'89 Corolla trouble code #25? (carbureted California car)

Hi all,

1989 Toyota Corolla SR5, Carbureted 4AF, California emissions, 146k miles, runs great, thanks largely to all the help I've gotten from this newsgroup since buying the car in 1999.

Check Engine Light turned on while I was driving (stop and go local driving)-- I pulled the trouble code and it's #25. Runs fine. Engine temp was normal operating temp. Came home. 15 minutes later, for good luck, I sprayed some carb cleaner in the carb. Drove the car around a few miles, the check engine light did not come back on.

Could someone tell me what this code is and what I might want to do next? From what I could find from old posts, it may mean "running lean" and that the next step is to change the O2 sensor? (or can it be cleaned?)

If so, does anyone know if a California car would use the same O2 sensor as a non-California car?

The only other history of relevance, if any:

  1. gas mileage is normal; passed Emissions fine 5 months/2000 miles ago
  2. had entire new exhaust system installed last month, including new catalytic converter.
  3. 5 years/40,000 miles ago, the car was misfiring when cold and had trouble codes #31 and #41. I first changed the Thermo vacuum switching valve, which did not help. Then changed the Throttle position switch, which solved the problem.
  4. car's now only driven about 4k miles a year, mostly local driving
  5. it is getting colder quickly here in Boston

Hope it's unlikely that the car needs a new carb, b/c I just put $1100 into it this past year and will go crazy if I need to spend any more on it.

Thanks for any and all advice! John snipped-for-privacy@yahoo.com

Reply to
johnyang97
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25 Air/Fuel ratio lean.

Reply to
Hachiroku

I did not check to see if trouble code 25 means that the engine is running lean, but assuming it is, spraying carb cleaner enriches the mixture.

Check to make sure the air filter is not dirty. Remove the air filter element and shine a light behind it. You should be able to clearly see the light through the element. If the light is dim or not visible, replace the air filter element.

The system knows it is lean from the O2 sensor's output, so I would start by checking O2 sensor function. Disconnect the O2 sensor and hook a volt meter up to the sensor terminals. With the engine running steady at about 2,500 RPM, voltage should fluctuate at least once per second. If it does not, then the sensor needs replacement. I do not know if CA vehicles have a different O2 sensor or not, but I suspect not.

If the O2 sensor is functioning properly, then the carb needs adjustment. I would leave this to a competent technician.

Reply to
Ray O

HI Ray, As always, thanks for your help--

Replaced it with an OEM Toyota air filter last week, since the old one was dirty, so it's unfortunately not just the air filter.

Thanks for the tips on checking the O2 sensor. I hate to admit it, but I am not sure where to find the sensor--my Haynes manual is at my parents' house 250 miles away. I'll see if there's anything online to point me in the right direction. My guess is it's ok to drive the car lean for a while? (am tempted to make that 250 mile drive soon)

...hmmm, I wonder if any good carb mechanics still are around. I live in Boston where cars rust out quickly, and many mechanics probably have not touched a carb for years I'd think. Carb work sounds like major $$$$ too :(

Thanks again, John

Reply to
johnyang97

HI Ray, As always, thanks for your help--

Replaced it with an OEM Toyota air filter last week, since the old one was dirty, so it's unfortunately not just the air filter.

Thanks for the tips on checking the O2 sensor. I hate to admit it, but I am not sure where to find the sensor--my Haynes manual is at my parents' house 250 miles away. I'll see if there's anything online to point me in the right direction. My guess is it's ok to drive the car lean for a while? (am tempted to make that 250 mile drive soon)

Could the car's recent catalytic converter replacement (500 miles ago the entire exhaust sytem was replaced) possibly have anything to do with the problem? I'm loathe to take the car back to the shop because they had trouble replacing the exhaust system, and I'm not confident they would tackle this problem right-- also, I'd rather fix it myself if possible to save money. The cat. converter was $140 so obviously not OEM.

...hmmm, I wonder if any good carb mechanics still are around. I live in Boston where cars rust out quickly, and many mechanics probably have not touched a carb for years I'd think. Carb work sounds like major $$$$ too :(

Thanks again, John

Reply to
johnyang97

The O2 sensor will be in the exhaust system somewhere between the engine and the catylitic converter. It will be the only thing with wires sticking out of the exhaust.

Where in the Boston area are you?

Reply to
Ray O

Hi Ray,

Thanks, I'll try poking around. I wonder if I'll have better luck looking from under the hood or under the car? I'm hoping #1 but am guessing it's #2.

Right now I work in downtown Boston at Tufts-New England Medical Center and rent an apartment in Brookline, which is a town about 2-3 miles west of downtown Boston, on the B/C/D Green Line T, if you are familiar with the public transportation system here.

Thanks again, John

Reply to
johnyang97

Start by looking under the hood. My guess is that it will be in the exhaust pipe just under the exhaust manifold. If not, then you have to get down and dirty.

Toyota of Boston on Brighton Ave, Expressway Toyota in Dorchester, Toyota of Watertown on Arsenal St Clair Toyota in West Roxbury are the closest Toyota dealers.

Although I lived and worked in New England for about 10 years and called on these dealers, that was close to 15 years ago. They all had good service departments when I called on them and I imagine that they continue to provide good service.

Reply to
Ray O

Right outside Chinatown, near the Wang Center? (and a holler from the Combat Zone, too?...ugh.)

I haven't been there for a few years...have they cleaned that area up? I have to admit...I used to leave my Brand-New Corolla GTS on Beech st. in Chinatown, and nobody ever bothered it!

I'm in Western Mass...thank God! Nah, I liked Andover. I was there for a year and then moved to Nashua. Used to work in Andover. Boston was a Saturday afternoon trip.

Reply to
Hachiroku

Disconnecting it won't work. That fluctuation you see is the the control mechanism working WITH the o2 sensor. There will be a test port where you can connect your voltmeter without disconnecting the o2 sensor.

On my '85 it's near the firewall on the passenger side. When you remove the rubber cover it is labeled ... can't remember exactly what it says, but it's clear that it's for the o2 sensor.

If the fluctuations don't occur, it's either the o2 sensor or the control mechanism. On the 85, the carb is set too rich and a couple of air bleeds are activated to lean the mixture. Lack of control could mean the air bleeds or the valves are plugged or leaking. One trick is to force a rich condition by introducing propane into the intake. That will cause the o2 sensor to stay in the rich state (don't know if it's the high or low voltage at the test connector). That gives you some idea how much of the control loop is active. Lean is created by pulling hoses to create an air leak. But based on your code, going lean isn't an issue for you.

Reply to
Kurt Krueger

Good point! You disconnect to measure resistance, not voltage fluctuation.

Reply to
Ray O

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