"I looked at the voltage with a scanner and found both downstream and upstream o2 sensors zig zag up and down at idle. I appreciate any input"
P0420 will set when this happens.

 

The P0420 code has nothing to do with the jerking acceleration issue in my opinion. Many cars, including mine, had or have that code and still run smoothly. Could possibly be a throttle body issue. Possibly a fuel supply issue. Definitely needs diagnosing. No other codes I presume?

 

There aren't any other codes. I'll see if the throttle body needs cleaning then i'll go from there

 

Iva had that happen when primary 02 sensor went out. Has it been replaced?

 

No, hasn't been replaced. I'll look into it

 

You can start with something easy. Check the spark plugs. I've had somewhat similar issues on a Hyundai. The plugs were the culprit.

Do you have power on the freeway when going uphill or trying to pass other vehicles? If you have poor power and the transmission behaves strangely, your catalytic converter could be plugged up. Had a Mazda which did that and sure enough, the cat was 90% plugged up, which could cause P0420 and the symptoms you described. You can check using an infrared/laser thermometer. With the car fully warmed up, increase the idle to something like 2500 RPMs. Check the temp of the exhaust pipe right before it goes into the cat. Check the temp right after the cat. The after cat temp should be much higher than the before cat temp. If it's not, you'll need to remove the cat and take a looksie inside the mesh media to see what it looks like.

 

Spark plugs likely have oxidation buildup on the threads and are not properly grounded, causing it to misfire under load... Throw in a set of DENSO 5303 Iridium Power spark plugs for only $4.86 each.

2005 TOYOTA COROLLA 1.8L L4 Spark Plug | RockAuto

IRIDIUM POWER - Features | Products | SPARK PLUG | Automotive Service Parts and Accessories | DENSO Global Website

 

As this is likely the case after 16.5 years, you'll have to be very careful removing your old spark plugs. It'll be easier if the engine is still warm... Just barely break them loose first, blow out the spark plug holes if you have an air compressor, spray in a bit of WD-40 with the red plastic tube. Make sure your ratchet extension is held aligned in center of spark plug hole. Start gradually loosening a bit then tighten a bit back and forth, slowly and carefully working them out. Blow out the holes again before fully unscrewed, then remove and replace with new spark plugs.

 

Sorry about the long absence I've been very busy lately. Thanks for the suggestions and I've read all of them and tried them out. Anyways, I cleaned the MAF and Throttle Body, and I checked out all spark plugs, and they were fine, I replaced all of them just a few months ago, and I've changed out the primary O2 sensor with a new Denso one, and it made an improvement with acceleration, jerking is gone for the most part but very rarely does the jerking come back. I reset the code and it reappeared a day later. I used the laser thermometer like John Anthony suggested, and the cat going after the downstream O2 sensor failed the test as the temperature after that cat was about 100 degrees F lower than before the cat. I haven't yet tested the cat before the sensor as I can't really maneuver myself to measure the temperatures. Would the bad cat before the sensor suggest the front one is also bad thus triggering the code?

 

Sorry about the long absence I've been very busy lately. Thanks for the suggestions and I've read all of them and tried them out. Anyways, I cleaned the MAF and Throttle Body with no effect, and I checked out all spark plugs, and they were fine, I replaced all of them just a few months ago, and I've changed out the primary O2 sensor with a new Denso one, and it made an improvement with acceleration, jerking is gone for the most part but very rarely does the jerking come back. I reset the code and it reappeared a day later. I used the laser thermometer like John Anthony suggested, and the cat going after the downstream O2 sensor failed the test as the temperature after that cat was about 100 degrees F lower than before the cat. I haven't yet tested the cat before the sensor as I can't really maneuver myself to measure the temperatures. Would the bad cat before the sensor suggest the front one is also bad thus triggering the code?

Pull down the mid pipe and check the cat for plugging.

Does your scanner show any pending codes?

If the 2 sensors are in a loop, then the lower o2 isn't agreeing with the primary o2. Typically you want to change the o2 sensors in pairs.

You can test the o2 sensor but applying heat and watch how quick it falls during cool down. If it's slow, then it's no good.

 

The cat can be bad itself or possibly have rust holes in it causing air leakage. Mine was like that and had to be replaced and the P0420 went away.

 

Alright guys I could of caused a second problem by my own hand. My last post said that I cleaned the MAF and Throttle body, but that was my intention and didn't actually do it. Sorry about that it was late and I just wanted to go to sleep. Anyways, I disconnected negative terminal on the battery, cleaned both TB and MAF for REAL now. I removed the throttle body to clean it and let it sit overnight to make sure any cleaner had evaporated away, same thing with the MAF. I made sure to put everything in correctly. I started up my car and it would not start. I messed with the throttle a bit and no dice. I then decided to disconnect the MAF, then the car started after a few tries, idling at about 2000 RPM. I shut off the car, then plugged in the MAF again, then the car started back up, jumping between 2000 and 3000 RPM until it eventually settled down. I drove it and found that acceleration had degraded again to the point before I replaced the primary O2 sensor. I decided to replace my MAF for a Duralast, and acceleration improved again, BUT I noticed when I started the car when it was warm, the RPMs would shift slowly between 1000RPM to ~700RPM until it settled. To add to my misery, the jerking when accelerating from a stop worsened, to the point that when I pressed on the gas, the car would just briefly shake, then get going with the jerking. Getting on the interstate is no problem though, jerking in this situation is rare. At last, sometimes when the car is at idle, the rpms would slowly jump between 700 and 600RPM then the car starts to shake when it drops to 600RPM, and short term fuel trim would go between -3 and +3. MAF reading is static. This would happen for about ten seconds until it settles back to 700RPM, then it would occur again a few moments later. How ** am I?

