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Discussion Starter #1
I just bought a 2002 Highlander, 2wd, v6, 156k miles. The check engine light was on for P1155 and P1135. I replaced B1S1 and B2S2 with new Denso 89467-48011 AF sensors. Now when accelerating I get a pulsing hesitation, most noticeably in 3rd gear. I've read the cause could be dirty injectors or MAF sensor. The thing that doesn't make sense is it was running fine before with the bad AF sensors. I left the battery unplugged overnight thinking the computer needs to relearn with the new sensors but it still the same. I've driven less than 10 miles since the new sensors, should I just give it more time? Thank you
 

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Get a can of MAF sensor cleaner and clean the sensor. Just don't touch the element. Unplug the electrical plug, Remove MAF sensor, spray, allow to air dry for 10-15 minutes, replace and replug. Then see what happens.

BTW have you checked your air filter and throttle body since you bought it? You might want to clean the TB and replace the filter if it's dirty. Double check your vacuum hoses as well.
 

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Discussion Starter #3 (Edited)
Get a can of MAF sensor cleaner and clean the sensor. Just don't touch the element. Unplug the electrical plug, Remove MAF sensor, spray, allow to air dry for 10-15 minutes, replace and replug. Then see what happens.

BTW have you checked your air filter and throttle body since you bought it? You might want to clean the TB and replace the filter if it's dirty. Double check your vacuum hoses as well.
So I replaced the MAF sensor (p/n 22204-22010).
I cleaned the throttle body.
Made sure the IAC sensor was clean.
Replaced the PVC valve (p/n 2002-2006).
Found one disconnected vacuum hose.

Got everything back together and the pulsing hesitation while accelerating is still present. Could it be the new O2 sensors I replaced even though they checked out good and aren't throwing any codes?

Thank for any ideas...
 

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I guess the O2 sensors could be bad but most likely not. What is the rpm range for the hesitation? Is it only in 3rd gear? If you hold the vehicle in 2nd gear manually and run up past that rpm range does it still hesitate?

I would double check your vacuum lines, air intake boot over the throttle body. Then look at fuel pump, and or transmission issue.

BTW the sensors you got the code on are Air/fuel ration sensors and NOT O2 exhaust sensors are you certain you got the correct ones? They should be bank one and two.

Checked the part numbers...you have the correct sensors. Drive it for a while and see if the codes return. Have you checked your transmission fluid? You should have the 1MZFE V6 and a U140E,140F or 241E four speed. It should have a dip stick on a 2002 IIRC. That year should still be on T-IV ATF. Double check your atf level when hot with the engine running and again dead cold with the engine off. There might be hot and cold marks on the dipstick. See if the ATF is brown and burned.
 

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Did you compare part numbers between the old and new o2 sensors. If youres has california emmisions its a different sensor. We have had a couple of shops here in NC that have run into this and drives them crazy till they figure out that the vehicle has Calif emissions.

Sent from my VS996 using Tapatalk
 

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Did you compare part numbers between the old and new o2 sensors. If youres has california emmisions its a different sensor. We have had a couple of shops here in NC that have run into this and drives them crazy till they figure out that the vehicle has Calif emissions.

Sent from my VS996 using Tapatalk
Would that show up on a vin check?
 

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Would that show up on a vin check?
I'm not sure on that, I don't know if the emissions sticker under the hood says anything about that or how they figured it out. I don't know if you could research youre vin and see where youre vehicle was originally sold or not. I'm thinking they just cross referenced part numbers but I could be wrong.

Sent from my VS996 using Tapatalk
 

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Discussion Starter #8
Did you compare part numbers between the old and new o2 sensors. If youres has california emmisions its a different sensor. We have had a couple of shops here in NC that have run into this and drives them crazy till they figure out that the vehicle has Calif emissions.

Sent from my VS996 using Tapatalk
Good suggestion but the part numbers between the old and new sensors are the same.
 

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Discussion Starter #9
I guess the O2 sensors could be bad but most likely not. What is the rpm range for the hesitation? Is it only in 3rd gear? If you hold the vehicle in 2nd gear manually and run up past that rpm range does it still hesitate?

I would double check your vacuum lines, air intake boot over the throttle body. Then look at fuel pump, and or transmission issue.

BTW the sensors you got the code on are Air/fuel ration sensors and NOT O2 exhaust sensors are you certain you got the correct ones? They should be bank one and two.

Checked the part numbers...you have the correct sensors. Drive it for a while and see if the codes return. Have you checked your transmission fluid? You should have the 1MZFE V6 and a U140E,140F or 241E four speed. It should have a dip stick on a 2002 IIRC. That year should still be on T-IV ATF. Double check your atf level when hot with the engine running and again dead cold with the engine off. There might be hot and cold marks on the dipstick. See if the ATF is brown and burned.
I'll double check vacuum sensors and check transmission fluid. It's just weird that it wasn't doing it before changing the AF sensors...
 

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Discussion Starter #13
I did some more tests today and only gets the pulsing hesitation between 2-3k RPM in 2nd gear it's noticable. In 3rd it's not very noticible but still there between 2-3K RPM.



The transaxle fluid looks & smells clean. It is a little low so I'll top it off soon. The tachometer pulses with the hesitation so if it was the trans slipping I would think the tach would stay smooth through the acceleration regardless of the trans?
 

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Discussion Starter #14
Watch this video. You might want to simply have your sensors checked like this guy does. That way you eliminate any AF sensor issues.
Interesting video. I unplugged an AF sensor and went for a test drive. I did still notice the same pulsing hesitation while accelerating but not as pronounced. Maybe because the car is running richer?
 

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since you have the plugs, why not swap them out to rule them out as a possible cause? Spark plugs generally cause a miss during acceleration because it's harder for a weaker spark to bridge the gap in higher compression you get when you apply more throttle.
of course if your pulse is what I would consider a pulse, more elongated and smoother, I might be barking up the wrong tree...
 

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Interesting video. I unplugged an AF sensor and went for a test drive. I did still notice the same pulsing hesitation while accelerating but not as pronounced. Maybe because the car is running richer?
I don't know but I would have a guy do a diagnostic to see if the AF sensors are performing as expected.
 

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Discussion Starter #17
Just finished replacing all the spark plugs. I took out some very old NGK BKR6E (made for a 90s 2.0L Corolla!) and replaced with Denso Iridium SK0R11. I don't know how it was running before... There's noticeably more power now. I notice the pulsing hesitation maybe half as much but it's still there. I'm waiting on a quart of ATF T-IV to top up the transmission and will report back.


Four of the ignition coils are cracked. I moved the worst ones to the front plugs for easy replacement in the future. This is the worst one:



 

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I couldn't get that picture up, but cracked coils could be a red flag. without seeing the picture, maybe I would suggest wrapping with electrical tape just to see if that helps if its feasible. If it makes a difference you know you need coils, but I would consider replacing the cracked ones anyway.
 
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