Surging after changing O2 sensors

I have a '98 Corolla that needed new oxygen sensors so I replaced both with OEM Bosh units. Now the car is surging and often not moving much at all from a stop. I also changed the catalytic converter at the same time. I already reset the computer. Any ideas what is going on? It is not generating any codes.

Mike D.

Reply to
Mike Dobony
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"OEM Bosch" is an oxymoron. Get those out Bosch parts of there and get real OEM replacements.

BTW, did the catalytic converter really need to be replaced? If so, is the replacement OEM?

Reply to
High Tech Misfit

Um, that should say "get those Bosch parts out of there." :-/

Reply to
High Tech Misfit

Try cleaning the mass airflow sensor. Use an aerosol electrical contact / brake cleaner. You don't want to leave any residue on the hot wires. Don't touch it with your fingers or use a swab, just the spray should work in cleaning it. Good luck.

Reply to
user

Bosh units. Now the car is surging and often not

same time. I already reset the computer. Any ideas

It sounds like you are saying doing the work caused your engine to have a new problem. I would take a real close look to see if something like a vacuum hose is off or cracked. Maybe a electrical connector is off or something along those lines.

GL Dan

Reply to
Danny G.

Bosch is not an OEM supplier to Toyota so you do not have Toyota OEM Bosch O2 sensors installed. If you are looking for true OEM sensors, get Denso brand.

How do you know that your car needed new oxygen sensors and what kind of catalytic converter did you install?

Did you have to splice any wires to install the O2 sensors?

Have you checked for exhaust leaks? What is the manifold vacuum reading at idle?

As Ph@Boy suggests, you can try cleaning the air flow sensor, and while you are at it, use carburetor cleaner to clean the idle air control valve and check the black plastic intake snorkel between the air filter housing and throttle body.

Reply to
Ray O

I'm kinda surprised the cat would be gone that quick, unless it was fuel polluted, etc.. The OEM cats are very high quality compared to aftermarket. Many new aftermarket cats are junk in comparion. I've gotten to where I will change a cat as a last resort only, as usually it's still good nuff. I had emission test problems on my 89 accord, and eventually changed the cat. Believe it or not, the old cat was actually better at NOX reduction, than the new one. The new one had a very slight advantage at reducing hydrocarbons, but the old one was still plenty within range on that.. I kept bombing the NOX... I eventually squeaked it through by retarding the timing enough to pass.. Anyway, I'd beware of new cats.. They are cheap, and almost never as good as the OEM cats. And the OEM cats will last a long long time unless you abuse one with fuel, etc. I think most that change cats are more the victim of "guesswork" emissions techs, than actually needing one.. :/ In my case, I was close on NOX the first time, and had checked most everything related.. Soooo. I thought, well heck, a new cat should get me over the "edge" no problem, being mine was a 89.. Nope...It actually tested worse on NOX the 2nd go around, using the new cat. :( You live and learn... MK

Reply to
nm5k

I looked for a mass airflow sensor on this car and can not find any. If it has it it is part of the throttle body assembly, but I don't see one there either. It wouldn't be before the air cleaner, would it?

Reply to
Mike Dobony

I forget what the code was, but the common solution on the internet was to replace the oxygen sensors. The vehicle has over 200,000 miles on it.

No splices, as the had OEM connectors.

I don't have a vacuum guage any more. I'll have to go and get one.

I previously looked for the air flow sensor and found none on this vehicle.

Reply to
Mike Dobony

Next time, post here first. There are some knowledgeable people who can give you the correct answer instead of guesses. :-) For example, I would have explained how to check the O2 sensors first before replacing them.

It is possible that the Bosch sensors are causing the surging, although I doubt it.

The air flow sensor is mounted on the air filter housing. I'm not sure if your car has a mass air flow or manifold absolute pressure sensor, but it is the only thing with electrical wires attached that is hanging off of the air filter housing. Carefully unplug the connector to the sensor, remove any mounting screws. If the part that protrudes into the air flow is oval-shaped and has a thin wire inside, spray carburetor cleaner into the oval opening in the sensor, let the fluid drip out, let the sensor dry for a few minutes, and see if the wire is shiny. If the wire is black, keep cleaning but don't stick anything into the oval opening because if the wire breaks, you need a new sensor.

The idle air control valve is mounted on the throttle body.

One more thing to check... Remove the vacuum hose from the EGR valve and block the vacuum hose. If the problem goes away, the EGR valve may not be closing completely at idle due to black crud buildup inside. You can try removing the EGR valve and cleaning out some of the crud.

Reply to
Ray O

The code number was for the catalytic converter operationg outside of acceptable range, per AutoZone. It was there twice.

The surging is all the time, but the lack of power is at idle.

Reply to
Mike Dobony

Sounds like P0420. In the future, write down the specific code to save future diagnostic time.

By any chance, did you save the old O2 sensors? If you did, try replacing the front one and see if the surging goes away.

Also, check for exhaust leaks, particularly by the front O2 sensor.

surging can come from a vacuum leak, and the symptoms could come from an EGR problem. First, try replacing the old sensor and see if the surging goes away.

Reply to
Ray O

Yes, I believe that was the code.

Old sensor was tossed immediately. I would have to buy another to test it.

Reply to
Mike Dobony

OK, go to plan B: Unplug the O2 sensor(s) and see if the surging goes away. You will get a check engine light but you can clear it by pulling the EFI main fuse for about 10 seconds. In the future, you may want to keep old parts at least long enough to make sure everything is fixed.

Reply to
Ray O

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