 

Since you disconnected the battery, the ecu will go through a relearn of all the inputs. For the MAF, put back the original Denso MAF. Our engines are very picky when it comes to certain parts.

Go over the areas that you worked in and make sure nothing is loose or disconnected.

 

Should I disconnect the battery before replacing the original MAF?

Also to add more details, idle cycles between 1000 and 800RPM when A/C is on, occasionally drops to 600RPM, effectively turning my corolla into a maraca.

 

You should check your intake manifold gasket. Then, check your fuel injectors. They are likely dirty and the injector o rings may be hard and brittle by now and needs new ones. There are lots of videos to DIY to clean injectors.

I would disconnect the terminal for around 1 hour and let the car sit. During that time, reinstall the maf sensor and double check everything you took off along with the intake manifold. The original black one will cause unstable idle. Behind the intake manifold is a hidden vacuum connection. Most that have done this, have missed it.

DIY MAF

DIY 2003-2008 Corolla, Matrix, Pontiac Vibe MAF Sensor...

This is something quick I made up. It is really easy to do. This applies directly to 2003-2008 Corolla, Matrix, and Pontiac Vibe and similarly to all Toyotas that use the 2 bolt MAF Sensor from basically the 1990's to Present. Disclaimer: Myself or Toyotanation are not liable for any damage or...

www.toyotanation.com

DIY Intake manifold gasket

DIY 2003-2008 Corolla, Matrix, Pontiac Vibe Intake...

Well I am up here in Virginia for a little while and it's been pretty cold. The past few days my idle has been very low and I knew my original intake gasket had run its course (104k is alright with me). So I headed over to Priority Toyota and spent around 7 bucks and change to get an updated...

www.toyotanation.com

Since you have a 2005, your throttle is DBW(drive by wire). Here's a DIY for TB

DIY 2005-2008 Corolla, Matrix, Pontiac Vibe DBW Throttle...

Ok the much needed DIY for DBW Throttle body cleaning. I have used this method for hundreds of Toyotas and my own several times. Never had an issue. This is similiar for all Toyotas that use DBW with the differences being the removal of the air hose, etc. This is by far the easiest throttle to...

www.toyotanation.com

 

Alright I unplugged the battery for around an hour and a half and went over every possible hose and connector and found that everything looked fine, no loose hoses or cracks, etc. I replaced the original Denso MAF and started the car. Car idled at a about 1700RPM before it settled down to around 700RPM about 2 minutes later. The car made a quick hissing sound and is now idling at 1000RPM. I will go out for a test drive.

 

Alright guys very bad news. I took out the car for a test drive, everything going well. Suddenly when I gave it gas it didn't respond. I coasted down a major road until I found a side street and jerking it there. The car is acting erratic now. I turn off then turn it back on, then the car made a hard knocking sensation when I put in drive. Accelerating was almost nonexistent , but flooting the gas gas gave me the slightest power to get to a church where I am stuck typing this now. Idle is very erratic and the car is violently shaking and there's no way I can make it home now. Send help. (Not really).

 

When you arrive home, it's time to check for vacuum leaks. If you have a hand actuated vacuum pump, put in 5 in.hg and spray soapy water. Including the intake manifold.

 

Ok guys, PSA from a certified dummy.

I limped it back home and scanned the car, which gave back P2111, Throttle Actuator Control System Stuck Open. I popped the hood and loosened and pulled the air hose back to find a piece of cotton wedged between the valve and housing which prevented it from opening, resulting in little to no power and erratic idle. The rag I used was brand new.

 

Did the code go away? Throttle response better?

 

Is the intake hose securely clamped down?

 

I cleared the codes, and P0420 came back. P2111 situation happened after cleaning the TB for the original problem and went away after dislodging that cotton string. I also replaced the original MAF when I was cleaning the TB. Acceleration is now the same as after I replaced the O2 sensor, but still have some idling issues, especially when the A/C is on or the radiator fan kicks on for coolant temp. The jerking has settled down too, and appears rarely now like before. (Post-O2 sensor replacement) I made sure to secure the intake hose.

I noticed that the jerking (when it does appear) is not as violent as before, but softer, and now affects the lower rpm range more than the higher range, in contrast to my first post.

I will try to find time to get myself under my car and check the front cat.

 

Honestly I have the same issue, my cat is removed myself but didn't have any issues with my cat removed, I think we have dirty fuel injectors

 

Alright guys, sorry for taking two entire months to finally close the case. I took my car to a muffler shops where they had the exhaust system tested and the mechanic said there is a chance replacing the front cat may not solve my problem. I chose to replace it anyways, and lo and behold, the jerking and poor acceleration is gone. On a related note, he said my resonator is bad but I'm satisfied with the end result anyways. Thank you everyone for voicing your opinions/suggestions.

 

Yep, bad (probably plugged up) cat will cause the symptoms you experienced. I learned this by experience fixing a Mazda/Ford which was behaving strangely. Turned out to be a completely plugged up cat.

 

Glad to hear that you got it sorted out.
I am having the same issue with my Matrix p0420 code and thinking of doing the same and replace the cats.

What mileage is your vehicle at?

 

Glad to hear that you got it sorted out.
I am having the same issue with my Matrix p0420 code and thinking of doing the same and replace the cats.

What mileage is your vehicle at?

My Corolla is at 158k

 

Wow low miles. Mines 188k no cat issues yet. I check every other year and the mesh is good still.
Maybe you can clean out the entire intake not sure why you have debris in it.

The cleaner the intake the better. No need to burn out a cat that quick.


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