or two. The car currently has 85,000 miles and is well maintained with an oil change every 3,000 miles.

I am currently experiencing numerous problems with the vehicle. Currently it consumes about one quart of oil every 1,000-1,500 miles and returns fuel mileage of around 22 mpg. When the car was newer I was not as accustomed to checking the oil regularly. About four years ago I happened to check one day I took the car in for an oil change and they found the vehicle at least 2 to 3 quarts short of oil. Since that point I have always been dilligent to check at every fillup and add as necessary. Around the same time my timing belt failed at around 57,000 miles and was replaced along with the water pump.

I am baffled as to the loss of oil. The engine doesn't smoke and the plugs always seem clean when I check them. I've replaced the plugs, wires, air filter, and PCV valve regularly and yet my mileage has continued to worsen. It is not delivering any CEL's

About 3 years ago I took the car to the Toyota dealership to see if I had a sludging problem and was turned away saying that they could find no evidence under the valve cover.

Can anyone offer suggestions. This mileage is awful. What would you recommend?

[dc_98_cam]

Compression check on the cylinders might tell you something is wrong.
Possibilities..rings...valves seating properly...valve seals leaking oil into cylinders ... headgasket...
Another test that isn't too difficult is a coolant system pressure check....This would tell you if there are any leaks ...such as coolant entering a cylinder ... Does you coolant reservoir ever require topping up?

When you say you get 22 mpg, would you say that is mostly city driving? 22 mpg is just about right if mostly city.

[toyomoho]

The low fuel MPG and the oil loss may be too separate issues. Suggest you check the engine over closely for oil leaks, both engine off and on.

A leaking oil pump seal can easily cause this type of oil loss. Also check for leaks from the crank (both ends), camshaft, valve cover (also look in back of engine), distributor (if it has one) and oil cooler located underneath the oil filter (if equipped with one).

As for the MPG might be the No 1 A/F sensor, these can get lazy over the years. One symptom is lower MPG.

[fifa man]

for the loss of oil: It could be your valve cover gasket. Check the areas behind your valve cover. If there is oil around there its probably what it is. I had an oil leek and it just turned out to be the gasket

[Stillrunning]

The poor mileage and oil burning may be related if there are no leaks. If, as toyomoho says, the #1 A/F sensor is running a rich mixture then you may be getting some fuel in the oil which reduces its flash point and it will burn faster. You may also have a small exhaust leak that induces oxygen into the exhaust stream and that will send wrong signals to the A/F sensors which will run a rich mixture. You could get a $20 oil analysis which will show any excess fuel in the oil. An exhaust gas analyzer will show rich/lean.

[Kep]

When the PCV valve plugs up it allows pressure to build up in the engine and that could be forcing oil out somewhere. However, I would think that you would notice a pool of oil under the car or a lot of smoke if you were loosing 1 quart every 1500 miles. Don't know. It would be an easy check though.

If you do a compression check inspect the plugs for fouling. They may give you a clue.

There are a lot of places that oil can leak from. If your engine is dirty the first thing to do would be to clean it up so you can determine where any oil is leaking from.

You might go to an auto parts store for a free CEL code reading. Maybe there are some codes that don't cause the CEL to flash.

Kep

[Chard]

I guess I forgot to mention in my previous post that there is no evident oil leaks. The only exception to that was the last time I changed plugs there was a slight pooling of oil around the spark plug nearest the oil fill. I'm not sure, but I believe this might be due to spilling of oil when I add the quarts that are mysteriously disappearing. Otherwise, the engine is completely clean and I've never had any spotting on the garage floor.

Also, every 6 months to a year the idle will begin surging up and down while holding on the brake while in drive. I typically simply run injector cleaner through and that straightens that problem up for another 6 months to a year.

I'll probably have a compression test done to see how it holds up. I've considered the possiblitiy of a bad valve seat/guide or a problem with the rings.

For clarification of the A/F sensor. Are we referring to the Oxygen sensor or something else? If the Oxygen sensor, I believe this vehicle has two, correct? Should I replace both.

The oil problem is incredibly frustrating to me. The problem seemed to begin to occur just outside of warranty. I've never had a vehicle with so few miles consume oil, especially at this rate.

[91MR2quickNA]

For clarification:

1998+ California spec cars have Air-Fuel Ratio sensors (though I'm not sure if the downstream sensor is an O2 or A/F), and 2 cats
1997-2000 Federal cars have an O2 sensor and 1 cat
2001+ CA or Fed spec cars have Air-Fuel Ratio sensors and 2 cats (50 State Emissions Pkg)

A/F Ratio sensors are very expensive. Replace them only if you believe them to be a problem. Usually the OBDII system will catch a faulty A/F Ratio sensor because the A/F sensor has a wider range of operation than a traditional O2 sensor.

Ensure your PCV system is functioning correctly. Check the PCV valve for proper operation, and if you remove it, be sure to replace the gasket with a new one (so you might as well buy a new PCV valve anyway).

I think you should pop the valve cover (buy a new valve cover gasket beforehand) and check for sludge buildup. A malfunctioning PCV system can sludge oil very quickly, even with regular oil changes. The early timing belt failure is an indication that there is either signicantly more stress on the cams than normal, or the belt was just defective. I believe 1999+ 5SFEs have a 90,000 mile timing belt service interval.

The nuts on the spark plug tubes are 30mm (use a 6 point socket, not a 12 point ... a 12 point might strip the nuts).

Also, if the oil pooling is not oil spilled, replace the oil cap gasket as well.